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Pytte CL. Adult Neurogenesis in the Songbird: Region-Specific Contributions of New Neurons to Behavioral Plasticity and Stability. BRAIN, BEHAVIOR AND EVOLUTION 2016; 87:191-204. [PMID: 27560148 DOI: 10.1159/000447048] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Our understanding of the role of new neurons in learning and encoding new information has been largely based on studies of new neurons in the mammalian dentate gyrus and olfactory bulb - brain regions that may be specialized for learning. Thus the role of new neurons in regions that serve other functions has yet to be fully explored. The song system provides a model for studying new neuron function in brain regions that contribute differently to song learning, song auditory discrimination, and song motor production. These regions subserve learning as well as long-term storage of previously learned information. This review examines the differences between learning-based and activity-based retention of new neurons and explores the potential contributions of new neurons to behavioral stability in the song motor production pathway.
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Affiliation(s)
- Carolyn L Pytte
- Psychology Department, Queens College and The Graduate Center, City University of New York, Flushing, N.Y., USA
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102
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Kandola A, Hendrikse J, Lucassen PJ, Yücel M. Aerobic Exercise as a Tool to Improve Hippocampal Plasticity and Function in Humans: Practical Implications for Mental Health Treatment. Front Hum Neurosci 2016; 10:373. [PMID: 27524962 PMCID: PMC4965462 DOI: 10.3389/fnhum.2016.00373] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 07/11/2016] [Indexed: 12/24/2022] Open
Abstract
Aerobic exercise (AE) has been widely praised for its potential benefits to cognition and overall brain and mental health. In particular, AE has a potent impact on promoting the function of the hippocampus and stimulating neuroplasticity. As the evidence-base rapidly builds, and given most of the supporting work can be readily translated from animal models to humans, the potential for AE to be applied as a therapeutic or adjunctive intervention for a range of human conditions appears ever more promising. Notably, many psychiatric and neurological disorders have been associated with hippocampal dysfunction, which may underlie the expression of certain symptoms common to these disorders, including (aspects of) cognitive dysfunction. Augmenting existing treatment approaches using AE based interventions may promote hippocampal function and alleviate cognitive deficits in various psychiatric disorders that currently remain untreated. Incorporating non-pharmacological interventions into clinical treatment may also have a number of other benefits to patient well being, such as limiting the risk of adverse side effects. This review incorporates both animal and human literature to comprehensively detail how AE is associated with cognitive enhancements and stimulates a cascade of neuroplastic mechanisms that support improvements in hippocampal functioning. Using the examples of schizophrenia and major depressive disorder, the utility and implementation of an AE intervention to the clinical domain will be proposed, aimed to reduce cognitive deficits in these, and related disorders.
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Affiliation(s)
- Aaron Kandola
- Brain and Mental Health Lab, School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, MelbourneVIC, Australia; Amsterdam Brain and Cognition, University of AmsterdamAmsterdam, Netherlands
| | - Joshua Hendrikse
- Brain and Mental Health Lab, School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne VIC, Australia
| | - Paul J Lucassen
- Centre for Neuroscience, Swammerdam Institute of Life Sciences, University of Amsterdam Amsterdam, Netherlands
| | - Murat Yücel
- Brain and Mental Health Lab, School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne VIC, Australia
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103
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Nehls M. Unified theory of Alzheimer's disease (UTAD): implications for prevention and curative therapy. J Mol Psychiatry 2016; 4:3. [PMID: 27429752 PMCID: PMC4947325 DOI: 10.1186/s40303-016-0018-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/03/2016] [Indexed: 12/14/2022] Open
Abstract
The aim of this review is to propose a Unified Theory of Alzheimer's disease (UTAD) that integrates all key behavioural, genetic and environmental risk factors in a causal chain of etiological and pathogenetic events. It is based on three concepts that emanate from human's evolutionary history: (1) The grandmother-hypothesis (GMH), which explains human longevity due to an evolutionary advantage in reproduction by trans-generational transfer of acquired knowledge. Consequently it is argued that mental health at old-age must be the default pathway of humans' genetic program and not development of AD. (2) Therefore, mechanism like neuronal rejuvenation (NRJ) and adult hippocampal neurogenesis (AHN) that still function efficiently even at old age provide the required lifelong ability to memorize personal experiences important for survival. Cumulative evidence from a multitude of experimental and epidemiological studies indicate that behavioural and environmental risk factors, which impair productive AHN, result in reduced episodic memory