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Tabuena DR, Jang SS, Grone B, Yip O, Aery Jones EA, Blumenfeld J, Liang Z, Koutsodendris N, Rao A, Ding L, Zhang AR, Hao Y, Xu Q, Yoon SY, Leon SD, Huang Y, Zilberter M. Neuronal APOE4-induced Early Hippocampal Network Hyperexcitability in Alzheimer's Disease Pathogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.28.555153. [PMID: 37693533 PMCID: PMC10491126 DOI: 10.1101/2023.08.28.555153] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
The full impact of apolipoprotein E4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on neuronal and network function remains unclear. We found hippocampal region-specific network hyperexcitability in young APOE4 knock-in (E4-KI) mice which predicted cognitive deficits at old age. Network hyperexcitability in young E4-KI mice was mediated by hippocampal region-specific subpopulations of smaller and hyperexcitable neurons that were eliminated by selective removal of neuronal APOE4. Aged E4-KI mice exhibited hyperexcitable granule cells, a progressive inhibitory deficit, and E/I imbalance in the dentate gyrus, exacerbating hippocampal hyperexcitability. Single-nucleus RNA-sequencing revealed neuronal cell type-specific and age-dependent transcriptomic changes, including Nell2 overexpression in E4-KI mice. Reducing Nell2 expression in specific neuronal types of E4-KI mice with CRISPRi rescued their abnormal excitability phenotypes, implicating Nell2 overexpression as a cause of APOE4-induced hyperexcitability. These findings highlight the early transcriptomic and electrophysiological alterations underlying APOE4-induced hippocampal network dysfunction and its contribution to AD pathogenesis with aging.
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Nagarajan R, Lyu J, Kambali M, Wang M, Courtney CD, Christian-Hinman CA, Rudolph U. Genetic Ablation of Dentate Hilar Somatostatin-Positive GABAergic Interneurons is Sufficient to Induce Cognitive Impairment. Mol Neurobiol 2024; 61:567-580. [PMID: 37642935 PMCID: PMC11285310 DOI: 10.1007/s12035-023-03586-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 08/15/2023] [Indexed: 08/31/2023]
Abstract
Aging is often associated with a decline in cognitive function. A reduction in the number of somatostatin-positive (SOM+) interneurons in the dentate gyrus (DG) has been described in cognitively impaired but not in unimpaired aged rodents. However, it remains unclear whether the reduction in SOM + interneurons in the DG hilus is causal for age-related cognitive dysfunction. We hypothesized that hilar SOM+ interneurons play an essential role in maintaining cognitive function and that a reduction in the number of hilar SOM + interneurons might be sufficient to induce cognitive dysfunction. Hilar SOM+ interneurons were ablated by expressing a diphtheria toxin transgene specifically in these interneurons, which resulted in a reduction in the number of SOM+ /GAD-67+ neurons and dendritic spine density in the DG. C-fos and Iba-1 immunostainings were increased in DG and CA3, but not CA1, and BDNF protein expression in the hippocampus was decreased. Behavioral testing showed a reduced recognition index in the novel object recognition test, decreased alternations in the Y maze test, and longer latencies and path lengths in the learning and reversal learning phases of the Morris water maze. Our results show that partial genetic ablation of SOM+ hilar interneurons is sufficient to increase activity in DG and CA3, as has been described to occur with aging and to induce an impairment of learning and memory functions. Thus, partial ablation of hilar SOM + interneurons may be a significant contributing factor to age-related cognitive dysfunction. These mice may also be useful as a cellularly defined model of hippocampal aging.
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Affiliation(s)
- Rajasekar Nagarajan
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jinrui Lyu
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Maltesh Kambali
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Muxiao Wang
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Connor D Courtney
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Catherine A Christian-Hinman
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Uwe Rudolph
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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Hernandez AR, Barrett ME, Lubke KN, Maurer AP, Burke SN. A long-term ketogenic diet in young and aged rats has dissociable effects on prelimbic cortex and CA3 ensemble activity. Front Aging Neurosci 2023; 15:1274624. [PMID: 38155737 PMCID: PMC10753023 DOI: 10.3389/fnagi.2023.1274624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 11/20/2023] [Indexed: 12/30/2023] Open
Abstract
Introduction Age-related cognitive decline has been linked to distinct patterns of cellular dysfunction in the prelimbic cortex (PL) and the CA3 subregion of the hippocampus. Because higher cognitive functions require both structures, selectively targeting a neurobiological change in one region, at the expense of the other, is not likely to restore normal behavior in older animals. One change with age that both the PL and CA3 share, however, is a reduced ability to utilize glucose, which can produce aberrant neural activity patterns. Methods The current study used a ketogenic diet (KD) intervention, which reduces the brain's reliance on glucose, and has been shown to improve cognition, as a metabolic treatment for restoring neural ensemble dynamics in aged rats. Expression of the immediate-early genes Arc and Homer1a were used to quantify the neural ensembles that were active in the home cage prior to behavior, during a working memory/biconditional association task, and a continuous spatial alternation task. Results Aged rats on the control diet had increased activity in CA3 and less ensemble overlap in PL between different task conditions than did the young animals. In the PL, the KD was associated with increased activation of neurons in the superficial cortical layers, establishing a clear link between dietary macronutrient content and frontal cortical activity. The KD did not lead to any significant changes in CA3 activity. Discussion These observations suggest that the availability of ketone bodies may permit the engagement of compensatory mechanisms in the frontal cortices that produce better cognitive outcomes.
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Affiliation(s)
- Abbi R. Hernandez
- Division of Gerontology, Geriatrics, and Palliative Care, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, United States
| | - Maya E. Barrett
- Department of Psychology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Katelyn N. Lubke
- Department of Neuroscience, McKnight Brain Institute, and Center for Cognitive Aging and Memory, University of Florida, Gainesville, FL, United States
| | - Andrew P. Maurer
- Department of Neuroscience, McKnight Brain Institute, and Center for Cognitive Aging and Memory, University of Florida, Gainesville, FL, United States
| | - Sara N. Burke
- Department of Neuroscience, McKnight Brain Institute, and Center for Cognitive Aging and Memory, University of Florida, Gainesville, FL, United States
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Bañuelos C, Kittleson JR, LaNasa KH, Galiano CS, Roth SM, Perez EJ, Long JM, Roberts MT, Fong S, Rapp PR. Cognitive Aging and the Primate Basal Forebrain Revisited: Disproportionate GABAergic Vulnerability Revealed. J Neurosci 2023; 43:8425-8441. [PMID: 37798131 PMCID: PMC10711728 DOI: 10.1523/jneurosci.0456-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 09/22/2023] [Accepted: 09/23/2023] [Indexed: 10/07/2023] Open
Abstract
Basal forebrain (BF) projections to the hippocampus and cortex are anatomically positioned to influence a broad range of cognitive capacities that are known to decline in normal aging, including executive function and memory. Although a long history of research on neurocognitive aging has focused on the role of the cholinergic basal forebrain system, intermingled GABAergic cells are numerically as prominent and well positioned to regulate the activity of their cortical projection targets, including the hippocampus and prefrontal cortex. The effects of aging on noncholinergic BF neurons in primates, however, are largely unknown. In this study, we conducted quantitative morphometric analyses in brains from young adult (6 females, 2 males) and aged (11 females, 5 males) rhesus monkeys (Macaca mulatta) that displayed significant impairment on standard tests that require the prefrontal cortex and hippocampus. Cholinergic (ChAT+) and GABAergic (GAD67+) neurons were quantified through the full rostrocaudal extent of the BF. Total BF immunopositive neuron number (ChAT+ plus GAD67+) was significantly lower in aged monkeys compared with young, largely because of fewer GAD67+ cells. Additionally, GAD67+ neuron volume was greater selectively in aged monkeys without cognitive impairment compared with young monkeys. These findings indicate that the GABAergic component of the primate BF is disproportionally vulnerable to aging, implying a loss of inhibitory drive to cortical circuitry. Moreover, adaptive reorganization of the GABAergic circuitry may contribute to successful neurocognitive outcomes.SIGNIFICANCE STATEMENT A long history of research has confirmed the role of the basal forebrain in cognitive aging. The majority of that work has focused on BF cholinergic neurons that innervate the cortical mantle. Codistributed BF GABAergic populations are also well positioned to influence cognitive function, yet little is known about this prominent neuronal population in the aged brain. In this unprecedented quantitative comparison of both cholinergic and GABAergic BF neurons in young and aged rhesus macaques, we found that neuron number is significantly reduced in the aged BF compared with young, and that this reduction is disproportionately because of a loss of GABAergic neurons. Together, our findings encourage a new perspective on the functional organization of the primate BF in neurocognitive aging.
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Affiliation(s)
- Cristina Bañuelos
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Joshua R Kittleson
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Katherine H LaNasa
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Christina S Galiano
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Stephanie M Roth
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Evelyn J Perez
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Jeffrey M Long
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
| | - Mary T Roberts
- California National Primate Research Center, University of California, Davis, Davis, California 95616
| | - Sania Fong
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
- California National Primate Research Center, University of California, Davis, Davis, California 95616
| | - Peter R Rapp
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, Maryland 21224
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Gray DT, Zempare M, Carey N, Khattab S, Sinakevitch I, De Biase LM, Barnes CA. Extracellular matrix proteoglycans support aged hippocampus networks: a potential cellular-level mechanism of brain reserve. Neurobiol Aging 2023; 131:52-58. [PMID: 37572527 PMCID: PMC10529564 DOI: 10.1016/j.neurobiolaging.2023.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 07/12/2023] [Accepted: 07/14/2023] [Indexed: 08/14/2023]
Abstract
One hallmark of normative brain aging is vast heterogeneity in whether older people succumb to or resist cognitive decline. Resilience describes a brain's capacity to maintain cognition in the face of aging and disease. One factor influencing resilience is brain reserve-the status of neurobiological resources available to support neuronal circuits as dysfunction accumulates. This study uses a cohort of behaviorally characterized adult, middle-aged, and aged rats to test whether neurobiological factors that protect inhibitory neurotransmission and synapse function represent key components of brain reserve. Histochemical analysis of extracellular matrix proteoglycans, which play critical roles in stabilizing synapses and modulating inhibitory neuron excitability, was conducted alongside analyses of lipofuscin-associated autofluorescence. The findings indicate that aging results in lower proteoglycan density and more lipofuscin in CA3. Aged rats with higher proteoglycan density exhibited better performance on the Morris watermaze, whereas lipofuscin abundance was not related to spatial memory. These data suggest that the local environment around neurons may protect against synapse dysfunction or hyperexcitability and could contribute to brain reserve mechanisms.
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Affiliation(s)
- Daniel T Gray
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Marc Zempare
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA
| | - Natalie Carey
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA
| | - Salma Khattab
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA
| | - Irina Sinakevitch
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA
| | - Lindsay M De Biase
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Carol A Barnes
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA; Departments of Psychology, Neurology and Neuroscience, University of Arizona, Tucson, AZ, USA.
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Case SL, Lin R, Thibault O. Age- and sex-dependent alterations in primary somatosensory cortex neuronal calcium network dynamics during locomotion. Aging Cell 2023; 22:e13898. [PMID: 37269157 PMCID: PMC10410056 DOI: 10.1111/acel.13898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 05/12/2023] [Accepted: 05/22/2023] [Indexed: 06/04/2023] Open
Abstract
Over the past 30 years, the calcium (Ca2+ ) hypothesis of brain aging has provided clear evidence that hippocampal neuronal Ca2+ dysregulation is a key biomarker of aging. Age-dependent Ca2+ -mediated changes in intrinsic excitability, synaptic plasticity, and activity have helped identify some of the mechanisms engaged in memory and cognitive decline based on work done mostly at the single-cell level and in the slice preparation. Recently, our lab identified age- and Ca2+ -related neuronal network dysregulation in the cortex of the anesthetized animal. Still, investigations in the awake animal are needed to test the generalizability of the Ca2+ hypothesis of brain aging. Here, we used in vigilo two-photon imaging in ambulating mice, to image GCaMP8f in the primary somatosensory cortex (S1), during ambulation and at rest. We investigated aging- and sex-related changes in neuronal networks in the C56BL/6J mouse. Following imaging, gait behavior was characterized to test for changes in locomotor stability. During ambulation, in both young adult and aged mice, an increase in network connectivity and synchronicity was noted. An age-dependent increase in synchronicity was seen in ambulating aged males only. Additionally, females displayed increases in the number of active neurons, Ca2+ transients, and neuronal activity compared to males, particularly during ambulation. These results suggest S1 Ca2+ dynamics and network synchronicity are likely contributors of locomotor stability. We believe this work raises awareness of age- and sex-dependent alterations in S1 neuronal networks, perhaps underlying the increase in falls with age.
