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Lopez MR, Wasberg SMH, Gagliardi CM, Normandin ME, Muzzio IA. Mystery of the memory engram: History, current knowledge, and unanswered questions. Neurosci Biobehav Rev 2024; 159:105574. [PMID: 38331127 DOI: 10.1016/j.neubiorev.2024.105574] [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: 09/18/2023] [Revised: 12/22/2023] [Accepted: 02/03/2024] [Indexed: 02/10/2024]
Abstract
The quest to understand the memory engram has intrigued humans for centuries. Recent technological advances, including genetic labelling, imaging, optogenetic and chemogenetic techniques, have propelled the field of memory research forward. These tools have enabled researchers to create and erase memory components. While these innovative techniques have yielded invaluable insights, they often focus on specific elements of the memory trace. Genetic labelling may rely on a particular immediate early gene as a marker of activity, optogenetics may activate or inhibit one specific type of neuron, and imaging may capture activity snapshots in a given brain region at specific times. Yet, memories are multifaceted, involving diverse arrays of neuronal subpopulations, circuits, and regions that work in concert to create, store, and retrieve information. Consideration of contributions of both excitatory and inhibitory neurons, micro and macro circuits across brain regions, the dynamic nature of active ensembles, and representational drift is crucial for a comprehensive understanding of the complex nature of memory.
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Affiliation(s)
- M R Lopez
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine and Science, Rochester, MN, United States
| | - S M H Wasberg
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - C M Gagliardi
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - M E Normandin
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - I A Muzzio
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA.
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2
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Lapato AS, Thompson SM, Parra K, Tiwari-Woodruff SK. Astrocyte Glutamate Uptake and Water Homeostasis Are Dysregulated in the Hippocampus of Multiple Sclerosis Patients With Seizures. ASN Neuro 2020; 12:1759091420979604. [PMID: 33297722 PMCID: PMC7734542 DOI: 10.1177/1759091420979604] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
While seizure disorders are more prevalent among multiple sclerosis (MS) patients than the population overall and prognosticate earlier death & disability, their etiology remains unclear. Translational data indicate perturbed expression of astrocytic molecules contributing to homeostatic neuronal excitability, including water channels (AQP4) and synaptic glutamate transporters (EAAT2), in a mouse model of MS with seizures (MS+S). However, astrocytes in MS+S have not been examined. To assess the translational relevance of astrocyte dysfunction observed in a mouse model of MS+S, demyelinated lesion burden, astrogliosis, and astrocytic biomarkers (AQP4/EAAT2/ connexin-CX43) were evaluated by immunohistochemistry in postmortem hippocampi from MS & MS+S donors. Lesion burden was comparable in MS & MS+S cohorts, but astrogliosis was elevated in MS+S CA1 with a concomitant decrease in EAAT2 signal intensity. AQP4 signal declined in MS+S CA1 & CA3 with a loss of perivascular AQP4 in CA1. CX43 expression was increased in CA3. Together, these data suggest that hippocampal astrocytes from MS+S patients display regional differences in expression of molecules associated with glutamate buffering and water homeostasis that could exacerbate neuronal hyperexcitability. Importantly, mislocalization of CA1 perivascular AQP4 seen in MS+S is analogous to epileptic hippocampi without a history of MS, suggesting convergent pathophysiology. Furthermore, as neuropathology was concentrated in MS+S CA1, future study is warranted to determine the pathophysiology driving regional differences in glial function in the context of seizures during demyelinating disease.