performance and in reduced psychological resilience. This leads to avoidance of novelty, dysregulation of the hypothalamic-pituitary-adrenal (HPA)-axis and cortisol hypersecretion, which drives key pathogenic mechanisms of AD like the accumulation and oligomerization of synaptotoxic amyloid beta, chronic neuroinflammation and neuronal insulin resistance. (3) By applying to AHN the law of the minimum (LOM), which defines the basic requirements of biological growth processes, the UTAD explains why and how different lifestyle deficiencies initiate the AD process by impairing AHN and causing dysregulation of the HPA-axis, and how environmental and genetic risk factors such as toxins or ApoE4, respectively, turn into disease accelerators under these unnatural conditions. Consequently, the UTAD provides a rational strategy for the prevention of mental decline and a system-biological approach for the causal treatment of AD, which might even be curative if the systemic intervention is initiated early enough in the disease process. Hence an individualized system-biological treatment of patients with early AD is proposed as a test for the validity of UTAD and outlined in this review.
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Affiliation(s)
- Michael Nehls
- Independent Researcher, Allmendweg 1, 79279 Vörstetten, Germany
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104
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Drew LJ, Kheirbek MA, Luna VM, Denny CA, Cloidt MA, Wu MV, Jain S, Scharfman HE, Hen R. Activation of local inhibitory circuits in the dentate gyrus by adult-born neurons. Hippocampus 2016; 26:763-78. [PMID: 26662922 PMCID: PMC4867135 DOI: 10.1002/hipo.22557] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2015] [Indexed: 12/12/2022]
Abstract
Robust incorporation of new principal cells into pre-existing circuitry in the adult mammalian brain is unique to the hippocampal dentate gyrus (DG). We asked if adult-born granule cells (GCs) might act to regulate processing within the DG by modulating the substantially more abundant mature GCs. Optogenetic stimulation of a cohort of young adult-born GCs (0 to 7 weeks post-mitosis) revealed that these cells activate local GABAergic interneurons to evoke strong inhibitory input to mature GCs. Natural manipulation of neurogenesis by aging-to decrease it-and housing in an enriched environment-to increase it-strongly affected the levels of inhibition. We also demonstrated that elevating activity in adult-born GCs in awake behaving animals reduced the overall number of mature GCs activated by exploration. These data suggest that inhibitory modulation of mature GCs may be an important function of adult-born hippocampal neurons. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Liam J. Drew
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Mazen A. Kheirbek
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Department of Neuroscience, Columbia University, New York, NY 10032, USA
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Victor M. Luna
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Christine A. Denny
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Megan A. Cloidt
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Melody V. Wu
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Swati Jain
- Center for Dementia Research, Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA
| | - Helen E. Scharfman
- Center for Dementia Research, Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA
- Departments of Child and Adolescent Psychiatry, Physiology and Neuroscience, and Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA
| | - René Hen
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Department of Neuroscience, Columbia University, New York, NY 10032, USA
- Department of Pharmacology, Columbia University, New York, NY 10032, USA
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
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105
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Tannenholz L, Hen R, Kheirbek MA. GluN2B-Containg NMDA Receptors on Adult-Born Granule Cells Contribute to the Antidepressant Action of Fluoxetine. Front Neurosci 2016; 10:242. [PMID: 27303260 PMCID: PMC4885883 DOI: 10.3389/fnins.2016.00242] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 05/17/2016] [Indexed: 01/09/2023] Open
Abstract
Ablation of adult neurogenesis in mice has revealed that young adult-born granule cells (abGCs) are required for some of the behavioral responses to antidepressants (ADs), yet the mechanism by which abGCs contribute to AD action remains unknown. During their maturation process, these immature neurons exhibit unique properties that could underlie their ability to influence behavioral output. In particular, abGCs in the DG exhibit a period of heightened plasticity 4–6 weeks after birth that is mediated by GluN2B-expressing NMDA receptors. The functional contribution of this critical window to AD responsiveness is unclear. Here, we determined the behavioral and neurogenic responses to the AD fluoxetine (FLX) in mice lacking GluN2B-containing NMDA receptors in abGCs. We found that these mice exhibited an attenuated response to FLX in a neurogenesis-dependent behavioral assay of FLX action, while neurogenesis-independent behaviors were unaffected by GluN2B deletion. In addition, deletion of GluN2B attenuated FLX-induced increases in dendritic complexity of abGCs suggesting that the blunted behavioral efficacy of FLX may be caused by impaired differentiation of young abGCs.