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Affiliation(s)
- Sami L. Case
- Department of Pharmacology & Nutritional SciencesUniversity of Kentucky College of MedicineLexingtonKentuckyUSA
| | - Ruei‐Lung Lin
- Department of Pharmacology & Nutritional SciencesUniversity of Kentucky College of MedicineLexingtonKentuckyUSA
| | - Olivier Thibault
- Department of Pharmacology & Nutritional SciencesUniversity of Kentucky College of MedicineLexingtonKentuckyUSA
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Gray DT, Khattab S, Meltzer J, McDermott K, Schwyhart R, Sinakevitch I, Härtig W, Barnes CA. Retrosplenial cortex microglia and perineuronal net densities are associated with memory impairment in aged rhesus macaques. Cereb Cortex 2023; 33:4626-4644. [PMID: 36169578 PMCID: PMC10110451 DOI: 10.1093/cercor/bhac366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 08/18/2022] [Accepted: 08/22/2022] [Indexed: 11/13/2022] Open
Abstract
Synapse loss and altered plasticity are significant contributors to memory loss in aged individuals. Microglia, the innate immune cells of the brain, play critical roles in maintaining synapse function, including through a recently identified role in regulating the brain extracellular matrix. This study sought to determine the relationship between age, microglia, and extracellular matrix structure densities in the macaque retrosplenial cortex. Twenty-nine macaques ranging in age from young adult to aged were behaviorally characterized on 3 distinct memory tasks. Microglia, parvalbumin (PV)-expressing interneurons and extracellular matrix structures, known as perineuronal nets (PNNs), were immuno- and histochemically labeled. Our results indicate that microglia densities increase in the retrosplenial cortex of aged monkeys, while the proportion of PV neurons surrounded by PNNs decreases. Aged monkeys with more microglia had fewer PNN-associated PV neurons and displayed slower learning and poorer performance on an object recognition task. Stepwise regression models using age and the total density of aggrecan, a chondroitin sulfate proteoglycan of PNNs, better predicted memory performance than did age alone. Together, these findings indicate that elevated microglial activity in aged brains negatively impacts cognition in part through mechanisms that alter PNN assembly in memory-associated brain regions.
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Affiliation(s)
- Daniel T Gray
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ 85721, United States
| | - Salma Khattab
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ 85721, United States
| | - Jeri Meltzer
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ 85721, United States
| | - Kelsey McDermott
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ 85721, United States
| | - Rachel Schwyhart
- Paul Flechsig Institute for Brain Research, University of Leipzig, Leipzig 04103, Germany
| | - Irina Sinakevitch
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ 85721, United States
| | - Wolfgang Härtig
- Paul Flechsig Institute for Brain Research, University of Leipzig, Leipzig 04103, Germany
| | - Carol A Barnes
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ 85721, United States
- Departments of Psychology, Neurology and Neuroscience, University of Arizona, Tucson, AZ 85721, United States
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Hernandez AR, Barrett ME, Lubke KN, Maurer AP, Burke SN. A long-term ketogenic diet in young and aged rats has dissociable effects on prelimbic cortex and CA3 ensemble activity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.18.529095. [PMID: 36824737 PMCID: PMC9949134 DOI: 10.1101/2023.02.18.529095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Age-related cognitive decline has been linked to distinct patterns of cellular dysfunction in the prelimbic cortex (PL) and the CA3 subregion of the hippocampus. Because higher cognitive functions require both structures, selectively targeting a neurobiological change in one region, at the expense of the other, is not likely to restore normal behavior in older animals. One change with age that both the PL and CA3 share, however, is a reduced ability to utilize glucose, which can produce aberrant neural activity patterns. The current study used a ketogenic diet (KD) intervention, which reduces the brain’s reliance on glucose, and has been shown to improve cognition, as a metabolic treatment for restoring neural ensemble dynamics in aged rats. Expression of the immediate-early genes Arc and Homer 1a were used to quantify the neural ensembles that were active in the home cage prior to behavior, during a working memory/biconditional association task, and a continuous spatial alternation task. Aged rats on the control diet had increased activity in CA3 and less ensemble overlap in PL between different task conditions than did the young animals. In the PL, the KD was associated with increased activation of neurons in the superficial cortical layers. The KD did not lead to any significant changes in CA3 activity. These observations suggest that the KD does not restore neuron activation patterns in aged animals, but rather the availability of ketone bodies in the frontal cortices may permit the engagement of compensatory mechanisms that produce better cognitive outcomes. Significance Statement This study extends understanding of how a ketogenic diet (KD) intervention may improve cognitive function in older adults. Young and aged rats were given 3 months of a KD or a calorie-match control diet and then expression of the immediate-early genes Arc and Homer 1a were measured to examine neural ensemble dynamics during cognitive testing. The KD diet was associated with increased activation of neurons in the superficial layers of the PL, but there were no changes in CA3. These observations are significant because they suggest that compensatory mechanisms for improving cognition are engaged in the presence of elevated ketone bodies. This metabolic shift away from glycolysis can meet the energetic needs of the frontal cortices when glucose utilization is compromised.
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Zhou R, Belge T, Wolbers T. Reaching the Goal: Superior Navigators in Late Adulthood Provide a Novel Perspective into Successful Cognitive Aging. Top Cogn Sci 2023; 15:15-45. [PMID: 35582831 DOI: 10.1111/tops.12608] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 02/01/2023]
Abstract
Normal aging is typically associated with declines in navigation and spatial memory abilities. However, increased interindividual variability in performance across various navigation/spatial memory tasks is also evident with advancing age. In this review paper, we shed the spotlight on those older individuals who exhibit exceptional, sometimes even youth-like navigational/spatial memory abilities. Importantly, we (1) showcase observations from existing studies that demonstrate superior navigation/spatial memory performance in late adulthood, (2) explore possible cognitive correlates and neurophysiological mechanisms underlying these preserved spatial abilities, and (3) discuss the potential link between the superior navigators in late adulthood and SuperAgers (older adults with superior episodic memory). In the closing section, given the lack of studies that directly focus on this subpopulation, we highlight several important directions that future studies could look into to better understand the cognitive characteristics of older superior navigators and the factors enabling such successful cognitive aging.
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Affiliation(s)
- Ruojing Zhou
- Aging, Cognition and Technology Lab, German Center for Neurodegenerative Diseases
| | - Tuğçe Belge
- Aging, Cognition and Technology Lab, German Center for Neurodegenerative Diseases
| | - Thomas Wolbers
- Aging, Cognition and Technology Lab, German Center for Neurodegenerative Diseases.,Center for Behavioral Brain Sciences, Magdeburg
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DiCola NM, Lacy AL, Bishr OJ, Kimsey KM, Whitney JL, Lovett SD, Burke SN, Maurer AP. Advanced age has dissociable effects on hippocampal CA1 ripples and CA3 high frequency events in male rats. Neurobiol Aging 2022; 117:44-58. [PMID: 35665647 PMCID: PMC9392897 DOI: 10.1016/j.neurobiolaging.2022.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 02/01/2023]
Abstract
Sharp wave/ripples/high frequency events (HFEs) are transient bursts of depolarization in hippocampal subregions CA3 and CA1 that occur during rest and pauses in behavior. Previous studies have reported that CA1 ripples in aged rats have lower frequency than those detected in young animals. While CA1 ripples are thought to be driven by CA3, HFEs in CA3 have not been examined in aged animals. The current study obtained simultaneous recordings from CA1 and CA3 in young and aged rats to examine sharp wave/ripples/HFEs in relation to age. While CA1 ripple frequency was reduced with age, there were no age differences in the frequency of CA3 HFEs, although power and length were lower in old animals. While there was a proportion of CA1 ripples that co-occurred with a CA3 HFE, none of the age-related differences in CA1 ripples could be explained by alterations in CA3 HFE characteristics. These findings suggest that age differences in CA1 are not due to altered CA3 activity, but instead reflect distinct mechanisms of ripple generation with age.
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Affiliation(s)
- Nicholas M. DiCola
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Alexa L. Lacy
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Omar J. Bishr
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Kathryn M. Kimsey
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Jenna L. Whitney
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Sarah D. Lovett
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Sara N. Burke
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA,Corresponding author at: University of Florida, Neuroscience, McKnight Brain Institute, P.O. Box 100244, 1149 Newell Dr, RM L1-100G, Gainesville, FL 32610, USA. (S.N. Burke)
| | - Andrew P. Maurer
- Evelyn F. McKnight McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL, USA,Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA,Engineering School of Sustainable Infrastructure and Environment, University of Florida, Gainesville, FL, USA,Corresponding author at: McKnight Brain Institute, 1149 Newell Dr, RM L1-100E, University of Florida, Gainesville, FL 32610, USA. (A.P. Maurer)
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Canatelli-Mallat M, Chiavellini P, Lehmann M, Goya RG, Morel GR. AGE-RELATED LOSS OF RECOGNITION MEMORY AND ITS CORRELATION WITH HIPPOCAMPAL AND PERIRHINAL CORTEX CHANGES IN FEMALE SPRAGUE-DAWLEY RATS. Behav Brain Res 2022; 435:114026. [DOI: 10.1016/j.bbr.2022.114026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/20/2022] [Accepted: 07/24/2022] [Indexed: 11/02/2022]
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Cooper TL, Thompson JJ, Turner SM, Watson C, Lubke KN, Logan CN, Maurer AP, Burke SN. Unilateral Perforant Path Transection Does Not Alter Lateral Entorhinal Cortical or Hippocampal CA3 Arc Expression. Front Syst Neurosci 2022; 16:920713. [PMID: 35844245 PMCID: PMC9279555 DOI: 10.3389/fnsys.2022.920713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 06/13/2022] [Indexed: 11/13/2022] Open
Abstract
It is well established that degradation of perforant path fibers is associated with age-related cognitive dysfunction and CA3 hyperactivity. Whether this fiber loss triggers a cascade of other functional changes within the hippocampus circuit has not been causatively established, however. Thus, the current study evaluated the effect of perforant path fiber loss on neuronal activity in CA3 and layer II of the lateral entorhinal cortex (LEC) in relation to mnemonic similarity task performance. Expression of the immediate early gene Arc was quantified in rats that received a unilateral right hemisphere transection of the perforant path or sham surgery that cut the cortex but left the fibers intact. Behavior-related expression of Arc mRNA was measured to test the hypothesis that fiber loss leads to elevated activation of CA3 and LEC neurons, as previously observed in aged rats that were impaired on the mnemonic similarity task. Transection of perforant path fibers, which has previously been shown to lead to a decline in mnemonic similarity task performance, did not alter Arc expression. Arc expression in CA3, however, was correlated with task performance on the more difficult discrimination trials across both surgical groups. These observations further support a link between CA3 activity and mnemonic similarity task performance but suggest the reduced input from the entorhinal cortex to the hippocampus, as observed in old age, does not causatively elevate CA3 activity.
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Affiliation(s)
- Tara L. Cooper
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
- Graduate Program in Biomedical Sciences, Neuroscience Concentration, University of Florida, Gainesville, FL, United States
| | - John J. Thompson
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Sean M. Turner
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Cory Watson
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Katelyn N. Lubke
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Carly N. Logan
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Andrew P. Maurer
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Sara N. Burke
- Department of Neuroscience, Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
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13
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Lee H, Wang Z, Tillekeratne A, Lukish N, Puliyadi V, Zeger S, Gallagher M, Knierim JJ. Loss of functional heterogeneity along the CA3 transverse axis in aging. Curr Biol 2022; 32:2681-2693.e4. [PMID: 35597233 PMCID: PMC9233142 DOI: 10.1016/j.cub.2022.04.077] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 04/18/2022] [Accepted: 04/26/2022] [Indexed: 01/05/2023]
Abstract
Age-related deficits in pattern separation have been postulated to bias the output of hippocampal memory processing toward pattern completion, which can cause deficits in accurate memory retrieval. Although the CA3 region of the hippocampus is often conceptualized as a homogeneous network involved in pattern completion, growing evidence demonstrates a functional gradient in CA3 along the transverse axis, as pattern-separated outputs (dominant in the more proximal CA3) transition to pattern-completed outputs (dominant in the more distal CA3). We examined the neural representations along the CA3 transverse axis in young (Y), aged memory-unimpaired (AU), and aged memory-impaired (AI) rats when different changes were made to the environment. Functional heterogeneity in CA3 was observed in Y and AU rats when the environmental similarity was high (altered cues or altered environment shapes in the same room), with more orthogonalized representations in proximal CA3 than in distal CA3. In contrast, AI rats showed reduced orthogonalization in proximal CA3 but showed normal (i.e., generalized) representations in distal CA3, with little evidence of a functional gradient. Under experimental conditions when the environmental similarity was low (different rooms), representations in proximal and distal CA3 remapped in all rats, showing that CA3 of AI rats is able to encode distinctive representations for inputs with greater dissimilarity. These experiments support the hypotheses that the age-related bias toward hippocampal pattern completion is due to the loss in AI rats of the normal transition from pattern separation to pattern completion along the CA3 transverse axis.
