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Hendrickson AS, Francis KL, Kumar A, Le JP, Scarlett JM, Keene CD, Tovar DA, Alonge KM. Assessing translational applicability of perineuronal net dysfunction in Alzheimer's disease across species. Front Neurosci 2024; 18:1396101. [PMID: 38745932 PMCID: PMC11091253 DOI: 10.3389/fnins.2024.1396101] [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: 03/05/2024] [Accepted: 04/12/2024] [Indexed: 05/16/2024] Open
Abstract
In the context of aging and age-associated neurodegenerative disorders, the brain's extracellular matrix (ECM) serves as a critical regulator for neuronal health and cognitive function. Within the extracellular space, proteoglycans and their glycosaminoglycan attachments play essential roles in forming, stabilizing, and protecting neural circuits throughout neurodevelopment and adulthood. Recent studies in rodents reveal that chondroitin sulfate-glycosaminoglycan (CS-GAG) containing perineuronal nets (PNNs) exhibit both structural and compositional differences throughout the brain. While animal studies are illuminating, additional research is required to translate these interregional PNN/CS-GAG variations to human brain tissue. In this perspective article, we first investigate the translational potential for interregional CS-GAG variances across species as novel targets for region-specific therapeutic development. We specifically focus on the observation that alterations in brain PNN-associated CS-GAGs have been linked with the progression of Alzheimer's disease (AD) neuropathology in humans, but these changes have not been fully recapitulated in rodent models of this disease. A second highlight of this perspective article investigates whether AD-associated shifts in CS-GAGs in humans may be dependent on region-specific baseline differences in CS-GAG sulfation patterning. The current findings begin to disentangle the intricate relationships between the interregional differences in brain PNN/CS-GAG matrices across species, while emphasizing the need to better understand the close relationship between dementia and changes in brain CS-GAG sulfation patterns in patients with AD and related dementias.
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Affiliation(s)
- Aarun S. Hendrickson
- Medicinal Chemistry, University of Washington, Seattle, WA, United States
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA, United States
| | - Kendra L. Francis
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA, United States
- Department of Pediatric Gastroenterology and Hepatology, Seattle Children’s Hospital, Seattle, WA, United States
| | - Asmit Kumar
- Medicinal Chemistry, University of Washington, Seattle, WA, United States
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA, United States
| | - Jaden P. Le
- Medicinal Chemistry, University of Washington, Seattle, WA, United States
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA, United States
| | - Jarrad M. Scarlett
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA, United States
- Department of Pediatric Gastroenterology and Hepatology, Seattle Children’s Hospital, Seattle, WA, United States
| | - C. Dirk Keene
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States
| | - David A. Tovar
- Department of Psychology, Vanderbilt University, Nashville, TN, United States
| | - Kimberly M. Alonge
- Medicinal Chemistry, University of Washington, Seattle, WA, United States
- Department of Medicine, University of Washington Medicine Diabetes Institute, Seattle, WA, United States
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Tallman CW, Luo Z, Smith CN. Human brain activity and functional connectivity associated with verbal long-term memory consolidation across 1 month. Front Hum Neurosci 2024; 18:1342552. [PMID: 38450223 PMCID: PMC10915245 DOI: 10.3389/fnhum.2024.1342552] [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: 11/22/2023] [Accepted: 01/22/2024] [Indexed: 03/08/2024] Open
Abstract
Introduction Declarative memories are initially dependent on the hippocampus and become stabilized through the neural reorganization of connections between the medial temporal lobe and neocortex. The exact time-course of these neural changes is not well established, although time-dependent changes in retrieval-related brain function can be detected across relatively short time periods in humans (e.g., hours to months). Methods In a study involving older adults with normal cognition (N = 24), we investigated changes in brain activity and functional connectivity associated with the long-term memory consolidation of verbal material over one month. Participants studied fact-like, three-word sentences at 1-month, 1-week, 1-day, and 1-hour intervals before a recognition memory test inside an MRI scanner. Old/new recognition with confidence ratings and response times were recorded. We examined whole-brain changes in retrieval-related brain activity, as well as functional connectivity of the hippocampus and ventromedial prefrontal cortex (vmPFC), as memories aged from 1 hour to 1 month. Secondary analyses minimized the effect of confounding factors affected by memory age (i.e., changes in confidence and response time or re-encoding of targets). Results Memory accuracy, confidence ratings, and response times changed with memory age. A memory age network was identified where retrieval-related brain activity in cortical regions increased or decreased as a function of memory age. Hippocampal brain activity in an anatomical region of interest decreased with memory age. Importantly, these changes in retrieval-related activity were not confounded with changes in activity related to concomitant changes in behavior or encoding. Exploratory analyses of vmPFC functional connectivity as a function of memory age revealed increased connectivity with the posterior parietal cortex, as well as with the vmPFC itself. In contrast, hippocampal functional connectivity with the vmPFC and orbitofrontal cortex decreased with memory age. Discussion The observed changes in retrieval-related brain activity and functional connectivity align with the predictions of standard systems consolidation theory. These results suggest that processes consistent with long-term memory consolidation can be identified over short time periods using fMRI, particularly for verbal material.