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Affiliation(s)
- Lindsay Tannenholz
- Department of Pharmacology, Columbia UniversityNew York, NY, USA; Division of Integrative Neuroscience, New York State Psychiatric InstituteNew York, NY, USA
| | - René Hen
- Department of Pharmacology, Columbia UniversityNew York, NY, USA; Division of Integrative Neuroscience, New York State Psychiatric InstituteNew York, NY, USA; Department of Psychiatry, Columbia UniversityNew York, NY, USA; Department of Neuroscience, Columbia UniversityNew York, NY, USA
| | - Mazen A Kheirbek
- Division of Integrative Neuroscience, New York State Psychiatric InstituteNew York, NY, USA; Department of Psychiatry, Columbia UniversityNew York, NY, USA; Department of Psychiatry, University of CaliforniaSan Francisco, CA, USA
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106
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Poo MM, Pignatelli M, Ryan TJ, Tonegawa S, Bonhoeffer T, Martin KC, Rudenko A, Tsai LH, Tsien RW, Fishell G, Mullins C, Gonçalves JT, Shtrahman M, Johnston ST, Gage FH, Dan Y, Long J, Buzsáki G, Stevens C. What is memory? The present state of the engram. BMC Biol 2016; 14:40. [PMID: 27197636 PMCID: PMC4874022 DOI: 10.1186/s12915-016-0261-6] [Citation(s) in RCA: 208] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The mechanism of memory remains one of the great unsolved problems of biology. Grappling with the question more than a hundred years ago, the German zoologist Richard Semon formulated the concept of the engram, lasting connections in the brain that result from simultaneous “excitations”, whose precise physical nature and consequences were out of reach of the biology of his day. Neuroscientists now have the knowledge and tools to tackle this question, however, and this Forum brings together leading contemporary views on the mechanisms of memory and what the engram means today.
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Affiliation(s)
- Mu-Ming Poo
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China.