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Affiliation(s)
- Heekyung Lee
- Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, 21218,Correspondence: ;
| | - Zitong Wang
- Department of Biostatistics, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, 21205
| | - Arjuna Tillekeratne
- Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, 21218
| | - Nick Lukish
- Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, 21218
| | - Vyash Puliyadi
- Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, 21218,Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD
| | - Scott Zeger
- Department of Biostatistics, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, 21205
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD,Kavli Neuroscience Discovery Institute, Johns Hopkins University
| | - James J. Knierim
- Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, 21218,Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD,Kavli Neuroscience Discovery Institute, Johns Hopkins University,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205,Lead Contact,Correspondence: ;
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14
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Lin RL, Frazier HN, Anderson KL, Case SL, Ghoweri AO, Thibault O. Sensitivity of the S1 neuronal calcium network to insulin and Bay-K 8644 in vivo: Relationship to gait, motivation, and aging processes. Aging Cell 2022; 21:e13661. [PMID: 35717599 PMCID: PMC9282843 DOI: 10.1111/acel.13661] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 05/10/2022] [Accepted: 06/05/2022] [Indexed: 01/25/2023] Open
Abstract
Neuronal hippocampal Ca2+ dysregulation is a critical component of cognitive decline in brain aging and Alzheimer's disease and is suggested to impact communication and excitability through the activation of a larger after hyperpolarization. However, few studies have tested for the presence of Ca2+ dysregulation in vivo, how it manifests, and whether it impacts network function across hundreds of neurons. Here, we tested for neuronal Ca2+ network dysregulation in vivo in the primary somatosensory cortex (S1) of anesthetized young and aged male Fisher 344 rats using single‐cell resolution techniques. Because S1 is involved in sensory discrimination and proprioception, we tested for alterations in ambulatory performance in the aged animal and investigated two potential pathways underlying these central aging‐ and Ca2+‐dependent changes. Compared to young, aged animals displayed increased overall activity and connectivity of the network as well as decreased ambulatory speed. In aged animals, intranasal insulin (INI) increased network synchronicity and ambulatory speed. Importantly, in young animals, delivery of the L‐type voltage‐gated Ca2+ channel modifier Bay‐K 8644 altered network properties, replicating some of the changes seen in the older animal. These results suggest that hippocampal Ca2+ dysregulation may be generalizable to other areas, such as S1, and might engage modalities that are associated with locomotor stability and motivation to ambulate. Further, given the safety profile of INI in the clinic and the evidence presented here showing that this central dysregulation is sensitive to insulin, we suggest that these processes can be targeted to potentially increase motivation and coordination while also reducing fall frequency with age.
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Affiliation(s)
- Ruei-Lung Lin
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Hilaree N Frazier
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Katie L Anderson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Sami L Case
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Adam O Ghoweri
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Olivier Thibault
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
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15
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Hernandez CM, Hernandez AR, Hoffman JM, King PH, McMahon LL, Buford TW, Carter C, Bizon JL, Burke SN. A Neuroscience Primer for Integrating Geroscience With the Neurobiology of Aging. J Gerontol A Biol Sci Med Sci 2022; 77:e19-e33. [PMID: 34623396 PMCID: PMC8751809 DOI: 10.1093/gerona/glab301] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Indexed: 11/13/2022] Open
Abstract
Neuroscience has a rich history of studies focusing on neurobiology of aging. However, much of the aging studies in neuroscience occur outside of the gerosciences. The goal of this primer is 2-fold: first, to briefly highlight some of the history of aging neurobiology and second, to introduce to geroscientists the broad spectrum of methodological approaches neuroscientists use to study the neurobiology of aging. This primer is accompanied by a corresponding geroscience primer, as well as a perspective on the current challenges and triumphs of the current divide across these 2 fields. This series of manuscripts is intended to foster enhanced collaborations between neuroscientists and geroscientists with the intent of strengthening the field of cognitive aging through inclusion of parameters from both areas of expertise.
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Affiliation(s)
- Caesar M Hernandez
- Department of Cellular, Development, and Integrative Biology, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Evelyn F. McKnight Brain Institute, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Abigail R Hernandez
- Evelyn F. McKnight Brain Institute, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jessica M Hoffman
- Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Peter H King
- Department of Cellular, Development, and Integrative Biology, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Department of Neurology, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Birmingham Veterans Affairs Medical Center, Birmingham, Alabama, USA
| | - Lori L McMahon
- Department of Cellular, Development, and Integrative Biology, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Evelyn F. McKnight Brain Institute, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,UAB Nathan Shock Center for the Basic Biology of Aging, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,UAB Integrative Center for Aging Research, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Thomas W Buford
- Evelyn F. McKnight Brain Institute, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,UAB Nathan Shock Center for the Basic Biology of Aging, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,UAB Integrative Center for Aging Research, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Geriatric Research Education and Clinical Center, Birmingham VA Medical Center, Birmingham, Alabama, USA
| | - Christy Carter
- Evelyn F. McKnight Brain Institute, The University of Alabama at Birmingham, Birmingham, Alabama, USA.,Department of Medicine, Division of Gerontology, Geriatrics, and Palliative Care, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Jennifer L Bizon
- Department of Neuroscience, Center for Cognitive Aging and Memory, and the McKnight Brain Institute, The University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Sara N Burke
- Department of Neuroscience, Center for Cognitive Aging and Memory, and the McKnight Brain Institute, The University of Florida, College of Medicine, Gainesville, Florida, USA
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16
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Tran TT, Speck CL, Gallagher M, Bakker A. Lateral Entorhinal Cortex Dysfunction in Amnestic Mild Cognitive Impairment. Neurobiol Aging 2021; 112:151-160. [PMID: 35182842 PMCID: PMC8976714 DOI: 10.1016/j.neurobiolaging.2021.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 12/24/2021] [Accepted: 12/26/2021] [Indexed: 11/16/2022]
Abstract
The entorhinal cortex is the site of some of the earliest pathological changes in Alzheimer's disease, including neuronal, synaptic and volumetric loss. Specifically, the lateral entorhinal cortex shows significant accumulation of tau neurofibrillary tangles in the amnestic mild cognitive impairment (aMCI) phase of Alzheimer's disease. Although decreased entorhinal cortex activation has been observed in patients with aMCI in the context of impaired memory function, it remains unclear if functional changes in the entorhinal cortex can be localized to the lateral or medial entorhinal cortex. To assess subregion specific changes in the lateral and medial entorhinal cortex, patients with aMCI and healthy aged-matched control participants underwent high-resolution structural and functional magnetic resonance imaging. Patients with aMCI showed significantly reduced volume, and decreased activation localized to the lateral entorhinal cortex but not the medial entorhinal cortex. These results show that structural and functional changes associated with impaired memory function differentially engage the lateral entorhinal cortex in patients with aMCI, consistent with the locus of early disease related pathology.
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Affiliation(s)
- Tammy T Tran
- Department of Psychological and Brain Sciences, Johns Hopkins University School of Arts and Sciences, Baltimore, MD, USA
| | - Caroline L Speck
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University School of Arts and Sciences, Baltimore, MD, USA
| | - Arnold Bakker
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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17
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Diersch N, Valdes-Herrera JP, Tempelmann C, Wolbers T. Increased Hippocampal Excitability and Altered Learning Dynamics Mediate Cognitive Mapping Deficits in Human Aging. J Neurosci 2021; 41:3204-3221. [PMID: 33648956 PMCID: PMC8026345 DOI: 10.1523/jneurosci.0528-20.2021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 01/15/2021] [Accepted: 01/20/2021] [Indexed: 11/28/2022] Open
Abstract
Learning the spatial layout of a novel environment is associated with dynamic activity changes in the hippocampus and in medial parietal areas. With advancing age, the ability to learn spatial environments deteriorates substantially but the underlying neural mechanisms are not well understood. Here, we report findings from a behavioral and a fMRI experiment where healthy human older and younger adults of either sex performed a spatial learning task in a photorealistic virtual environment (VE). We modeled individual learning states using a Bayesian state-space model and found that activity in retrosplenial cortex (RSC)/parieto-occipital sulcus (POS) and anterior hippocampus did not change systematically as a function learning in older compared with younger adults across repeated episodes in the environment. Moreover, effective connectivity analyses revealed that the age-related learning deficits were linked to an increase in hippocampal excitability. Together, these results provide novel insights into how human aging affects computations in the brain's navigation system, highlighting the critical role of the hippocampus.SIGNIFICANCE STATEMENT Key structures of the brain's navigation circuit are particularly vulnerable to the deleterious consequences of aging, and declines in spatial navigation are among the earliest indicators for a progression from healthy aging to neurodegenerative diseases. Our study is among the first to provide a mechanistic account about how physiological changes in the aging brain affect the formation of spatial knowledge. We show that neural activity in the aging hippocampus and medial parietal areas is decoupled from individual learning states across repeated episodes in a novel spatial environment. Importantly, we find that increased excitability of the anterior hippocampus might constitute a potential neural mechanism for cognitive mapping deficits in old age.
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Affiliation(s)
- Nadine Diersch
- Aging and Cognition Research Group, German Center for Neurodegenerative Diseases (DZNE), Magdeburg 39120, Germany
| | - Jose P Valdes-Herrera
- Aging and Cognition Research Group, German Center for Neurodegenerative Diseases (DZNE), Magdeburg 39120, Germany
| | - Claus Tempelmann
- Department of Neurology, Otto-von-Guericke University Magdeburg, Magdeburg 39120, Germany
| | - Thomas Wolbers
- Aging and Cognition Research Group, German Center for Neurodegenerative Diseases (DZNE), Magdeburg 39120, Germany
- Department of Neurology, Otto-von-Guericke University Magdeburg, Magdeburg 39120, Germany
- Center for Behavioural Brain Sciences (CBBS), Otto-von-Guericke University Magdeburg, Magdeburg 39120, Germany
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18
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Buss EW, Corbett NJ, Roberts JG, Ybarra N, Musial TF, Simkin D, Molina-Campos E, Oh KJ, Nielsen LL, Ayala GD, Mullen SA, Farooqi AK, D'Souza GX, Hill CL, Bean LA, Rogalsky AE, Russo ML, Curlik DM, Antion MD, Weiss C, Chetkovich DM, Oh MM, Disterhoft JF, Nicholson DA. Cognitive aging is associated with redistribution of synaptic weights in the hippocampus. Proc Natl Acad Sci U S A 2021; 118:e1921481118. [PMID: 33593893 PMCID: PMC7923642 DOI: 10.1073/pnas.1921481118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Behaviors that rely on the hippocampus are particularly susceptible to chronological aging, with many aged animals (including humans) maintaining cognition at a young adult-like level, but many others the same age showing marked impairments. It is unclear whether the ability to maintain cognition over time is attributable to brain maintenance, sufficient cognitive reserve, compensatory changes in network function, or some combination thereof. While network dysfunction within the hippocampal circuit of aged, learning-impaired animals is well-documented, its neurobiological substrates remain elusive. Here we show that the synaptic architecture of hippocampal regions CA1 and CA3 is maintained in a young adult-like state in aged rats that performed comparably to their young adult counterparts in both trace eyeblink conditioning and Morris water maze learning. In contrast, among learning-impaired, but equally aged rats, we found that a redistribution of synaptic weights amplifies the influence of autoassociational connections among CA3 pyramidal neurons, yet reduces the synaptic input onto these same neurons from the dentate gyrus. Notably, synapses within hippocampal region CA1 showed no group differences regardless of cognitive ability. Taking the data together, we find the imbalanced synaptic weights within hippocampal CA3 provide a substrate that can explain the abnormal firing characteristics of both CA3 and CA1 pyramidal neurons in aged, learning-impaired rats. Furthermore, our work provides some clarity with regard to how some animals cognitively age successfully, while others' lifespans outlast their "mindspans."
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Affiliation(s)
- Eric W Buss
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Nicola J Corbett
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Joshua G Roberts
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Natividad Ybarra
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Timothy F Musial
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Dina Simkin
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | | | - Kwang-Jin Oh
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Lauren L Nielsen
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Gelique D Ayala
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Sheila A Mullen
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Anise K Farooqi
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Gary X D'Souza
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Corinne L Hill
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Linda A Bean
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Annalise E Rogalsky
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Matthew L Russo
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612
| | - Dani M Curlik
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Marci D Antion
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Craig Weiss
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Dane M Chetkovich
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - M Matthew Oh
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - John F Disterhoft
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
| | - Daniel A Nicholson
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612;
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19
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Heterogeneity of Age-Related Neural Hyperactivity along the CA3 Transverse Axis. J Neurosci 2021; 41:663-673. [PMID: 33257325 DOI: 10.1523/jneurosci.2405-20.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/12/2020] [Accepted: 11/19/2020] [Indexed: 02/08/2023] Open
Abstract
Age-related memory deficits are correlated with neural hyperactivity in the CA3 region of the hippocampus. Abnormal CA3 hyperactivity in aged rats has been proposed to contribute to an imbalance between pattern separation and pattern completion, resulting in overly rigid representations. Recent evidence of functional heterogeneity along the CA3 transverse axis suggests that proximal CA3 supports pattern separation while distal CA3 supports pattern completion. It is not known whether age-related CA3 hyperactivity is uniformly represented along the CA3 transverse axis. We examined the firing rates of CA3 neurons from young and aged, male, Long-Evans rats along the CA3 transverse axis. Consistent with prior studies, young CA3 cells showed an increasing gradient in mean firing rate from proximal to distal CA3. However, aged CA3 cells showed an opposite, decreasing trend, in that CA3 cells in aged rats were hyperactive in proximal CA3, but possibly hypoactive in distal CA3, compared with young (Y) rats. We suggest that, in combination with altered inputs from the entorhinal cortex and dentate gyrus (DG), the proximal CA3 region of aged rats may switch from its normal function that reflects the pattern separation output of the DG and instead performs a computation that reflects an abnormal bias toward pattern completion. In parallel, distal CA3 of aged rats may create weaker attractor basins that promote abnormal, bistable representations under certain conditions.SIGNIFICANCE STATEMENT Prior work suggested that age-related CA3 hyperactivity enhances pattern completion, resulting in rigid representations. Implicit in prior studies is the notion that hyperactivity is present throughout a functionally homogeneous CA3 network. However, more recent work has demonstrated functional heterogeneity along the CA3 transverse axis, in that proximal CA3 is involved in pattern separation and distal CA3 is involved in pattern completion. Here, we show that age-related hyperactivity is present only in proximal CA3, with potential hypoactivity in distal CA3. This result provides new insight in the role of CA3 in age-related memory impairments, suggesting that the rigid representations in aging result primarily from dysfunction of computational circuits involving the dentate gyrus (DG) and proximal CA3.