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Affiliation(s)
- Catherine W. Tallman
- Department of Psychology, University of California, San Diego, San Diego, CA, United States
- Veterans Affairs San Diego Healthcare System, Department of Research Service, San Diego, CA, United States
| | - Zhishang Luo
- Veterans Affairs San Diego Healthcare System, Department of Research Service, San Diego, CA, United States
- Halıcıoğlu Data Science Institute, University of California, San Diego, San Diego, CA, United States
| | - Christine N. Smith
- Veterans Affairs San Diego Healthcare System, Department of Research Service, San Diego, CA, United States
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
- Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA, United States
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Brosens N, Lesuis SL, Bassie I, Reyes L, Gajadien P, Lucassen PJ, Krugers HJ. Elevated corticosterone after fear learning impairs remote auditory memory retrieval and alters brain network connectivity. Learn Mem 2023; 30:125-132. [PMID: 37487708 PMCID: PMC10519398 DOI: 10.1101/lm.053836.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 06/23/2023] [Indexed: 07/26/2023]
Abstract
Glucocorticoids are potent memory modulators that can modify behavior in an adaptive or maladaptive manner. Elevated glucocorticoid levels after learning promote memory consolidation at recent time points, but their effects on remote time points are not well established. Here we set out to assess whether corticosterone (CORT) given after learning modifies remote fear memory. To that end, mice were exposed to a mild auditory fear conditioning paradigm followed by a single 2 mg/kg CORT injection, and after 28 d, auditory memory was assessed. Neuronal activation was investigated using immunohistochemistry for the immediate early gene c-Fos, and coactivation of brain regions was determined using a correlation matrix analysis. CORT-treated mice displayed significantly less remote auditory memory retrieval. While the net activity of studied brain regions was similar compared with the control condition, CORT-induced remote memory impairment was associated with altered correlated activity between brain regions. Specifically, connectivity of the lateral amygdala with the basal amygdala and the dorsal dentate gyrus was significantly reduced in CORT-treated mice, suggesting disrupted network connectivity that may underlie diminished remote memory retrieval. Elucidating the pathways underlying these effects could help provide mechanistic insight into the effects of stress on memory and possibly provide therapeutic targets for psychopathology.