| | - Michele Pignatelli
- RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Tomás J Ryan
- RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Susumu Tonegawa
- RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | | | - Kelsey C Martin
- Department of Biological Chemistry and Department of Psychiatry and Biobehavioral Studies, David Geffen School of Medicine, BSRB 390B, 615 Charles E. Young Dr. South, University of California, Los Angeles, CA, 90095, USA
| | - Andrii Rudenko
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Li-Huei Tsai
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Richard W Tsien
- The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, NY, 10016, USA
| | - Gord Fishell
- The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, NY, 10016, USA
| | - Caitlin Mullins
- The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, NY, 10016, USA
| | - J Tiago Gonçalves
- Salk Institute for Biological Studies, Laboratory of Genetics, 10010 N. Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Matthew Shtrahman
- Salk Institute for Biological Studies, Laboratory of Genetics, 10010 N. Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Stephen T Johnston
- Salk Institute for Biological Studies, Laboratory of Genetics, 10010 N. Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Fred H Gage
- Salk Institute for Biological Studies, Laboratory of Genetics, 10010 N. Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Yang Dan
- HHMI, Department of Molecular and Cell Biology, University of California, Berkeley, USA
| | - John Long
- The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, NY, 10016, USA
| | - György Buzsáki
- The Neuroscience Institute, School of Medicine and Center for Neural Science, New York University, New York, NY, 10016, USA
| | - Charles Stevens
- Salk Institute for Biological Studies, Laboratory of Genetics, 10010 N. Torrey Pines Road, La Jolla, CA, 92037, USA
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107
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Castilla-Ortega E, Serrano A, Blanco E, Araos P, Suárez J, Pavón FJ, Rodríguez de Fonseca F, Santín LJ. A place for the hippocampus in the cocaine addiction circuit: Potential roles for adult hippocampal neurogenesis. Neurosci Biobehav Rev 2016; 66:15-32. [PMID: 27118134 DOI: 10.1016/j.neubiorev.2016.03.030] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 03/08/2016] [Accepted: 03/08/2016] [Indexed: 02/07/2023]
Abstract
Cocaine addiction is a chronic brain disease in which the drug seeking habits and profound cognitive, emotional and motivational alterations emerge from drug-induced neuroadaptations on a vulnerable brain. Therefore, a 'cocaine addiction brain circuit' has been described to explain this disorder. Studies in both cocaine patients and rodents reveal the hippocampus as a main node in the cocaine addiction circuit. The contribution of the hippocampus to cocaine craving and the associated memories is essential to understand the chronic relapsing nature of addiction, which is the main obstacle for the recovery. Interestingly, the hippocampus holds a particular form of plasticity that is rare in the adult brain: the ability to generate new functional neurons. There is an active scientific debate on the contributions of these new neurons to the addicted brain. This review focuses on the potential role(s) of adult hippocampal neurogenesis (AHN) in cocaine addiction. Although the current evidence primarily originates from animal research, these preclinical studies support AHN as a relevant component for the hippocampal effects of cocaine.
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Affiliation(s)
- Estela Castilla-Ortega
- Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain.
| | - Antonia Serrano
- Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Eduardo Blanco
- Departament de Pedagogia i Psicologia, Facultat d'Educació, Psicologia i Treball Social, Universitat de Lleida, Spain
| | - Pedro Araos
- Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Juan Suárez
- Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Francisco J Pavón
- Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Fernando Rodríguez de Fonseca
- Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Luis J Santín
- Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Instituto de Investigación Biomédica de Málaga (IBIMA), Facultad de Psicología, Universidad de Málaga, Spain.
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108
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Danielson NB, Kaifosh P, Zaremba JD, Lovett-Barron M, Tsai J, Denny CA, Balough EM, Goldberg AR, Drew LJ, Hen R, Losonczy A, Kheirbek MA. Distinct Contribution of Adult-Born Hippocampal Granule Cells to Context Encoding. Neuron 2016; 90:101-12. [PMID: 26971949 PMCID: PMC4962695 DOI: 10.1016/j.neuron.2016.02.019] [Citation(s) in RCA: 236] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 01/29/2016] [Accepted: 02/10/2016] [Indexed: 12/21/2022]
Abstract
Adult-born granule cells (abGCs) have been implicated in cognition and mood; however, it remains unknown how these cells behave in vivo. Here, we have used two-photon calcium imaging to monitor the activity of young abGCs in awake behaving mice. We find that young adult-born neurons fire at a higher rate in vivo but paradoxically exhibit less spatial tuning than their mature counterparts. When presented with different contexts, mature granule cells underwent robust remapping of their spatial representations, and the few spatially tuned adult-born cells remapped to a similar degree. We next used optogenetic silencing to confirm the direct involvement of abGCs in context encoding and discrimination, consistent with their proposed role in pattern separation. These results provide the first in vivo characterization of abGCs and reveal their participation in the encoding of novel information.