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20
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Hector A, Brouillette J. Hyperactivity Induced by Soluble Amyloid-β Oligomers in the Early Stages of Alzheimer's Disease. Front Mol Neurosci 2021; 13:600084. [PMID: 33488358 PMCID: PMC7817907 DOI: 10.3389/fnmol.2020.600084] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/01/2020] [Indexed: 12/12/2022] Open
Abstract
Soluble amyloid-beta oligomers (Aβo) start to accumulate in the human brain one to two decades before any clinical symptoms of Alzheimer's disease (AD) and are implicated in synapse loss, one of the best predictors of memory decline that characterize the illness. Cognitive impairment in AD was traditionally thought to result from a reduction in synaptic activity which ultimately induces neurodegeneration. More recent evidence indicates that in the early stages of AD synaptic failure is, at least partly, induced by neuronal hyperactivity rather than hypoactivity. Here, we review the growing body of evidence supporting the implication of soluble Aβo on the induction of neuronal hyperactivity in AD animal models, in vitro, and in humans. We then discuss the impact of Aβo-induced hyperactivity on memory performance, cell death, epileptiform activity, gamma oscillations, and slow wave activity. We provide an overview of the cellular and molecular mechanisms that are emerging to explain how Aβo induce neuronal hyperactivity. We conclude by providing an outlook on the impact of hyperactivity for the development of disease-modifying interventions at the onset of AD.
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Affiliation(s)
- Audrey Hector
- Department of Pharmacology and Physiology, Hôpital du Sacré-Cœur de Montréal Research Center, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Île-de-Montréal (CIUSSS-NIM), Université de Montréal, Montreal, QC, Canada
| | - Jonathan Brouillette
- Department of Pharmacology and Physiology, Hôpital du Sacré-Cœur de Montréal Research Center, Centre intégré universitaire de santé et de services sociaux du Nord-de-l'Île-de-Montréal (CIUSSS-NIM), Université de Montréal, Montreal, QC, Canada
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21
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Stark SM, Frithsen A, Stark CE. Age-related alterations in functional connectivity along the longitudinal axis of the hippocampus and its subfields. Hippocampus 2021; 31:11-27. [PMID: 32918772 PMCID: PMC8354549 DOI: 10.1002/hipo.23259] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 07/31/2020] [Accepted: 08/07/2020] [Indexed: 12/13/2022]
Abstract
Hippocampal circuit alterations that differentially affect hippocampal subfields are associated with age-related memory decline. Additionally, functional organization along the longitudinal axis of the hippocampus has revealed distinctions between anterior and posterior (A-P) connectivity. Here, we examined the functional connectivity (FC) differences between young and older adults at high-resolution within the medial temporal lobe network (entorhinal, perirhinal, and parahippocampal cortices), allowing us to explore how hippocampal subfield connectivity across the longitudinal axis of the hippocampus changes with age. Overall, we found reliably greater connectivity for younger adults than older adults between the hippocampus and parahippocampal cortex (PHC) and perirhinal cortex (PRC). This drop in functional connectivity was more pronounced in the anterior regions of the hippocampus than the posterior ones, consistent for each of the hippocampal subfields. Further, intra-hippocampal connectivity also reflected an age-related decrease in functional connectivity within the anterior hippocampus in older adults that was offset by an increase in posterior hippocampal functional connectivity. Interestingly, the anterior-posterior dysfunction in older adults between hippocampus and PHC was predictive of lure discrimination performance on the Mnemonic similarity task (MST), suggesting a role in memory performance. While age-related dysfunction within the hippocampal subfields has been well-documented, these results suggest that the age-related dysfunction in hippocampal connectivity across the longitudinal axis may also contribute significantly to memory decline in older adults.
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Affiliation(s)
- Shauna M. Stark
- Department of Neurobiology and Behavior, University of California Irvine
| | - Amy Frithsen
- Department of Neurobiology and Behavior, University of California Irvine
| | - Craig E.L. Stark
- Department of Neurobiology and Behavior, University of California Irvine
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22
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Lee M, Mueller A, Moore T. Differences in Noradrenaline Receptor Expression Across Different Neuronal Subtypes in Macaque Frontal Eye Field. Front Neuroanat 2020; 14:574130. [PMID: 33328901 PMCID: PMC7732642 DOI: 10.3389/fnana.2020.574130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 10/16/2020] [Indexed: 11/14/2022] Open
Abstract
Cognitive functions such as attention and working memory are modulated by noradrenaline receptors in the prefrontal cortex (PFC). The frontal eye field (FEF) has been shown to play an important role in visual spatial attention. However, little is known about the underlying circuitry. The aim of this study was to characterize the expression of noradrenaline receptors on different pyramidal neuron and inhibitory interneuron subtypes in macaque FEF. Using immunofluorescence, we found broad expression of noradrenaline receptors across all layers of the FEF. Differences in the expression of different noradrenaline receptors were observed across different inhibitory interneuron subtypes. No significant differences were observed in the expression of noradrenaline receptors across different pyramidal neuron subtypes. However, we found that putative long-range projecting pyramidal neurons expressed all noradrenaline receptor subtypes at a much higher proportion than any of the other neuronal subtypes. Nearly all long-range projecting pyramidal neurons expressed all types of noradrenaline receptor, suggesting that there is no receptor-specific machinery acting on these long-range projecting pyramidal neurons. This pattern of expression among long-range projecting pyramidal neurons suggests a mechanism by which noradrenergic modulation of FEF activity influences attention and working memory.
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Affiliation(s)
- Max Lee
- Department of Neurobiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, United States
| | - Adrienne Mueller
- Department of Neurobiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, United States
| | - Tirin Moore
- Department of Neurobiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, United States
- Department of Neurobiology, Stanford University, Stanford, CA, United States
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23
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Gray DT, De La Peña NM, Umapathy L, Burke SN, Engle JR, Trouard TP, Barnes CA. Auditory and Visual System White Matter Is Differentially Impacted by Normative Aging in Macaques. J Neurosci 2020; 40:8913-8923. [PMID: 33051354 PMCID: PMC7659446 DOI: 10.1523/jneurosci.1163-20.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 08/06/2020] [Accepted: 10/04/2020] [Indexed: 11/21/2022] Open
Abstract
Deficits in auditory and visual processing are commonly encountered by older individuals. In addition to the relatively well described age-associated pathologies that reduce sensory processing at the level of the cochlea and eye, multiple changes occur along the ascending auditory and visual pathways that further reduce sensory function in each domain. One fundamental question that remains to be directly addressed is whether the structure and function of the central auditory and visual systems follow similar trajectories across the lifespan or sustain the impacts of brain aging independently. The present study used diffusion magnetic resonance imaging and electrophysiological assessments of auditory and visual system function in adult and aged macaques to better understand how age-related changes in white matter connectivity at multiple levels of each sensory system might impact auditory and visual function. In particular, the fractional anisotropy (FA) of auditory and visual system thalamocortical and interhemispheric corticocortical connections was estimated using probabilistic tractography analyses. Sensory processing and sensory system FA were both reduced in older animals compared with younger adults. Corticocortical FA was significantly reduced only in white matter of the auditory system of aged monkeys, while thalamocortical FA was lower only in visual system white matter of the same animals. Importantly, these structural alterations were significantly associated with sensory function within each domain. Together, these results indicate that age-associated deficits in auditory and visual processing emerge in part from microstructural alterations to specific sensory white matter tracts, and not from general differences in white matter condition across the aging brain.SIGNIFICANCE STATEMENT Age-associated deficits in sensory processing arise from structural and functional alterations to both peripheral sensory organs and central brain regions. It remains unclear whether different sensory systems undergo similar or distinct trajectories in function across the lifespan. To provide novel insights into this question, this study combines electrophysiological assessments of auditory and visual function with diffusion MRI in aged macaques. The results suggest that age-related sensory processing deficits in part result from factors that impact the condition of specific white matter tracts, and not from general decreases in connectivity between sensory brain regions. Such anatomic specificity argues for a framework aimed at understanding vulnerabilities with relatively local influence and brain region specificity.
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Affiliation(s)
- Daniel T Gray
- Division of Neural System, Memory and Aging, University of Arizona, Tucson, Arizona 85724
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, Arizona 85724
| | - Nicole M De La Peña
- Division of Neural System, Memory and Aging, University of Arizona, Tucson, Arizona 85724
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, Arizona 85724
| | - Lavanya Umapathy
- Electrical and Computer Engineering, University of Arizona, Tucson, Arizona 85724
| | - Sara N Burke
- Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, Florida 32609
| | - James R Engle
- Division of Neural System, Memory and Aging, University of Arizona, Tucson, Arizona 85724
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, Arizona 85724
| | - Theodore P Trouard
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, Arizona 85724
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona 85724
| | - Carol A Barnes
- Division of Neural System, Memory and Aging, University of Arizona, Tucson, Arizona 85724
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, Arizona 85724
- Departments of Psychology, Neurology and Neuroscience, University of Arizona, Tucson, Arizona 85724
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24
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Severin D, Gallagher M, Kirkwood A. Afterhyperpolarization amplitude in CA1 pyramidal cells of aged Long-Evans rats characterized for individual differences. Neurobiol Aging 2020; 96:43-48. [PMID: 32932137 DOI: 10.1016/j.neurobiolaging.2020.07.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 07/06/2020] [Accepted: 07/25/2020] [Indexed: 11/18/2022]
Abstract
Altered neural excitability is considered a prominent contributing factor to cognitive decline during aging. A clear example is the excess neural activity observed in several temporal lobe structures of cognitively impaired older individuals in rodents and humans. At a cellular level, aging-related changes in mechanisms regulating intrinsic excitability have been well examined in pyramidal cells of the CA1 hippocampal subfield. Studies in the inbred Fisher 344 rat strain document an age-related increase in the slow afterhyperpolarization (AHP) that normally occurs after a burst of action potentials, and serves to reduce subsequent firing. We evaluated the status of the AHP in the outbred Long-Evans rat, a well-established model for studying individual differences in neurocognitive aging. In contrast to the findings reported in the Fisher 344 rats, in the Long-Evan rats we detected a selective reduction in AHP in cognitively impaired aged individuals. We discuss plausible scenarios to account for these differences and also discuss possible implications of these differences.
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Affiliation(s)
- Daniel Severin
- Department of Neurosciences, Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - Alfredo Kirkwood
- Department of Neurosciences, Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, USA.
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25
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Prevention of age-associated neuronal hyperexcitability with improved learning and attention upon knockout or antagonism of LPAR2. Cell Mol Life Sci 2020; 78:1029-1050. [PMID: 32468095 PMCID: PMC7897625 DOI: 10.1007/s00018-020-03553-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 04/16/2020] [Accepted: 05/13/2020] [Indexed: 12/20/2022]
Abstract
Recent studies suggest that synaptic lysophosphatidic acids (LPAs) augment glutamate-dependent cortical excitability and sensory information processing in mice and humans via presynaptic LPAR2 activation. Here, we studied the consequences of LPAR2 deletion or antagonism on various aspects of cognition using a set of behavioral and electrophysiological analyses. Hippocampal neuronal network activity was decreased in middle-aged LPAR2−/− mice, whereas hippocampal long-term potentiation (LTP) was increased suggesting cognitive advantages of LPAR2−/− mice. In line with the lower excitability, RNAseq studies revealed reduced transcription of neuronal activity markers in the dentate gyrus of the hippocampus in naïve LPAR2−/− mice, including ARC, FOS, FOSB, NR4A, NPAS4 and EGR2. LPAR2−/− mice behaved similarly to wild-type controls in maze tests of spatial or social learning and memory but showed faster and accurate responses in a 5-choice serial reaction touchscreen task requiring high attention and fast spatial discrimination. In IntelliCage learning experiments, LPAR2−/− were less active during daytime but normally active at night, and showed higher accuracy and attention to LED cues during active times. Overall, they maintained equal or superior licking success with fewer trials. Pharmacological block of the LPAR2 receptor recapitulated the LPAR2−/− phenotype, which was characterized by economic corner usage, stronger daytime resting behavior and higher proportions of correct trials. We conclude that LPAR2 stabilizes neuronal network excitability upon aging and allows for more efficient use of resting periods, better memory consolidation and better performance in tasks requiring high selective attention. Therapeutic LPAR2 antagonism may alleviate aging-associated cognitive dysfunctions.
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26
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Gray DT, Umapathy L, De La Peña NM, Burke SN, Engle JR, Trouard TP, Barnes CA. Auditory Processing Deficits Are Selectively Associated with Medial Temporal Lobe Mnemonic Function and White Matter Integrity in Aging Macaques. Cereb Cortex 2020; 30:2789-2803. [PMID: 31833551 DOI: 10.1093/cercor/bhz275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Indexed: 12/22/2022] Open
Abstract
Deficits in auditory function and cognition are hallmarks of normative aging. Recent evidence suggests that hearing-impaired individuals have greater risks of developing cognitive impairment and dementia compared to people with intact auditory function, although the neurobiological bases underlying these associations are poorly understood. Here, a colony of aging macaques completed a battery of behavioral tests designed to probe frontal and temporal lobe-dependent cognition. Auditory brainstem responses (ABRs) and visual evoked potentials were measured to assess auditory and visual system function. Structural and diffusion magnetic resonance imaging were then performed to evaluate the microstructural condition of multiple white matter tracts associated with cognition. Animals showing higher cognitive function had significantly better auditory processing capacities, and these associations were selectively observed with tasks that primarily depend on temporal lobe brain structures. Tractography analyses revealed that the fractional anisotropy (FA) of the fimbria-fornix and hippocampal commissure were associated with temporal lobe-dependent visual discrimination performance and auditory sensory function. Conversely, FA of frontal cortex-associated white matter was not associated with auditory processing. Visual sensory function was not associated with frontal or temporal lobe FA, nor with behavior. This study demonstrates significant and selective relationships between ABRs, white matter connectivity, and higher-order cognitive ability.