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Affiliation(s)
- Andrew S Lapato
- Division of Biomedical Sciences, UCR School of Medicine, Riverside, California, United States.,Center for Glial-Neuronal Interaction, UCR School of Medicine, Riverside, California, United States
| | - Sarah M Thompson
- Division of Biomedical Sciences, UCR School of Medicine, Riverside, California, United States
| | - Karen Parra
- Division of Biomedical Sciences, UCR School of Medicine, Riverside, California, United States
| | - Seema K Tiwari-Woodruff
- Division of Biomedical Sciences, UCR School of Medicine, Riverside, California, United States.,Center for Glial-Neuronal Interaction, UCR School of Medicine, Riverside, California, United States.,Department of Neuroscience, UCR School of Medicine, Riverside, California, United States
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3
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Kiffer F, Alexander T, Anderson J, Groves T, McElroy T, Wang J, Sridharan V, Bauer M, Boerma M, Allen A. Late Effects of 1H + 16O on Short-Term and Object Memory, Hippocampal Dendritic Morphology and Mutagenesis. Front Behav Neurosci 2020; 14:96. [PMID: 32670032 PMCID: PMC7332779 DOI: 10.3389/fnbeh.2020.00096] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Accepted: 05/22/2020] [Indexed: 11/17/2022] Open
Abstract
The space extending beyond Earth’s magnetosphere is subject to a complex field of high-energy charged nuclei, which are capable of traversing spacecraft shielding and human tissues, inducing dense ionization events. The central nervous system is a major area of concern for astronauts who will be exposed to the deep-space radiation environment on a mission to Mars, as charged-particle radiation has been shown to elicit changes to the dendritic arbor within the hippocampus of rodents, and related cognitive-behavioral deficits. We exposed 6-month-old male mice to whole-body 1H (0.5 Gy; 150 MeV/n; 18–19 cGy/minute) and an hour later to 16O (0.1Gy; 600 MeV/n; 18–33 Gy/min) at NASA’s Space Radiation Laboratory as a galactic cosmic ray-relevant model. Animals were housed with bedding which provides cognitive enrichment. Mice were tested for cognitive behavior 9 months after exposure to elucidate late radiation effects. Radiation induced significant deficits in novel object recognition and short-term spatial memory (Y-maze). Additionally, we observed opposing morphological differences between the mature granular and pyramidal neurons throughout the hippocampus, with increased dendritic length in the dorsal dentate gyrus and reduced length and complexity in the CA1 subregion of the hippocampus. Dendritic spine analyses revealed a severe reduction in mushroom spine density throughout the hippocampus of irradiated animals. Finally, we detected no general effect of radiation on single-nucleotide polymorphisms in immediate early genes, and genes involved in inflammation but found a higher variant allele frequency in the antioxidants thioredoxin reductase 2 and 3 loci.
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Affiliation(s)
- Frederico Kiffer
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Tyler Alexander
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Julie Anderson
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Thomas Groves
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Taylor McElroy
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Jing Wang
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Vijayalakshmi Sridharan
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Michael Bauer
- Department of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Marjan Boerma
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Antiño Allen
- Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States.,Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, United States
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4
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Kiffer F, Howe AK, Carr H, Wang J, Alexander T, Anderson JE, Groves T, Seawright JW, Sridharan V, Carter G, Boerma M, Allen AR. Late effects of 1H irradiation on hippocampal physiology. LIFE SCIENCES IN SPACE RESEARCH 2018; 17:51-62. [PMID: 29753414 PMCID: PMC7063743 DOI: 10.1016/j.lssr.2018.03.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 03/07/2018] [Accepted: 03/10/2018] [Indexed: 05/21/2023]
Abstract
NASA's Missions to Mars and beyond will expose flight crews to potentially dangerous levels of charged-particle radiation. Of all charged nuclei, 1H is the most abundant charged particle in both the galactic cosmic ray (GCR) and solar particle event (SPE) spectra. There are currently no functional spacecraft shielding materials that are able to mitigate the charged-particle radiation encountered in space. Recent studies have demonstrated cognitive injuries due to high-dose 1H exposures in rodents. Our study investigated the effects of 1H irradiation on neuronal morphology in the hippocampus of adult male mice. 6-month-old mice received whole-body exposure to 1H at 0.5 and 1 Gy (150 MeV/n; 0.35-0.55 Gy/min) at NASA's Space Radiation Laboratory in Upton, NY. At 9-months post-irradiation, we tested each animal's open-field exploratory performance. After sacrifice, we dissected the brains along the midsagittal plane, and then either fixed or dissected further and snap-froze them. Our data showed that exposure to 0.5 Gy or 1 Gy 1H significantly increased animals' anxiety behavior in open-field testing. Our micromorphometric analyses revealed significant decreases in mushroom spine density and dendrite morphology in the Dentate Gyrus, Cornu Ammonis 3 and 1 of the hippocampus, and lowered expression of synaptic markers. Our data suggest 1H radiation significantly increased exploration anxiety and modulated the dendritic spine and dendrite morphology of hippocampal neurons at a dose of 0.5 or 1 Gy.