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Affiliation(s)
- Nathan B Danielson
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | - Patrick Kaifosh
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | - Jeffrey D Zaremba
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | - Matthew Lovett-Barron
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Joseph Tsai
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | - Christine A Denny
- Department of Psychiatry, Columbia University, New York, NY 10032, USA; Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Elizabeth M Balough
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | - Alexander R Goldberg
- Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Liam J Drew
- Department of Psychiatry, Columbia University, New York, NY 10032, USA; Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA; Wolfson Institute for Biomedical Research, UCL, London WC1E 0BT, UK
| | - René Hen
- Department of Psychiatry, Columbia University, New York, NY 10032, USA; Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA; Department of Neuroscience, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA
| | - Attila Losonczy
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA.
| | - Mazen A Kheirbek
- Department of Psychiatry, Columbia University, New York, NY 10032, USA; Division of Integrative Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA; Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA; Center for Integrative Neuroscience, University of California, San Francisco, San Francisco, CA 94158, USA
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109
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110
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Tonic Inhibitory Control of Dentate Gyrus Granule Cells by α5-Containing GABAA Receptors Reduces Memory Interference. J Neurosci 2016; 35:13698-712. [PMID: 26446222 DOI: 10.1523/jneurosci.1370-15.2015] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Interference between similar or overlapping memories formed at different times poses an important challenge on the hippocampal declarative memory system. Difficulties in managing interference are at the core of disabling cognitive deficits in neuropsychiatric disorders. Computational models have suggested that, in the normal brain, the sparse activation of the dentate gyrus granule cells maintained by tonic inhibitory control enables pattern separation, an orthogonalization process that allows distinct representations of memories despite interference. To test this mechanistic hypothesis, we generated mice with significantly reduced expression of the α5-containing GABAA (α5-GABAARs) receptors selectively in the granule cells of the dentate gyrus (α5DGKO mice). α5DGKO mice had reduced tonic inhibition of the granule cells without any change in fast phasic inhibition and showed increased activation in the dentate gyrus when presented with novel stimuli. α5DGKO mice showed impairments in cognitive tasks characterized by high interference, without any deficiencies in low-interference tasks, suggesting specific impairment of pattern separation. Reduction of fast phasic inhibition in the dentate gyrus through granule cell-selective knock-out of α2-GABAARs or the knock-out of the α5-GABAARs in the downstream CA3 area did not detract from pattern separation abilities, which confirms the anatomical and molecular specificity of the findings. In addition to lending empirical support to computational hypotheses, our findings have implications for the treatment of interference-related cognitive symptoms in neuropsychiatric disorders, particularly considering the availability of pharmacological agents selectively targeting α5-GABAARs. SIGNIFICANCE STATEMENT Interference between similar memories poses a significant limitation on the hippocampal declarative memory system, and impaired interference management is a cognitive symptom in many disorders. Thus, understanding mechanisms of successful interference management or processes that can lead to interference-related memory problems has high theoretical and translational importance. This study provides empirical evidence that tonic inhibition in the dentate gyrus (DG), which maintains sparseness of neuronal activation in the DG, is essential for management of interference. The specificity of findings to tonic, but not faster, more transient types of neuronal inhibition and to the DG, but not the neighboring brain areas, is presented through control experiments. Thus, the findings link interference management to a specific mechanism, proposed previously by computational models.