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Affiliation(s)
- Daniel T Gray
- Division of Neural System, Memory and Aging.,Evelyn F. McKnight Brain Institute
| | - Lavanya Umapathy
- Electrical and Computer Engineering, University of Arizona, Tucson, AZ 85721, USA
| | - Nicole M De La Peña
- Division of Neural System, Memory and Aging.,Evelyn F. McKnight Brain Institute
| | - Sara N Burke
- Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL 32611, USA
| | - James R Engle
- Division of Neural System, Memory and Aging.,Evelyn F. McKnight Brain Institute
| | - Theodore P Trouard
- Evelyn F. McKnight Brain Institute.,Department of Biomedical Engineering
| | - Carol A Barnes
- Division of Neural System, Memory and Aging.,Evelyn F. McKnight Brain Institute.,Departments of Psychology, Neurology and Neuroscience, University of Arizona, Tucson, AZ 85721, USA
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27
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Gwilt M, Bauer M, Bast T. Frequency- and state-dependent effects of hippocampal neural disinhibition on hippocampal local field potential oscillations in anesthetized rats. Hippocampus 2020; 30:1021-1043. [PMID: 32396678 DOI: 10.1002/hipo.23212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/09/2020] [Accepted: 04/09/2020] [Indexed: 11/11/2022]
Abstract
Reduced inhibitory GABA function, so-called neural disinhibition, has been implicated in cognitive disorders, including schizophrenia and age-related cognitive decline. We previously showed in rats that hippocampal disinhibition by local microinfusion of the GABA-A receptor antagonist picrotoxin disrupted memory and attention and enhanced hippocampal multi-unit burst firing recorded around the infusion site under isoflurane anesthesia. Here, we analyzed the hippocampal local field potential (LFP) recorded alongside the multi-unit data. We predicted frequency-specific LFP changes, based on previous studies implicating GABA in hippocampal oscillations, with the weight of evidence suggesting that disinhibition would facilitate theta and disrupt gamma oscillations. Using a new semi-automated method based on the kurtosis of the LFP peak-amplitude distribution as well as on amplitude envelope thresholding, we separated three distinct hippocampal LFP states under isoflurane anesthesia: "burst" and "suppression" states-high-amplitude LFP spike bursts and the interspersed low-amplitudeperiods-and a medium-amplitude "continuous" state. The burst state showed greater overall power than suppression and continuous states and higher relative delta/theta power, but lower relative beta/gamma power. The burst state also showed reduced functional connectivity across the hippocampal recording area, especially around theta and beta frequencies. Overall neuronal firing was higher in the burst than the other two states, whereas the proportion of burst firing was higher in burst and continuous states than the suppression state. Disinhibition caused state- and frequency-dependent LFP changes, tending to increase power at lower frequencies (<20 Hz), but to decrease power and connectivity at higher frequencies (>20 Hz) in burst and suppression states. The disinhibition-induced enhancement of multi-unit bursting was also state-dependent, tending to be more pronounced in burst and suppression states than the continuous state. Overall, we characterized three distinct hippocampal LFP states in isoflurane-anesthetized rats. Disinhibition changed hippocampal LFP oscillations in a state- and frequency-dependent way. Moreover, the disinhibition-induced enhancement of multi-unit bursting was also LFP state-dependent.
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Affiliation(s)
- Miriam Gwilt
- School of Psychology and Neuroscience@Nottingham, University of Nottingham, Nottingham, UK
| | - Markus Bauer
- School of Psychology and Neuroscience@Nottingham, University of Nottingham, Nottingham, UK
| | - Tobias Bast
- School of Psychology and Neuroscience@Nottingham, University of Nottingham, Nottingham, UK
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28
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Liang X, Hsu LM, Lu H, Ash JA, Rapp PR, Yang Y. Functional Connectivity of Hippocampal CA3 Predicts Neurocognitive Aging via CA1-Frontal Circuit. Cereb Cortex 2020; 30:4297-4305. [PMID: 32239141 DOI: 10.1093/cercor/bhaa008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/08/2019] [Accepted: 01/08/2020] [Indexed: 01/06/2023] Open
Abstract
The CA3 and CA1 principal cell fields of the hippocampus are vulnerable to aging, and age-related dysfunction in CA3 may be an early seed event closely linked to individual differences in memory decline. However, whether the differential vulnerability of CA3 and CA1 is associated with broader disruption in network-level functional interactions in relation to age-related memory impairment, and more specifically, whether CA3 dysconnectivity contributes to the effects of aging via CA1 network connectivity, has been difficult to test. Here, using resting-state fMRI in a group of aged rats uncontaminated by neurodegenerative disease, aged rats displayed widespread reductions in functional connectivity of CA3 and CA1 fields. Age-related memory deficits were predicted by connectivity between left CA3 and hippocampal circuitry along with connectivity between left CA1 and infralimbic prefrontal cortex. Notably, the effects of CA3 connectivity on memory performance were mediated by CA1 connectivity with prefrontal cortex. We additionally found that spatial learning and memory were associated with functional connectivity changes lateralized to the left CA3 and CA1 divisions. These results provide novel evidence that network-level dysfunction involving interactions of CA3 with CA1 is an early marker of poor cognitive outcome in aging.
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Affiliation(s)
- Xia Liang
- Laboratory for Space Environment and Physical Sciences, Harbin Institute of Technology, Harbin 150001, China.,Neuroimaging Research Branch, National Institute on Drug Abuse, Biomedical Research Center, National Institutes of Health (NIH), Baltimore, MD 21224, USA
| | - Li-Ming Hsu
- Neuroimaging Research Branch, National Institute on Drug Abuse, Biomedical Research Center, National Institutes of Health (NIH), Baltimore, MD 21224, USA.,Department of Radiology and Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Hanbing Lu
- Neuroimaging Research Branch, National Institute on Drug Abuse, Biomedical Research Center, National Institutes of Health (NIH), Baltimore, MD 21224, USA
| | - Jessica A Ash
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Biomedical Research Center, NIH, Baltimore, MD 21224, USA
| | - Peter R Rapp
- Laboratory of Behavioral Neuroscience, National Institute on Aging, Biomedical Research Center, NIH, Baltimore, MD 21224, USA
| | - Yihong Yang
- Neuroimaging Research Branch, National Institute on Drug Abuse, Biomedical Research Center, National Institutes of Health (NIH), Baltimore, MD 21224, USA
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29
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Zhang L, Qin Z, Ricke KM, Cruz SA, Stewart AFR, Chen HH. Hyperactivated PTP1B phosphatase in parvalbumin neurons alters anterior cingulate inhibitory circuits and induces autism-like behaviors. Nat Commun 2020; 11:1017. [PMID: 32094367 PMCID: PMC7039907 DOI: 10.1038/s41467-020-14813-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 02/05/2020] [Indexed: 01/05/2023] Open
Abstract
Individuals with autism spectrum disorder (ASD) have social interaction deficits and difficulty filtering information. Inhibitory interneurons filter information at pyramidal neurons of the anterior cingulate cortex (ACC), an integration hub for higher-order thalamic inputs important for social interaction. Humans with deletions including LMO4, an endogenous inhibitor of PTP1B, display intellectual disabilities and occasionally autism. PV-Lmo4KO mice ablate Lmo4 in PV interneurons and display ASD-like repetitive behaviors and social interaction deficits. Surprisingly, increased PV neuron-mediated peri-somatic feedforward inhibition to the pyramidal neurons causes a compensatory reduction in (somatostatin neuron-mediated) dendritic inhibition. These homeostatic changes increase filtering of mediodorsal-thalamocortical inputs but reduce filtering of cortico-cortical inputs and narrow the range of stimuli ACC pyramidal neurons can distinguish. Simultaneous ablation of PTP1B in PV-Lmo4KO neurons prevents these deficits, indicating that PTP1B activation in PV interneurons contributes to ASD-like characteristics and homeostatic maladaptation of inhibitory circuits may contribute to deficient information filtering in ASD.
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Affiliation(s)
- Li Zhang
- Ottawa Hospital Research Institute, Neuroscience, Ottawa, Canada. .,University of Ottawa Brain and Mind Institute, Ottawa, Canada.
| | - Zhaohong Qin
- Ottawa Hospital Research Institute, Neuroscience, Ottawa, Canada.,University of Ottawa Brain and Mind Institute, Ottawa, Canada
| | - Konrad M Ricke
- Ottawa Hospital Research Institute, Neuroscience, Ottawa, Canada.,University of Ottawa Brain and Mind Institute, Ottawa, Canada.,University of Ottawa Heart Institute, Ottawa, Canada.,Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Shelly A Cruz
- Ottawa Hospital Research Institute, Neuroscience, Ottawa, Canada.,University of Ottawa Brain and Mind Institute, Ottawa, Canada
| | - Alexandre F R Stewart
- University of Ottawa Heart Institute, Ottawa, Canada. .,Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada. .,Centre for Infection, Immunity and Inflammation, University of Ottawa, Ottawa, Canada.
| | - Hsiao-Huei Chen
- Ottawa Hospital Research Institute, Neuroscience, Ottawa, Canada. .,University of Ottawa Brain and Mind Institute, Ottawa, Canada. .,Centre for Infection, Immunity and Inflammation, University of Ottawa, Ottawa, Canada. .,Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada. .,Medicine, University of Ottawa, Ottawa, Canada.
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30
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Gray DT, Barnes CA. Experiments in macaque monkeys provide critical insights into age-associated changes in cognitive and sensory function. Proc Natl Acad Sci U S A 2019; 116:26247-26254. [PMID: 31871147 PMCID: PMC6936691 DOI: 10.1073/pnas.1902279116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The use of animal models in brain aging research has led to numerous fundamental insights into the neurobiological processes that underlie changes in brain function associated with normative aging. Macaque monkeys have become the predominant nonhuman primate model system in brain aging research due to their striking similarities to humans in their behavioral capacities, sensory processing abilities, and brain architecture. Recent public concern about nonhuman primate research has made it imperative to attempt to clearly articulate the potential benefits to human health that this model enables. The present review will highlight how nonhuman primates provide a critical bridge between experiments conducted in rodents and development of therapeutics for humans. Several studies discussed here exemplify how nonhuman primate research has enriched our understanding of cognitive and sensory decline in the aging brain, as well as how this work has been important for translating mechanistic implications derived from experiments conducted in rodents to human brain aging research.
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Affiliation(s)
- Daniel T. Gray
- Division of Neural System, Memory & Aging, The University of Arizona, Tucson, AZ 85724
- Evelyn F. McKnight Brain Institute, The University of Arizona, Tucson, AZ 85724
| | - Carol A. Barnes
- Division of Neural System, Memory & Aging, The University of Arizona, Tucson, AZ 85724
- Evelyn F. McKnight Brain Institute, The University of Arizona, Tucson, AZ 85724
- Department of Psychology, The University of Arizona, Tucson, AZ 85724
- Department of Neurology, The University of Arizona, Tucson, AZ 85724
- Department of Neuroscience, The University of Arizona, Tucson, AZ 85724
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31
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Long JM, Perez EJ, Roberts JA, Roberts MT, Rapp PR. Reelin in the Years: decline in the number of reelin immunoreactive neurons in layer II of the entorhinal cortex in aged monkeys with memory impairment. Neurobiol Aging 2019; 87:132-137. [PMID: 31952867 DOI: 10.1016/j.neurobiolaging.2019.12.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 12/12/2019] [Accepted: 12/12/2019] [Indexed: 01/17/2023]
Abstract
The glycoprotein reelin has been implicated in both memory-related synaptic plasticity and Alzheimer's disease pathogenesis. Aged rats with memory impairment display decreased reelin expression in layer II of the entorhinal cortex (EC) relative to memory-intact subjects, and here we tested whether this effect extends to the primate brain. Seven young adult (8-10 years) and 14 aged (27-38 years) rhesus monkeys (Macaca mulatta) were examined, including 7 old animals classified as impaired based on their scores from a delayed nonmatching-to-sample recognition memory test. Histological sections spanning the rostrocaudal extent of the intermediate and caudal divisions of EC were processed by immunohistochemistry and the total number of reelin-positive neurons in layer II was estimated using design-based stereological techniques. The main finding was that the number of reelin-expressing neurons in EC layer II is decreased selectively in aged monkeys with memory deficits relative to young adult and aged subjects with intact memory. The results add to evidence implicating EC-hippocampal integrity in neurocognitive aging, and they suggest that disrupted reelin signaling may be among the mechanisms that mediate the associated vulnerability of this circuitry in Alzheimer's disease.