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Affiliation(s)
- Niek Brosens
- Brain Plasticity Group, Swammerdam Institute for Life Sciences (SILS)-Cognitive and Systems Neuroscience (CNS), University of Amsterdam, Amsterdam 1098 XH, the Netherlands
| | - Sylvie L Lesuis
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
| | - Ilse Bassie
- Brain Plasticity Group, Swammerdam Institute for Life Sciences (SILS)-Cognitive and Systems Neuroscience (CNS), University of Amsterdam, Amsterdam 1098 XH, the Netherlands
| | - Lara Reyes
- Brain Plasticity Group, Swammerdam Institute for Life Sciences (SILS)-Cognitive and Systems Neuroscience (CNS), University of Amsterdam, Amsterdam 1098 XH, the Netherlands
| | - Priya Gajadien
- Brain Plasticity Group, Swammerdam Institute for Life Sciences (SILS)-Cognitive and Systems Neuroscience (CNS), University of Amsterdam, Amsterdam 1098 XH, the Netherlands
| | - Paul J Lucassen
- Brain Plasticity Group, Swammerdam Institute for Life Sciences (SILS)-Cognitive and Systems Neuroscience (CNS), University of Amsterdam, Amsterdam 1098 XH, the Netherlands
| | - Harm J Krugers
- Brain Plasticity Group, Swammerdam Institute for Life Sciences (SILS)-Cognitive and Systems Neuroscience (CNS), University of Amsterdam, Amsterdam 1098 XH, the Netherlands
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Tambini A, Miller J, Ehlert L, Kiyonaga A, D’Esposito M. Structured memory representations develop at multiple time scales in hippocampal-cortical networks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.06.535935. [PMID: 37066263 PMCID: PMC10104124 DOI: 10.1101/2023.04.06.535935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Influential views of systems memory consolidation posit that the hippocampus rapidly forms representations of specific events, while neocortical networks extract regularities across events, forming the basis of schemas and semantic knowledge. Neocortical extraction of schematic memory representations is thought to occur on a protracted timescale of months, especially for information that is unrelated to prior knowledge. However, this theorized evolution of memory representations across extended timescales, and differences in the temporal dynamics of consolidation across brain regions, lack reliable empirical support. To examine the temporal dynamics of memory representations, we repeatedly exposed human participants to structured information via sequences of fractals, while undergoing longitudinal fMRI for three months. Sequence-specific activation patterns emerged in the hippocampus during the first 1-2 weeks of learning, followed one week later by high-level visual cortex, and subsequently the medial prefrontal and parietal cortices. Schematic, sequence-general representations emerged in the prefrontal cortex after 3 weeks of learning, followed by the medial temporal lobe and anterior temporal cortex. Moreover, hippocampal and most neocortical representations showed sustained rather than time-limited dynamics, suggesting that representations tend to persist across learning. These results show that specific hippocampal representations emerge early, followed by both specific and schematic representations at a gradient of timescales across hippocampal-cortical networks as learning unfolds. Thus, memory representations do not exist only in specific brain regions at a given point in time, but are simultaneously present at multiple levels of abstraction across hippocampal-cortical networks.
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Affiliation(s)
- Arielle Tambini
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, NY
- Department of Psychiatry, New York University Grossman School of Medicine, New York, NY
| | - Jacob Miller
- Wu Tsai Institute, Department of Psychiatry, Yale University, New Haven, CT
| | - Luke Ehlert
- Department of Neurobiology and Behavior, University of California. Irvine, CA
| | - Anastasia Kiyonaga
- Department of Cognitive Science, University of California, San Diego, CA
| | - Mark D’Esposito
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA
- Department of Psychology, University of California, Berkeley, CA
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Multiple traces and altered signal-to-noise in systems consolidation: Evidence from the 7T fMRI Natural Scenes Dataset. Proc Natl Acad Sci U S A 2022; 119:e2123426119. [PMID: 36279446 PMCID: PMC9636924 DOI: 10.1073/pnas.2123426119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
How do the neural correlates of recognition change over time? We study natural scene image recognition spanning a year with 7-Tesla functional magnetic resonance imaging (fMRI) of the human brain. We find that the medial temporal lobe (MTL) contribution to recognition persists over 200 d, supporting multiple-trace theory and contradicting a trace transfer (from MTL to cortex) point of view. We then test the hypothesis that the signal-to-noise ratio of traces increases over time, presumably a consequence of synaptic “desaturation” in the weeks following learning. The fMRI trace signature associates with the rate of removal of competing traces and reflects a time-related enhancement of image-feature selectivity. We conclude that multiple MTL traces and improved signal-to-noise may underlie systems-level memory consolidation. The brain mechanisms of memory consolidation remain elusive. Here, we