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111
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Adult Hippocampal Neurogenesis, Fear Generalization, and Stress. Neuropsychopharmacology 2016; 41:24-44. [PMID: 26068726 PMCID: PMC4677119 DOI: 10.1038/npp.2015.167] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/29/2015] [Accepted: 06/05/2015] [Indexed: 12/21/2022]
Abstract
The generalization of fear is an adaptive, behavioral, and physiological response to the likelihood of threat in the environment. In contrast, the overgeneralization of fear, a cardinal feature of posttraumatic stress disorder (PTSD), manifests as inappropriate, uncontrollable expression of fear in neutral and safe environments. Overgeneralization of fear stems from impaired discrimination of safe from aversive environments or discernment of unlikely threats from those that are highly probable. In addition, the time-dependent erosion of episodic details of traumatic memories might contribute to their generalization. Understanding the neural mechanisms underlying the overgeneralization of fear will guide development of novel therapeutic strategies to combat PTSD. Here, we conceptualize generalization of fear in terms of resolution of interference between similar memories. We propose a role for a fundamental encoding mechanism, pattern separation, in the dentate gyrus (DG)-CA3 circuit in resolving interference between ambiguous or uncertain threats and in preserving episodic content of remote aversive memories in hippocampal-cortical networks. We invoke cellular-, circuit-, and systems-based mechanisms by which adult-born dentate granule cells (DGCs) modulate pattern separation to influence resolution of interference and maintain precision of remote aversive memories. We discuss evidence for how these mechanisms are affected by stress, a risk factor for PTSD, to increase memory interference and decrease precision. Using this scaffold we ideate strategies to curb overgeneralization of fear in PTSD.
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112
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Johnston ST, Shtrahman M, Parylak S, Gonçalves JT, Gage FH. Paradox of pattern separation and adult neurogenesis: A dual role for new neurons balancing memory resolution and robustness. Neurobiol Learn Mem 2015; 129:60-8. [PMID: 26549627 DOI: 10.1016/j.nlm.2015.10.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 10/22/2015] [Accepted: 10/27/2015] [Indexed: 01/31/2023]
Abstract
Hippocampal adult neurogenesis is thought to subserve pattern separation, the process by which similar patterns of neuronal inputs are transformed into distinct neuronal representations, permitting the discrimination of highly similar stimuli in hippocampus-dependent tasks. However, the mechanism by which immature adult-born dentate granule neurons cells (abDGCs) perform this function remains unknown. Two theories of abDGC function, one by which abDGCs modulate and sparsify activity in the dentate gyrus and one by which abDGCs act as autonomous coding units, are generally suggested to be mutually exclusive. This review suggests that these two mechanisms work in tandem to dynamically regulate memory resolution while avoiding memory interference and maintaining memory robustness.
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Affiliation(s)
- Stephen T Johnston
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - Matthew Shtrahman
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - Sarah Parylak
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - J Tiago Gonçalves
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States
| | - Fred H Gage
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, United States.
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113
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Abstract
UNLABELLED Behavioral studies have established a role for adult-born dentate granule cells in discriminating between similar memories. However, it is unclear how these cells mediate memory discrimination. Excitability is enhanced in maturing adult-born neurons, spurring the hypothesis that the activity of these cells "directly" encodes and stores memories. An alternative hypothesis posits that maturing neurons "indirectly" contribute to memory encoding by regulating excitation-inhibition balance. We evaluated these alternatives by using dentate-sensitive active place avoidance tasks to assess experience-dependent changes in dentate field potentials in the presence and absence of neurogenesis. Before training, X-ray ablation of adult neurogenesis-reduced dentate responses to perforant-path stimulation and shifted EPSP-spike coupling leftward. These differences were unchanged after place avoidance training with the shock zone in the initial location, which both groups learned to avoid equally well. In contrast, sham-treated mice decreased dentate responses and shifted EPSP-spike coupling leftward after the shock zone was relocated, whereas X-irradiated mice failed to show these changes in dentate function and were impaired on this test of memory discrimination. During place avoidance, excitation-inhibition coupled neural synchrony in dentate local field potentials was reduced in X-irradiated mice, especially in the θ band. The difference was most prominent during conflict learning, which is impaired in the X-irradiated mice. These findings indicate that maturing adult-born neurons regulate both functional network plasticity in response to memory discrimination and dentate excitation-inhibition coordination. The most parsimonious interpretation of these results is that adult neurogenesis indirectly regulates hippocampal information processing. SIGNIFICANCE STATEMENT Adult-born neurons in the hippocampal dentate gyrus are important for flexibly using memories, but the mechanism is controversial. Using tests of hippocampus-dependent place avoidance learning and dentate electrophysiology in mice with normal or ablated neurogenesis, we find that maturing adult-born neurons are crucial only when memory must be used flexibly, and that these neurons regulate dentate gyrus synaptic and spiking responses to neocortical input rather than directly storing information, as has been proposed. A day after learning to avoid the initial or changed locations of shock, the dentate synaptic responses are enhanced or suppressed, respectively, unlike mice lacking adult neurogenesis, which did not change. The contribution of adult neurogenesis to memory is indirect, by regulating dentate excitation-inhibition coupling.