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Affiliation(s)
- Jeffrey M Long
- Neurocognitive Aging Section, Laboratory of Behavioral Neuroscience, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Evelyn J Perez
- Neurocognitive Aging Section, Laboratory of Behavioral Neuroscience, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | | | - Mary T Roberts
- California National Primate Research Center, Davis, CA, USA
| | - Peter R Rapp
- Neurocognitive Aging Section, Laboratory of Behavioral Neuroscience, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
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32
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Zhu B, Eom J, Hunt RF. Transplanted interneurons improve memory precision after traumatic brain injury. Nat Commun 2019; 10:5156. [PMID: 31727894 PMCID: PMC6856380 DOI: 10.1038/s41467-019-13170-w] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/23/2019] [Indexed: 12/26/2022] Open
Abstract
Repair of the traumatically injured brain has been envisioned for decades, but regenerating new neurons at the site of brain injury has been challenging. We show GABAergic progenitors, derived from the embryonic medial ganglionic eminence, migrate long distances following transplantation into the hippocampus of adult mice with traumatic brain injury, functionally integrate as mature inhibitory interneurons and restore post-traumatic decreases in synaptic inhibition. Grafted animals had improvements in memory precision that were reversed by chemogenetic silencing of the transplanted neurons and a long-lasting reduction in spontaneous seizures. Our results reveal a striking ability of transplanted interneurons for incorporating into injured brain circuits, and this approach is a powerful therapeutic strategy for correcting post-traumatic memory and seizure disorders.
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Affiliation(s)
- Bingyao Zhu
- Department of Anatomy & Neurobiology, University of California, Irvine, CA, 92697, USA
| | - Jisu Eom
- Department of Anatomy & Neurobiology, University of California, Irvine, CA, 92697, USA
| | - Robert F Hunt
- Department of Anatomy & Neurobiology, University of California, Irvine, CA, 92697, USA. .,Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA, 92697, USA. .,Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, CA, 92697, USA.
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33
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Stern Y, Barnes CA, Grady C, Jones RN, Raz N. Brain reserve, cognitive reserve, compensation, and maintenance: operationalization, validity, and mechanisms of cognitive resilience. Neurobiol Aging 2019; 83:124-129. [PMID: 31732015 PMCID: PMC6859943 DOI: 10.1016/j.neurobiolaging.2019.03.022] [Citation(s) in RCA: 216] [Impact Index Per Article: 43.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 03/05/2019] [Accepted: 03/11/2019] [Indexed: 01/22/2023]
Abstract
Significant individual differences in the trajectories of cognitive aging and in age-related changes of brain structure and function have been reported in the past half-century. In some individuals, significant pathological changes in the brain are observed in conjunction with relatively well-preserved cognitive performance. Multiple constructs have been invoked to explain this paradox of resilience, including brain reserve, cognitive reserve, brain maintenance, and compensation. The aim of this session of the Cognitive Aging Summit III was to examine the overlap and distinctions in definitions and measurement of these constructs, to discuss their neural and behavioral correlates and to propose plausible mechanisms of individual cognitive resilience in the face of typical age-related neural declines.
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Affiliation(s)
- Yaakov Stern
- Cognitive Neuroscience Division, Department of Neurology, Columbia University, New York, NY, USA
| | - Carol A Barnes
- Departments of Psychology, Neurology and Neuroscience, and Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA
| | - Cheryl Grady
- Rotman Research Institute, Baycrest Centre, and Departments of Psychology and Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Richard N Jones
- Departments of Neurology and Psychiatry & Human Behavior, Brown University, Providence, RI, USA
| | - Naftali Raz
- Institute of Gerontology and Department of Psychology, Wayne State University, Detroit, MI, USA; Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.
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34
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Yao LH, Wang J, Liu C, Wei S, Li G, Wang S, Meng W, Liu ZB, Huang LP. Cordycepin protects against β-amyloid and ibotenic acid-induced hippocampal CA1 pyramidal neuronal hyperactivity. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2019; 23:483-491. [PMID: 31680770 PMCID: PMC6819905 DOI: 10.4196/kjpp.2019.23.6.483] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/29/2019] [Accepted: 08/12/2019] [Indexed: 12/13/2022]
Abstract
Cordycepin exerts neuroprotective effects against excitotoxic neuronal death. However, its direct electrophysiological evidence in Alzheimer's disease (AD) remains unclear. This study aimed to explore the electrophysiological mechanisms underlying the protective effect of cordycepin against the excitotoxic neuronal insult in AD using whole-cell patch clamp techniques. β-Amyloid (Aβ) and ibotenic acid (IBO)-induced injury model in cultured hippocampal neurons was used for the purpose. The results revealed that cordycepin significantly delayed Aβ + IBO-induced excessive neuronal membrane depolarization. It increased the onset time/latency, extended the duration, and reduced the slope in both slow and rapid depolarization. Additionally, cordycepin reversed the neuronal hyperactivity in Aβ + IBO-induced evoked action potential (AP) firing, including increase in repetitive firing frequency, shortening of evoked AP latency, decrease in the amplitude of fast afterhyperpolarization, and increase in membrane depolarization. Further, the suppressive effect of cordycepin against Aβ + IBO-induced excessive neuronal membrane depolarization and neuronal hyperactivity was blocked by DPCPX (8-cyclopentyl-1,3-dipropylxanthine, an adenosine A1 receptor-specific blocker). Collectively, these results revealed the suppressive effect of cordycepin against the Aβ + IBO-induced excitotoxic neuronal insult by attenuating excessive neuronal activity and membrane depolarization, and the mechanism through the activation of A1R is strongly recommended, thus highlighting the therapeutic potential of cordycepin in AD.
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Affiliation(s)
- Li-Hua Yao
- School of Life Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China.,School of Sport Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Jinxiu Wang
- School of Life Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Chao Liu
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi 330004, PR China
| | - Shanshan Wei
- School of Life Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Guoyin Li
- School of Sport Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Songhua Wang
- School of Life Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Wei Meng
- School of Life Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Zhi-Bin Liu
- School of Sport Science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi 330013, PR China
| | - Li-Ping Huang
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi 330004, PR China
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35
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Hernandez AR, Hernandez CM, Truckenbrod LM, Campos KT, McQuail JA, Bizon JL, Burke SN. Age and Ketogenic Diet Have Dissociable Effects on Synapse-Related Gene Expression Between Hippocampal Subregions. Front Aging Neurosci 2019; 11:239. [PMID: 31607897 PMCID: PMC6755342 DOI: 10.3389/fnagi.2019.00239] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 08/19/2019] [Indexed: 01/01/2023] Open
Abstract
As the number of individuals living beyond the age of 65 is rapidly increasing, so is the need to develop strategies to combat the age-related cognitive decline that may threaten independent living. Although the link between altered neuronal signaling and age-related cognitive impairments is not completely understood, it is evident that declining cognitive abilities are at least partially due to synaptic dysfunction. Aging is accompanied by well-documented changes in both excitatory and inhibitory synaptic signaling across species. Age-related synaptic alterations are not uniform across the brain, however, with different regions showing unique patterns of vulnerability in advanced age. In the hippocampus, increased activity within the CA3 subregion has been observed across species, and this can be reversed with anti-epileptic medication. In contrast to CA3, the dentate gyrus shows reduced activity with age and declining metabolic activity. Ketogenic diets have been shown to decrease seizure incidence and severity in epilepsy, improve metabolic function in diabetes type II, and improve cognitive function in aged rats. This link between neuronal activity and metabolism suggests that metabolic interventions may be able to ameliorate synaptic signaling deficits accompanying advanced age. We therefore investigated the ability of a dietary regimen capable of inducing nutritional ketosis and improving cognition to alter synapse-related gene expression across the dentate gyrus, CA3 and CA1 subregions of the hippocampus. Following 12 weeks of a ketogenic or calorie-matched standard diet, RTq-PCR was used to quantify expression levels of excitatory and inhibitory synaptic signaling genes within CA1, CA3 and dentate gyrus. While there were no age or diet-related changes in CA1 gene expression, expression levels were significantly altered within CA3 by age and within the dentate gyrus by diet for several genes involved in presynaptic glutamate regulation and postsynaptic excitation and plasticity. These data demonstrate subregion-specific alterations in synaptic signaling with age and the potential for a ketogenic diet to alter these processes in dissociable ways across different brain structures that are uniquely vulnerable in older animals.
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Affiliation(s)
- Abbi R. Hernandez
- Department of Neurosciences, University of Florida, Gainesville, FL, United States
| | - Caesar M. Hernandez
- Department of Neurosciences, University of Florida, Gainesville, FL, United States
| | - Leah M. Truckenbrod
- Department of Neurosciences, University of Florida, Gainesville, FL, United States
| | - Keila T. Campos
- Department of Neurosciences, University of Florida, Gainesville, FL, United States
| | - Joseph A. McQuail
- Department of Physiology, Pharmacology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
| | - Jennifer L. Bizon
- Department of Neurosciences, University of Florida, Gainesville, FL, United States
| | - Sara N. Burke
- Department of Neurosciences, University of Florida, Gainesville, FL, United States
- Institute on Aging, University of Florida, Gainesville, FL, United States
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36
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Myrum C, Rossi SL, Perez EJ, Rapp PR. Cortical network dynamics are coupled with cognitive aging in rats. Hippocampus 2019; 29:1165-1177. [PMID: 31334577 DOI: 10.1002/hipo.23130] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 05/23/2019] [Accepted: 06/05/2019] [Indexed: 12/27/2022]
Abstract
Changes in neuronal network activity and increased interindividual variability in memory are among the most consistent features of growing older. Here, we examined the relationship between these hallmarks of aging. Young and aged rats were trained on a water maze task where aged individuals reliably display an increased range of spatial memory capacities relative to young. Two weeks later, neuronal activity was induced pharmacologically with a low dose of pilocarpine and control animals received vehicle. Activity levels were proxied by quantifying the immediate early gene products Arc and c-Fos. While no relationship was observed between basal, resting activity, and individual differences in spatial memory in any brain region, pilocarpine-induced marker expression was tightly coupled with memory in all areas of the prefrontal cortex (PFC) and hippocampus examined. The nature of this association, however, differed across regions and in relation to age-related cognitive outcome. Specifically, in the medial PFC, induced activity was greatest in aged rats with cognitive impairment and correlated with water maze performance across all subjects. In the hippocampus, the range of induced marker expression was comparable between groups and similarly coupled with memory in both impaired and unimpaired aged rats. Together the findings highlight that the dynamic range of neural network activity across multiple brain regions is a critical component of neurocognitive aging.
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Affiliation(s)
- Craig Myrum
- Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, Maryland
| | - Sharyn L Rossi
- Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, Maryland
| | - Evelyn J Perez
- Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, Maryland
| | - Peter R Rapp
- Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, Maryland
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37
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Das SC, Chen D, Callor WB, Christensen E, Coon H, Williams ME. DiI-mediated analysis of presynaptic and postsynaptic structures in human postmortem brain tissue. J Comp Neurol 2019; 527:3087-3098. [PMID: 31152449 DOI: 10.1002/cne.24722] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 05/24/2019] [Accepted: 05/24/2019] [Indexed: 12/20/2022]
Abstract
Most cognitive and psychiatric disorders are thought to be disorders of the synapse, yet the precise synapse defects remain unknown. Because synapses are highly specialized anatomical structures, defects in synapse formation and function can often be observed as changes in microscale neuroanatomy. Unfortunately, few methods are available for accurate analysis of synaptic structures in human postmortem tissues. Here, we present a methodological pipeline for assessing presynaptic and postsynaptic structures in human postmortem tissue that is accurate, rapid, and relatively inexpensive. Our method uses small tissue blocks from postmortem human brains, immersion fixation, lipophilic dye (DiI) labeling, and confocal microscopy. As proof of principle, we analyzed presynaptic and postsynaptic structures from hippocampi of 13 individuals aged 4 months to 71 years. Our results indicate that postsynaptic CA1 dendritic spine shape and density do not change in adults, while presynaptic DG mossy fiber boutons undergo significant structural rearrangements with normal aging. This suggests that mossy fiber synapses, which play a major role in learning and memory, may remain dynamic throughout life. Importantly, we find that human CA1 spine densities observed using this method on tissue that is up to 28 h postmortem is comparable to prior studies using tissue with much shorter postmortem intervals. Thus, the ease of our protocol and suitability on tissue with longer postmortem intervals should facilitate higher-powered studies of human presynaptic and postsynaptic structures in healthy and diseased states.