examine blood-oxygen-level-dependent (BOLD) correlates of image recognition through the scope of multiple influential systems consolidation theories. We utilize the longitudinal Natural Scenes Dataset, a 7-Tesla functional magnetic resonance imaging human study in which ∼135,000 trials of image recognition were conducted over the span of a year among eight subjects. We find that early- and late-stage image recognition associates with both medial temporal lobe (MTL) and visual cortex when evaluating regional activations and a multivariate classifier. Supporting multiple-trace theory (MTT), parts of the MTL activation time course show remarkable fit to a 20-y-old MTT time-dynamical model predicting early trace intensity increases and slight subsequent interference (R2 > 0.90). These findings contrast a simplistic, yet common, view that memory traces are transferred from MTL to cortex. Next, we test the hypothesis that the MTL trace signature of memory consolidation should also reflect synaptic “desaturation,” as evidenced by an increased signal-to-noise ratio. We find that the magnitude of relative BOLD enhancement among surviving memories is positively linked to the rate of removal (i.e., forgetting) of competing traces. Moreover, an image-feature and time interaction of MTL and visual cortex functional connectivity suggests that consolidation mechanisms improve the specificity of a distributed trace. These neurobiological effects do not replicate on a shorter timescale (within a session), implicating a prolonged, offline process. While recognition can potentially involve cognitive processes outside of memory retrieval (e.g., re-encoding), our work largely favors MTT and desaturation as perhaps complementary consolidative memory mechanisms.
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Gilmore AW, Audrain S, Martin A. Specifying 'where' and 'what' is critical for testing hippocampal contributions to memory retrieval. Cogn Neurosci 2022; 13:144-146. [PMID: 35586907 PMCID: PMC9808613 DOI: 10.1080/17588928.2022.2076071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Tallman and colleagues' review of consolidation studies found that the length of the delay between 'recent' and 'remote' events is an influential determinant of detecting temporally graded hippocampal activity. Here, we discuss two additional factors - separate analysis of distinct regions within the hippocampus and the use of overt recall methods - that should be considered when testing competing theories of hippocampal contributions to memory.
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Affiliation(s)
- Adrian W. Gilmore
- Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Sam Audrain
- Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Alex Martin
- Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892, USA
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Runyan JD, Brooks NW. Evidence for the standard model, multiple trace theory, or the unified theory? Cogn Neurosci 2022; 13:151-153. [PMID: 35603813 DOI: 10.1080/17588928.2022.2076663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
There have been two dominating theories for memory consolidation: the standard model (SM) and multiple trace theory (MTT). Whereas lesion studies have largely indicated a waning role for the hippocampus in memory consolidation, and thus have supported SM, findings from neuroimaging studies have produced varying results. Tallman et al. (this issue) argue that this variability may result from confounding factors and that, once these factors are accounted for, their neuroimaging results support SM. They do not, however, consider a third option: the unified theory. Here, we suggest that their findings, along with neurobiochemical and engram cell studies, may better fit this third theory.
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Affiliation(s)
- Jason D Runyan
- Psychology Department, Indiana Wesleyan University, Marion, IN, USA
| | - Nathan W Brooks
- Psychology Department, Indiana Wesleyan University, Marion, IN, USA
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Santangelo V. On the contribution of the ventromedial prefrontal cortex to the neural representation of past memories. Cogn Neurosci 2022; 13:154-155. [PMID: 35579493 DOI: 10.1080/17588928.2022.2076072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Tallman and colleagues (this issue) showed that memory consolidation of laboratory materials produces, even at short intervals, changes in cortical activity within a widespread network of brain regions. These changes, however, do not encompass a core memory region, namely the ventromedial prefrontal cortex (vmPFC). Here, I discuss research showing that the neural activity of the vmPFC is sensitive to the remoteness of memories, especially using tasks that involve autobiographical recollection. Taken together, these findings appear to highlight a differential contribution of the vmPFC according to the nature of the to-be-remembered material (laboratory vs. autobiographical) that might be further investigated by future research.
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Affiliation(s)
- Valerio Santangelo
- Department of Philosophy, Social Sciences & Education, University of Perugia, Italy.,Functional Neuroimaging Laboratory, Fondazione Santa Lucia, IRCCS, Rome, Italy
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