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Affiliation(s)
- Frederico Kiffer
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Alexis K Howe
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Hannah Carr
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Jing Wang
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Tyler Alexander
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Julie E Anderson
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Thomas Groves
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - John W Seawright
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Vijayalakshmi Sridharan
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Gwendolyn Carter
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Marjan Boerma
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Antiño R Allen
- Division of Radiation Health at the University of Arkansas for Medical Sciences, 4301 West Markham, Suite 441B-2, Little Rock, AR 72205, United States; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States; Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
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Acevedo-Triana CA, Rojas MJ, Cardenas FP. Running wheel training does not change neurogenesis levels or alter working memory tasks in adult rats. PeerJ 2017; 5:e2976. [PMID: 28503368 PMCID: PMC5426350 DOI: 10.7717/peerj.2976] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 01/10/2017] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Exercise can change cellular structure and connectivity (neurogenesis or synaptogenesis), causing alterations in both behavior and working memory. The aim of this study was to evaluate the effect of exercise on working memory and hippocampal neurogenesis in adult male Wistar rats using a T-maze test. METHODS An experimental design with two groups was developed: the experimental group (n = 12) was subject to a forced exercise program for five days, whereas the control group (n = 9) stayed in the home cage. Six to eight weeks after training, the rats' working memory was evaluated in a T-maze test and four choice days were analyzed, taking into account alternation as a working memory indicator. Hippocampal neurogenesis was evaluated by means of immunohistochemistry of BrdU positive cells. RESULTS No differences between groups were found in the behavioral variables (alternation, preference index, time of response, time of trial or feeding), or in the levels of BrdU positive cells. DISCUSSION Results suggest that although exercise may have effects on brain structure, a construct such as working memory may require more complex changes in networks or connections to demonstrate a change at behavioral level.
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Affiliation(s)
| | - Manuel J. Rojas
- Animal Health Department, Universidad Nacional de Colombia, Bogotá, Colombia
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Cortez I, Bulavin DV, Wu P, McGrath EL, Cunningham KA, Wakamiya M, Papaconstantinou J, Dineley KT. Aged dominant negative p38α MAPK mice are resistant to age-dependent decline in adult-neurogenesis and context discrimination fear conditioning. Behav Brain Res 2016; 322:212-222. [PMID: 27765672 DOI: 10.1016/j.bbr.2016.10.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 10/10/2016] [Accepted: 10/12/2016] [Indexed: 01/13/2023]
Abstract
A major aspect of mammalian aging is the decline in functional competence of many self-renewing cell types, including adult-born neuronal precursors. Since age-related senescence of self-renewal occurs simultaneously with chronic up-regulation of the p38MAPKalpha (p38α) signaling pathway, we used the dominant negative mouse model for attenuated p38α activity (DN-p38αAF/+) in which Thr180 and Tyr182 are mutated (T→A/Y→F) to prevent phosphorylation activation (DN-p38αAF/+) and kinase activity. As a result, aged DN-p38αAF/+ mice are resistant to age-dependent decline in proliferation and regeneration of several peripheral tissue progenitors when compared to wild-type littermates. Aging is the major risk factor for non-inherited forms of Alzheimer's disease (AD); environmental and genetic risk factors that accelerate the senescence phenotype are thought to contribute to an individual's relative risk. In the present study, we evaluated aged DN-p38αAF/+ and wildtype littermates in a series of behavioral paradigms to test if p38α mutant mice exhibit altered baseline abnormalities in neurological reflexes, locomotion, anxiety-like behavior, and age-dependent cognitive decline. While aged DN-p38αAF/+ and wildtype littermates appear equal in all tested baseline neurological and behavioral parameters, DN-p38αAF/+ exhibit superior context discrimination fear conditioning. Context discrimination is a cognitive task that is supported by proliferation and differentiation of adult-born neurons in the dentate gyrus of the hippocampus. Consistent with enhanced context discrimination in aged DN-p38αAF/+, we discovered enhanced production of adult-born neurons in the dentate gyrus of DN-p38αAF/+ mice compared to wildtype littermates. Our findings support the notion that p38α inhibition has therapeutic utility in aging diseases that affect cognition, such as AD.