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Affiliation(s)
- Sujan C Das
- Department of Psychiatry, University of Utah School of Medicine, Salt Lake City, Utah
| | - Danli Chen
- Department of Psychiatry, University of Utah School of Medicine, Salt Lake City, Utah
| | | | - Eric Christensen
- Utah State Office of Medical Examiner, Utah Department of Health, Salt Lake City, Utah
| | - Hilary Coon
- Department of Psychiatry, University of Utah School of Medicine, Salt Lake City, Utah
| | - Megan E Williams
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah
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38
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Kyle CT, Stokes J, Bennett J, Meltzer J, Permenter MR, Vogt JA, Ekstrom A, Barnes CA. Cytoarchitectonically-driven MRI atlas of nonhuman primate hippocampus: Preservation of subfield volumes in aging. Hippocampus 2019; 29:409-421. [PMID: 29072793 PMCID: PMC5920786 DOI: 10.1002/hipo.22809] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 09/29/2017] [Accepted: 10/24/2017] [Indexed: 11/12/2022]
Abstract
Identification of primate hippocampal subfields in vivo using structural MRI imaging relies on variable anatomical guidelines, signal intensity differences, and heuristics to differentiate between regions (Yushkevich et al., 2015a). Thus, a clear anatomically-driven basis for subfield demarcation is lacking. Recent work, however, has begun to develop methods to use ex vivo histology or ex vivo MRI (Adler et al., 2014; Iglesias et al., 2015) that have the potential to inform subfield demarcations of in vivo images. For optimal results, however, ex vivo and in vivo images should ideally be matched within the same healthy brains, with the goal to develop a neuroanatomically-driven basis for in vivo structural MRI images. Here, we address this issue in young and aging rhesus macaques (young n = 5 and old n = 5) using ex vivo Nissl-stained sections in which we identified the dentate gyrus, CA3, CA2, CA1, subiculum, presubiculum, and parasubiculum guided by morphological cell properties (30 μm thick sections spaced at 240 μm intervals and imaged at 161 nm/pixel). The histologically identified boundaries were merged with in vivo structural MRIs (0.625 × 0.625 × 1 mm) from the same subjects via iterative rigid and diffeomorphic registration resulting in probabilistic atlases of young and old rhesus macaques. Our results indicate stability in hippocampal subfield volumes over an age range of 13 to 32 years, consistent with previous results showing preserved whole hippocampal volume in aged macaques (Shamy et al., 2006). Together, our methods provide a novel approach for identifying hippocampal subfields in non-human primates and a potential 'ground truth' for more accurate identification of hippocampal subfield boundaries on in vivo MRIs. This could, in turn, have applications in humans where accurately identifying hippocampal subfields in vivo is a critical research goal.
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Affiliation(s)
- Colin T Kyle
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ
| | - Jared Stokes
- Department of Psychology, University of California, Davis, CA
| | - Jeffrey Bennett
- Department of Psychiatry and Behavioral Science and M.I.N.D. Institute, UC Davis, Sacramento, CA
| | - Jeri Meltzer
- California National Primate Research Center, University of California, Davis, Davis, CA
| | - Michele R Permenter
- California National Primate Research Center, University of California, Davis, Davis, CA
| | - Julie A Vogt
- California National Primate Research Center, University of California, Davis, Davis, CA
| | - Arne Ekstrom
- Department of Psychology, University of California, Davis, CA
- Center for Neuroscience, University of California, Davis, CA
| | - Carol A Barnes
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ
- Division of Neural Systems, Memory and Aging, University of Arizona, Tucson, AZ
- Departments of Psychology, Neurology and Neuroscience, University of Arizona, Tucson, AZ
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39
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Alteration of parvalbumin expression and perineuronal nets formation in the cerebral cortex of aged mice. Mol Cell Neurosci 2019; 95:31-42. [DOI: 10.1016/j.mcn.2018.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 12/18/2018] [Accepted: 12/26/2018] [Indexed: 01/15/2023] Open
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40
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Diersch N, Wolbers T. The potential of virtual reality for spatial navigation research across the adult lifespan. ACTA ACUST UNITED AC 2019; 222:222/Suppl_1/jeb187252. [PMID: 30728232 DOI: 10.1242/jeb.187252] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Older adults often experience serious problems in spatial navigation, and alterations in underlying brain structures are among the first indicators for a progression to neurodegenerative diseases. Studies investigating the neural mechanisms of spatial navigation and its changes across the adult lifespan are increasingly using virtual reality (VR) paradigms. VR offers major benefits in terms of ecological validity, experimental control and options to track behavioral responses. However, navigation in the real world differs from navigation in VR in several aspects. In addition, the importance of body-based or visual cues for navigation varies between animal species. Incongruences between sensory and motor input in VR might consequently affect their performance to a different degree. After discussing the specifics of using VR in spatial navigation research across species, we outline several challenges when investigating age-related deficits in spatial navigation with the help of VR. In addition, we discuss ways to reduce their impact, together with the possibilities VR offers for improving navigational abilities in older adults.
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Affiliation(s)
- Nadine Diersch
- Aging & Cognition Research Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Thomas Wolbers
- Aging & Cognition Research Group, German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany.,Center for Behavioural Brain Sciences (CBBS), Otto-von-Guericke University Magdeburg, 39120 Magdeburg, Germany.,Medical Faculty, University Hospital Magdeburg, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany
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41
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Johnson SA, Turner SM, Lubke KN, Cooper TL, Fertal KE, Bizon JL, Maurer AP, Burke SN. Experience-Dependent Effects of Muscimol-Induced Hippocampal Excitation on Mnemonic Discrimination. Front Syst Neurosci 2019; 12:72. [PMID: 30687032 PMCID: PMC6335355 DOI: 10.3389/fnsys.2018.00072] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Accepted: 12/21/2018] [Indexed: 12/12/2022] Open
Abstract
Memory requires similar episodes with overlapping features to be represented distinctly, a process that is disrupted in many clinical conditions as well as normal aging. Data from humans have linked this ability to activity in hippocampal CA3 and dentate gyrus (DG). While animal models have shown the perirhinal cortex is critical for disambiguating similar stimuli, hippocampal activity has not been causally linked to discrimination abilities. The goal of the current study was to determine how disrupting CA3/DG activity would impact performance on a rodent mnemonic discrimination task. Rats were surgically implanted with bilateral guide cannulae targeting dorsal CA3/DG. In Experiment 1, the effect of intra-hippocampal muscimol on target-lure discrimination was assessed within subjects in randomized blocks. Muscimol initially impaired discrimination across all levels of target-lure similarity, but performance improved on subsequent test blocks irrespective of stimulus similarity and infusion condition. To clarify these results, Experiment 2 examined whether prior experience with objects influenced the effect of muscimol on target-lure discrimination. Rats that received vehicle infusions in a first test block, followed by muscimol in a second block, did not show discrimination impairments for target-lure pairs of any similarity. In contrast, rats that received muscimol infusions in the first test block were impaired across all levels of target-lure similarity. Following discrimination tests, rats from Experiment 2 were trained on a spatial alternation task. Muscimol infusions increased the number of spatial errors made, relative to vehicle infusions, confirming that muscimol remained effective in disrupting behavioral performance. At the conclusion of behavioral experiments, fluorescence in situ hybridization for the immediate-early genes Arc and Homer1a was used to determine the proportion of neurons active following muscimol infusion. Contrary to expectations, muscimol increased neural activity in DG. An additional experiment was carried out to quantify neural activity in naïve rats that received an intra-hippocampal infusion of vehicle or muscimol. Results confirmed that muscimol led to DG excitation, likely through its actions on interneuron populations in hilar and molecular layers of DG and consequent disinhibition of principal cells. Taken together, our results suggest disruption of coordinated neural activity across the hippocampus impairs mnemonic discrimination when lure stimuli are novel.
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Affiliation(s)
- Sarah A Johnson
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Sean M Turner
- Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, United States
| | - Katelyn N Lubke
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Tara L Cooper
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Kaeli E Fertal
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Jennifer L Bizon
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Andrew P Maurer
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States.,Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States
| | - Sara N Burke
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States.,Institute on Aging, University of Florida, Gainesville, FL, United States
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42
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Branch A, Monasterio A, Blair G, Knierim JJ, Gallagher M, Haberman RP. Aged rats with preserved memory dynamically recruit hippocampal inhibition in a local/global cue mismatch environment. Neurobiol Aging 2019; 76:151-161. [PMID: 30716540 DOI: 10.1016/j.neurobiolaging.2018.12.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 12/14/2018] [Accepted: 12/27/2018] [Indexed: 10/27/2022]
Abstract
Similar to elderly humans, aged outbred Long-Evans rats exhibit individual differences in memory abilities, including a subset of aged rats that maintain memory function on par with young adults. Such individuals provide a basis for investigating mechanisms of resilience to age-related decline. The present study examined hippocampal gene expression in young adults and aged rats with preserved memory function under behavioral task conditions well established for assessing information processing central to the formation of episodic memory. Although behavioral measures and hippocampal gene induction associated with neural activity and synaptic plasticity were similar across age groups, a marker for inhibitory interneuron function in the hippocampal formation was distinctively increased only in aged rats but not in young adults. Because heightened hippocampal neural activity is associated with age-related memory impairment across species, including rats, monkeys, and humans, this finding may represent an adaptive homeostatic adjustment necessary to maintain neural plasticity and memory function in aging.
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Affiliation(s)
- Audrey Branch
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - Amy Monasterio
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - Grace Blair
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - James J Knierim
- Department of Neuroscience and Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA
| | - Rebecca P Haberman
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA.
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43
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Burke SN, Foster TC. Animal models of cognitive aging and circuit-specific vulnerability. HANDBOOK OF CLINICAL NEUROLOGY 2019; 167:19-36. [PMID: 31753133 DOI: 10.1016/b978-0-12-804766-8.00002-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Medial temporal lobe and prefrontal cortical structures are particularly vulnerable to dysfunction in advanced age and neurodegenerative diseases. This review focuses on cognitive aging studies in animals to illustrate the important aspects of the animal model paradigm for investigation of age-related memory and executive function loss. Particular attention is paid to the discussion of the face, construct, and predictive validity of animal models for determining the possible mechanisms of regional vulnerability in aging and for identifying novel therapeutic strategies. Aging is associated with a host of regionally specific neurobiologic alterations. Thus, targeted interventions that restore normal activity in one brain region may exacerbate aberrant activity in another, hindering the restoration of function at the behavioral level. As such, interventions that target the optimization of "cognitive networks" rather than discrete brain regions may be more effective for improving functional outcomes in the elderly.
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Affiliation(s)
- Sara N Burke
- Department of Neuroscience, William L. and Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Thomas C Foster
- Department of Neuroscience, William L. and Evelyn F. McKnight Brain Institute, University of Florida, Gainesville, FL, United States.
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44
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Hernandez AR, Hernandez CM, Campos K, Truckenbrod L, Federico Q, Moon B, McQuail JA, Maurer AP, Bizon JL, Burke SN. A Ketogenic Diet Improves Cognition and Has Biochemical Effects in Prefrontal Cortex That Are Dissociable From Hippocampus. Front Aging Neurosci 2018; 10:391. [PMID: 30559660 PMCID: PMC6286979 DOI: 10.3389/fnagi.2018.00391] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 11/08/2018] [Indexed: 12/22/2022] Open
Abstract
Age-related cognitive decline has been linked to a diverse set of neurobiological mechanisms, including bidirectional changes in proteins critical for neuron function. Importantly, these alterations are not uniform across the brain. For example, the hippocampus (HPC) and prefrontal cortex (PFC) show distinct patterns of dysfunction in advanced age. Because higher cognitive functions require large–scale interactions across prefrontal cortical and hippocampal networks, selectively targeting an alteration within one region may not broadly restore function to improve cognition. One mechanism for decline that the PFC and HPC share, however, is a reduced ability to utilize glucose for energy metabolism. Although this suggests that therapeutic strategies bypassing the need for neuronal glycolysis may be beneficial for treating cognitive aging, this approach has not been empirically tested. Thus, the current study used a ketogenic diet (KD) as a global metabolic strategy for improving brain function in young and aged rats. After 12 weeks, rats were trained to perform a spatial alternation task through an asymmetrical maze, in which one arm was closed and the other was open. Both young and aged KD-fed rats showed resilience against the anxiogenic open arm, training to alternation criterion performance faster than control animals. Following alternation testing, rats were trained to perform a cognitive dual task that required working memory while simultaneously performing a bi-conditional association task (WM/BAT), which requires PFC–HPC interactions. All KD-fed rats also demonstrated improved performance on WM/BAT. At the completion of behavioral testing, tissue punches were collected from the PFC for biochemical analysis. KD-fed rats had biochemical alterations within PFC that were dissociable from previous results in the HPC. Specifically, MCT1 and MCT4, which transport ketone bodies, were significantly increased in KD-fed rats compared to controls. GLUT1, which transports glucose across the blood brain barrier, was decreased in KD-fed rats. Contrary to previous observations within the HPC, the vesicular glutamate transporter (VGLUT1) did not change with age or diet within the PFC. The vesicular GABA transporter (VGAT), however, was increased within PFC similar to HPC. These data suggest that KDs could be optimal for enhancing large-scale network function that is critical for higher cognition.
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Affiliation(s)
- Abbi R Hernandez
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Caesar M Hernandez
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Keila Campos
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Leah Truckenbrod
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Quinten Federico
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Brianna Moon
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Joseph A McQuail
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Andrew P Maurer
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Jennifer L Bizon
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Sara N Burke
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States.,Institute on Aging, University of Florida, Gainesville, FL, United States
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45
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Velasco-Estevez M, Mampay M, Boutin H, Chaney A, Warn P, Sharp A, Burgess E, Moeendarbary E, Dev KK, Sheridan GK. Infection Augments Expression of Mechanosensing Piezo1 Channels in Amyloid Plaque-Reactive Astrocytes. Front Aging Neurosci 2018; 10:332. [PMID: 30405400 PMCID: PMC6204357 DOI: 10.3389/fnagi.2018.00332] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 10/01/2018] [Indexed: 01/07/2023] Open
Abstract
A defining pathophysiological hallmark of Alzheimer's disease (AD) is the amyloid plaque; an extracellular deposit of aggregated fibrillar Aβ1-42 peptides. Amyloid plaques are hard, brittle structures scattered throughout the hippocampus and cerebral cortex and are thought to cause hyperphosphorylation of tau, neurofibrillary tangles, and progressive neurodegeneration. Reactive astrocytes and microglia envelop the exterior of amyloid plaques and infiltrate their inner core. Glia are highly mechanosensitive cells and can almost certainly sense the mismatch between the normally soft mechanical environment of the brain and very stiff amyloid plaques via mechanosensing ion channels. Piezo1, a non-selective cation channel, can translate extracellular mechanical forces to intracellular molecular signaling cascades through a process known as mechanotransduction. Here, we utilized an aging transgenic rat model of AD (TgF344-AD) to study expression of mechanosensing Piezo1 ion channels in amyloid plaque-reactive astrocytes. We found that Piezo1 is upregulated with age in the hippocampus and cortex of 18-month old wild-type rats. However, more striking increases in Piezo1 were measured in the hippocampus of TgF344-AD rats compared to age-matched wild-type controls. Interestingly, repeated urinary tract infections with Escherichia coli bacteria, a common comorbidity in elderly people with dementia, caused further elevations in Piezo1 channel expression in the hippocampus and cortex of TgF344-AD rats. Taken together, we report that aging and peripheral infection augment amyloid plaque-induced upregulation of mechanoresponsive ion channels, such as Piezo1, in astrocytes. Further research is required to investigate the role of astrocytic Piezo1 in the Alzheimer's brain, whether modulating channel opening will protect or exacerbate the disease state, and most importantly, if Piezo1 could prove to be a novel drug target for age-related dementia.