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Affiliation(s)
- IbDanelo Cortez
- Department of Neurology, University of Texas Medical Branch at Galveston, Galveston TX, USA; Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch at Galveston, Galveston TX, USA; Center for Addiction Research, University of Texas Medical Branch at Galveston, Galveston TX, USA.
| | - Dmitry V Bulavin
- Institute for Research on Cancer and Ageing of Nice, INSERM, University of Nice, France
| | - Ping Wu
- Department of Neuroscience & Cell Biology, University of Texas Medical Branch at Galveston, Galveston TX, USA
| | - Erica L McGrath
- Department of Neuroscience & Cell Biology, University of Texas Medical Branch at Galveston, Galveston TX, USA
| | - Kathryn A Cunningham
- Department of Pharmacology and Toxicology, University of Texas Medical Branch at Galveston, Galveston TX, USA; Center for Addiction Research, University of Texas Medical Branch at Galveston, Galveston TX, USA
| | - Maki Wakamiya
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston TX, USA; Transgenic Mouse Core Facility, University of Texas Medical Branch at Galveston, Galveston TX, USA
| | - John Papaconstantinou
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch at Galveston, Galveston TX, USA
| | - Kelly T Dineley
- Department of Neurology, University of Texas Medical Branch at Galveston, Galveston TX, USA; Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch at Galveston, Galveston TX, USA; Center for Addiction Research, University of Texas Medical Branch at Galveston, Galveston TX, USA
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7
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Nagai MK, Marquez-Chin C, Popovic MR. Why Is Functional Electrical Stimulation Therapy Capable of Restoring Motor Function Following Severe Injury to the Central Nervous System? Transl Neurosci 2016. [DOI: 10.1007/978-1-4899-7654-3_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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8
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Lepousez G, Nissant A, Lledo PM. Adult Neurogenesis and the Future of the Rejuvenating Brain Circuits. Neuron 2015; 86:387-401. [DOI: 10.1016/j.neuron.2015.01.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Canales JJ, Ferrer-Donato A. Prenatal Exposure to Alcohol and 3,4-Methylenedioxymethamphetamine (Ecstasy) Alters Adult Hippocampal Neurogenesis and Causes Enduring Memory Deficits. Dev Neurosci 2014; 36:10-7. [DOI: 10.1159/000356820] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 10/25/2013] [Indexed: 11/19/2022] Open
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10
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Agis-Balboa RC, Fischer A. Generating new neurons to circumvent your fears: the role of IGF signaling. Cell Mol Life Sci 2014; 71:21-42. [PMID: 23543251 PMCID: PMC11113432 DOI: 10.1007/s00018-013-1316-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 02/12/2013] [Accepted: 03/04/2013] [Indexed: 12/13/2022]
Abstract
Extinction of fear memory is a particular form of cognitive function that is of special interest because of its involvement in the treatment of anxiety and mood disorders. Based on recent literature and our previous findings (EMBO J 30(19):4071-4083, 2011), we propose a new hypothesis that implies a tight relationship among IGF signaling, adult hippocampal neurogenesis and fear extinction. Our proposed model suggests that fear extinction-induced IGF2/IGFBP7 signaling promotes the survival of neurons at 2-4 weeks old that would participate in the discrimination between the original fear memory trace and the new safety memory generated during fear extinction. This is also called "pattern separation", or the ability to distinguish similar but different cues (e.g., context). To understand the molecular mechanisms underlying fear extinction is therefore of great clinical importance.