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Affiliation(s)
- María Velasco-Estevez
- Neuroimmulology & Neurotherapeutics Laboratory, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
- Drug Development, Department of Physiology, School of Medicine, Trinity College Dublin, Dublin, Ireland
| | - Myrthe Mampay
- Neuroimmulology & Neurotherapeutics Laboratory, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
| | - Hervé Boutin
- Wolfson Molecular Imaging Centre, Faculty of Biology, Medicine and Health and Manchester Academic Health Sciences Centre, The University of Manchester, Manchester, United Kingdom
| | - Aisling Chaney
- Wolfson Molecular Imaging Centre, Faculty of Biology, Medicine and Health and Manchester Academic Health Sciences Centre, The University of Manchester, Manchester, United Kingdom
- Department of Radiology, Stanford University, Stanford, CA, United States
| | - Peter Warn
- Evotec (UK) Ltd., Manchester Science Park, Manchester, United Kingdom
| | - Andrew Sharp
- Evotec (UK) Ltd., Manchester Science Park, Manchester, United Kingdom
| | - Ellie Burgess
- Evotec (UK) Ltd., Manchester Science Park, Manchester, United Kingdom
| | - Emad Moeendarbary
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
- Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Kumlesh K. Dev
- Drug Development, Department of Physiology, School of Medicine, Trinity College Dublin, Dublin, Ireland
| | - Graham K. Sheridan
- Neuroimmulology & Neurotherapeutics Laboratory, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
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Loss of thin spines and small synapses contributes to defective hippocampal function in aged mice. Neurobiol Aging 2018; 71:91-104. [PMID: 30118927 DOI: 10.1016/j.neurobiolaging.2018.07.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 07/07/2018] [Accepted: 07/14/2018] [Indexed: 12/23/2022]
Abstract
Aging is a normal physiological process associated with impairments in cognitive function, including learning and memory. Here, the underlying synaptic mechanisms by which aging leads to the decline of spatial learning and memory function were investigated in 25-month-old aged mice versus 2-month-old young mice. Deficits of spatial learning and memory, as well as selective loss of thin spines, but not mushroom-type spines on apical dendrites of CA1 pyramidal cells were found in aged mice. Specifically, loss of thin spines in aged mice with memory deficits was primarily found on dendritic segments located in the Schaffer pathway, and the density of thin spines significantly correlated with spatial memory performance. The loss of thin spines was evidenced by a decrease in small synapses that express diminutive amounts of postsynaptic density protein-95 and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit GluR1. Furthermore, mushroom-type spines and GluR1-expressed large synapses were not affected in aged mice with impaired memory. Taken together, these data suggest that the selective loss of those highly plastic thin spines with sparse postsynaptic density protein-95 and GluR1 receptors may significantly contribute to cognitive deficits in aged individuals.
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Mohan A, Thalamuthu A, Mather KA, Zhang Y, Catts VS, Weickert CS, Sachdev PS. Differential expression of synaptic and interneuron genes in the aging human prefrontal cortex. Neurobiol Aging 2018; 70:194-202. [PMID: 30031232 DOI: 10.1016/j.neurobiolaging.2018.06.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 05/10/2018] [Accepted: 06/07/2018] [Indexed: 02/06/2023]
Abstract
Altered inhibition-excitation balance is implicated in brain aging. We hypothesized that expression of 14 genes encoding proteins localized to synapses or interneurons would show age-related changes relative to 1 another in postmortem tissue from the prefrontal cortex of 37 individuals (18-78 years) and that synaptic or interneuron markers would be differentially correlated with human brain volumes across aging. The majority of genes examined were differentially expressed with age, most being downregulated. Expression of 3 interneuron-related genes was significantly negatively associated with age (calbindin, somatostatin, cholecystokinin), whereas 3 synapse-related genes showed significant age-related expression change (PSD95, GAP43, VGLUT1). On covarying for 2 glial markers (GFAP, IBA1), all 3 interneuron genes and 1 synaptic gene (Growth-associated protein 43) remained significant. Two genes were significantly associated with total brain volume (calbindin, complexin 2) and a marker of synaptic density (synaptophysin) was significantly associated with cortical gray matter volume. Age-related change in expression of genes involved in maintenance of inhibition-excitation balance and regulation of prefrontocortical network dynamics suggests these pathways may contribute to brain aging.
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Affiliation(s)
- Adith Mohan
- Centre for Healthy Brain Ageing (CHeBA), University of New South Wales (UNSW) Australia, Sydney, New South Wales, Australia; School of Psychiatry, UNSW Australia, Sydney, New South Wales, Australia; Neuropsychiatric Institute, Prince of Wales Hospital, Randwick, New South Wales, Australia.
| | - Anbupalam Thalamuthu
- Centre for Healthy Brain Ageing (CHeBA), University of New South Wales (UNSW) Australia, Sydney, New South Wales, Australia
| | - Karen A Mather
- Centre for Healthy Brain Ageing (CHeBA), University of New South Wales (UNSW) Australia, Sydney, New South Wales, Australia
| | - Yiru Zhang
- Schizophrenia Research Laboratory, Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Vibeke S Catts
- Schizophrenia Research Laboratory, Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Cynthia Shannon Weickert
- School of Psychiatry, UNSW Australia, Sydney, New South Wales, Australia; Schizophrenia Research Laboratory, Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Perminder S Sachdev
- Centre for Healthy Brain Ageing (CHeBA), University of New South Wales (UNSW) Australia, Sydney, New South Wales, Australia; School of Psychiatry, UNSW Australia, Sydney, New South Wales, Australia; Neuropsychiatric Institute, Prince of Wales Hospital, Randwick, New South Wales, Australia
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48
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Kyle CT, Permenter MR, Vogt JA, Rapp PR, Barnes CA. Behavioral Impact of Long-Term Chronic Implantation of Neural Recording Devices in the Rhesus Macaque. Neuromodulation 2018; 22:435-440. [PMID: 30016006 DOI: 10.1111/ner.12794] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/08/2018] [Accepted: 03/28/2018] [Indexed: 11/28/2022]
Abstract
BACKGROUND Ensemble recording methods are pervasive in basic and clinical neuroscience research. Invasive neural implants are used in patients with drug resistant epilepsy to localize seizure origin, in neuropsychiatric or Parkinson's patients to alleviate symptoms via deep brain stimulation, and with animal models to conduct basic research. Studies addressing the brain's physiological response to chronic electrode implants demonstrate that the mechanical trauma of insertion is followed by an acute inflammatory response as well as a chronic foreign body response. Despite use of invasive recording methods with animal models and humans, little is known of their effect on behavior in healthy populations. OBJECTIVE To quantify the effect of chronic electrode implantation targeting the hippocampus on recognition memory performance. METHODS Four healthy female rhesus macaques were tested in a delayed nonmatching-to-sample (DNMS) recognition memory task before and after hippocampal implantation with a tetrode array device. RESULTS Trials to criterion and recognition memory performance were not significantly different before vs. after chronic electrode implantation. CONCLUSION Our results suggest that chronic implants did not produce significant impairments on DNMS performance.
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Affiliation(s)
- Colin T Kyle
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA
| | - Michele R Permenter
- California National Primate Research Center, University of California, Davis, Davis, CA, USA
| | - Julie A Vogt
- California National Primate Research Center, University of California, Davis, Davis, CA, USA
| | - Peter R Rapp
- Laboratory of Behavioral Neuroscience, Biomedical Research Center, National Institute on Aging, Baltimore, MD, USA
| | - Carol A Barnes
- Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, USA.,Division of Neural Systems, Memory, and Aging, University of Arizona, Tucson, AZ, USA.,Department of Psychology, University of Arizona, Tucson, AZ, USA.,Department of Neurology, University of Arizona, Tucson, AZ, USA.,Department of Neuroscience, University of Arizona, Tucson, AZ, USA
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49
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Galloway CR, Ravipati K, Singh S, Lebois EP, Cohen RM, Levey AI, Manns JR. Hippocampal place cell dysfunction and the effects of muscarinic M 1 receptor agonism in a rat model of Alzheimer's disease. Hippocampus 2018; 28:568-585. [PMID: 29742799 DOI: 10.1002/hipo.22961] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 04/02/2018] [Accepted: 05/06/2018] [Indexed: 11/09/2022]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disease that disproportionately impacts memory and the hippocampus. However, it is unclear how AD pathology influences the activity of surviving neurons in the hippocampus to contribute to the memory symptoms in AD. One well-understood connection between spatial memory and neuronal activity in healthy brains is the activity of place cells, neurons in the hippocampus that fire preferentially in a specific location of a given environment (the place field of the place cell). In the present study, place cells were recorded from the hippocampus in a recently-developed rat model of AD (Tg-F344 AD) at an age (12-20 months) at which the AD rats showed marked spatial memory deficits. Place cells in the CA2 and CA3 pyramidal regions of the hippocampus in AD rats showed sharply reduced spatial fidelity relative to wild-type (WT) rats. In contrast, spiking activity of place cells recorded in region CA1 in AD rats showed good spatial fidelity that was similar to CA1 place cells in WT rats. Oral administration of the M1 muscarinic acetylcholine receptor agonist VU0364572 impacted place cell firing rates in CA1 and CA2/3 hippocampal regions, but did not improve the spatial fidelity of CA2/3 hippocampal place cells in AD rats. The results indicated that, to the extent the spatial memory impairment in AD rats was attributable to hippocampal dysfunction, the memory impairment was more attributable to dysfunction in hippocampal regions CA2 and CA3 rather than CA1.
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Affiliation(s)
| | - Kaushik Ravipati
- Neuroscience and Behavioral Biology Program, Emory University, Atlanta, Georgia
| | - Suyashi Singh
- Neuroscience and Behavioral Biology Program, Emory University, Atlanta, Georgia
| | - Evan P Lebois
- Internal Medicine Research Unit, Pfizer Inc, Cambridge, Massachusetts
| | - Robert M Cohen
- Department of Psychiatry, Emory University, Atlanta, Georgia
| | - Allan I Levey
- Department of Neurology, Emory University, Atlanta, Georgia
| | - Joseph R Manns
- Department of Psychology, Emory University, Atlanta, Georgia
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50
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Hernandez AR, Reasor JE, Truckenbrod LM, Campos KT, Federico QP, Fertal KE, Lubke KN, Johnson SA, Clark BJ, Maurer AP, Burke SN. Dissociable effects of advanced age on prefrontal cortical and medial temporal lobe ensemble activity. Neurobiol Aging 2018; 70:217-232. [PMID: 30031931 PMCID: PMC6829909 DOI: 10.1016/j.neurobiolaging.2018.06.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 06/20/2018] [Accepted: 06/21/2018] [Indexed: 11/25/2022]
Abstract
The link between age-related cellular changes within brain regions and larger scale neuronal ensemble dynamics critical for cognition has not been fully elucidated. The present study measured neuron activity within medial prefrontal cortex (PFC), perirhinal cortex (PER), and hippocampal subregion CA1 of young and aged rats by labeling expression of the immediate-early gene Arc. The proportion of cells expressing Arc was quantified at baseline and after a behavior that requires these regions. In addition, PER and CA1 projection neurons to PFC were identified with retrograde labeling. Within CA1, no age-related differences in neuronal activity were observed in the entire neuron population or within CA1 pyramidal cells that project to PFC. Although behavior was comparable across age groups, behaviorally driven Arc expression was higher in the deep layers of both PER and PFC and lower in the superficial layers of these regions. Moreover, age-related changes in activity levels were most evident within PER cells that project to PFC. These data suggest that the PER-PFC circuit is particularly vulnerable in advanced age.
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Affiliation(s)
- Abbi R Hernandez
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Jordan E Reasor
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Leah M Truckenbrod
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Keila T Campos
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Quinten P Federico
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Kaeli E Fertal
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Katelyn N Lubke
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Sarah A Johnson
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL
| | - Benjamin J Clark
- Department of Psychology, University of New Mexico, Albuquerque, New Mexico
| | - Andrew P Maurer
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL; Department of Biomedical Engineering, University of Florida, Gainesville, FL
| | - Sara N Burke
- McKnight Brain Institute, Department of Neuroscience, University of Florida, Gainesville, FL; Institute on Aging, University of Florida, Gainesville, FL.
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