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Affiliation(s)
- R C Agis-Balboa
- Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Grisebach Str. 5, 37077, Göttingen, Germany,
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Adult neurogenesis in the olfactory system shapes odor memory and perception. PROGRESS IN BRAIN RESEARCH 2014; 208:157-75. [PMID: 24767482 DOI: 10.1016/b978-0-444-63350-7.00006-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The olfactory system is a dynamic place. In mammals, not only are sensory neurons located in the sensory organ renewed through adult life, but also its first central relay is reconstructed by continuous neuronal recruitment. Despite these numerous morphological and physiological changes, olfaction is a unique sensory modality endowed with a privileged link to memory. This raises a clear conundrum; how does the olfactory system balance its neuronal turnover with its participation in long-term memory? This review concentrates on the functional aspects of adult neurogenesis, addressing how the integration of late-born neurons participates in olfactory perception and memory. After outlining the properties of adult neurogenesis in the olfactory system, and after describing their regulation by internal and environmental factors, we ask how the process of odorant perception can be influenced by constant neuronal turnover. We then explore the possible functional roles that newborn neurons might have for olfactory memory. Throughout this review, and as we concentrate almost exclusively on mammalian models, we stress the idea that adult neurogenesis is yet another form of plasticity used by the brain to copes with a constantly changing olfactory world.
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Abstract
Neurotransmitter gamma-aminobutiric acid (GABA) through ionotropic GABAA and metabotropic GABAB receptors plays key roles in modulating the development, plasticity and function of neuronal networks. GABA is inhibitory in mature neurons but excitatory in immature neurons, neuroblasts and neural stem/progenitor cells (NSCs/NPCs). The switch from excitatory to inhibitory occurs following the development of glutamatergic synaptic input and results from the dynamic changes in the expression of Na+/K+/2Cl- co-transporter NKCC1 driving Cl- influx and neuron-specific K+/Cl- co-transporter KCC2 driving Cl- efflux. The developmental transition of KCC2 expression is regulated by Disrupted-in-Schizophrenia 1 (DISC1) and brain-derived neurotrophic factor (BDNF) signaling. The excitatory GABA signaling during early neurogenesis is important to the activity/experience-induced regulation of NSC quiescence, NPC proliferation, neuroblast migration and newborn neuronal maturation/functional integration. The inhibitory GABA signaling allows for the sparse and static functional networking essential for learning/memory development and maintenance.
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Affiliation(s)
- Adalto Pontes
- Department of Neuroscience, Temple University School of Medicine, Philadelphia, PA 19140, USA ; Universidade do Estado do Pará, Santarém, PA, Brasil
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de Oliveira MF, Pinto FCG, Nishikuni K, Botelho RV, Lima AM, Rotta JM. Revisiting hydrocephalus as a model to study brain resilience. Front Hum Neurosci 2012; 5:181. [PMID: 22232589 PMCID: PMC3252565 DOI: 10.3389/fnhum.2011.00181] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 12/18/2011] [Indexed: 11/17/2022] Open
Abstract
Hydrocephalus is an entity which embraces a variety of diseases whose final result is the enlarged size of cerebral ventricular system, partially or completely. The physiopathology of hydrocephalus lies in the dynamics of circulation of cerebrospinal fluid (CSF). The consequent CSF stasis in hydrocephalus interferes with cerebral and ventricular system development. Children and adults who sustain congenital or acquired brain injury typically experience a diffuse insult that impacts many areas of the brain. Development and recovery after such injuries reflects both restoration and reorganization of cognitive functions. Classic examples were already reported in literature. This suggests the presence of biological mechanisms associated with resilient adaptation of brain networks. We will settle a link between the notable modifications to neurophysiology secondary to hydrocephalus and the ability of neuronal tissue to reassume and reorganize its functions.
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