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114
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Development of Adult-Generated Cell Connectivity with Excitatory and Inhibitory Cell Populations in the Hippocampus. J Neurosci 2015. [PMID: 26203153 DOI: 10.1523/jneurosci.3238-14.2015] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
New neurons are generated continuously in the subgranular zone of the hippocampus and integrate into existing hippocampal circuits throughout adulthood. Although the addition of these new neurons may facilitate the formation of new memories, as they integrate, they provide additional excitatory drive to CA3 pyramidal neurons. During development, to maintain homeostasis, new neurons form preferential contacts with local inhibitory circuits. Using retroviral and transgenic approaches to label adult-generated granule cells, we first asked whether a comparable process occurs in the adult hippocampus in mice. Similar to development, we found that, during adulthood, new neurons form connections with inhibitory cells in the dentate gyrus, hilus, and CA3 regions as they integrate into hippocampal circuits. In particular, en passant bouton and filopodia connections with CA3 interneurons peak when adult-generated dentate granule cells (DGCs) are ∼4 weeks of age, a time point when these cells are most excitable. Consistent with this, optical stimulation of 4-week-old (but not 6- or 8-week-old) adult-generated DGCs strongly activated CA3 interneurons. Finally, we found that CA3 interneurons were activated robustly during learning and that their activity was strongly coupled with activity of 4-week-old (but not older) adult-generated DGCs. These data indicate that, as adult-generated neurons integrate into hippocampal circuits, they transiently form strong anatomical, effective, and functional connections with local inhibitory circuits in CA3. Significance statement: New neurons are generated continuously in the subgranular zone of the hippocampus and integrate into existing hippocampal circuits throughout adulthood. Understanding how these cells integrate within well formed circuits will increase our knowledge about the basic principles governing circuit assembly in the adult hippocampus. This study uses a combined connectivity analysis (anatomical, functional, and effective) of the output connections of adult-born hippocampal cells to show that, as these cells integrate into hippocampal circuits, they transiently form strong connections with local inhibitory circuits. This transient increase of connectivity may represent an homeostatic process necessary to accommodate changes in the excitation/inhibition balance induced by the addition of these new excitatory cells to the preexisting excitatory hippocampal circuits.
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115
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Samuels BA, Anacker C, Hu A, Levinstein MR, Pickenhagen A, Tsetsenis T, Madroñal N, Donaldson ZR, Drew LJ, Dranovsky A, Gross CT, Tanaka KF, Hen R. 5-HT1A receptors on mature dentate gyrus granule cells are critical for the antidepressant response. Nat Neurosci 2015; 18:1606-16. [PMID: 26389840 PMCID: PMC4624493 DOI: 10.1038/nn.4116] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 08/19/2015] [Indexed: 12/11/2022]
Abstract
Selective serotonin reuptake inhibitors (SSRIs) are widely used antidepressants, but the mechanisms by which they influence behavior are only partially resolved. Adult hippocampal neurogenesis is necessary for some of the responses to SSRIs, but it is unknown whether the mature dentate gyrus granule cells (mature DG GCs) also contribute. We deleted Serotonin 1A receptor (5HT1AR; a receptor required for the SSRI response) specifically from DG GCs and found that the effects of the SSRI fluoxetine on behavior and the Hypothalamic-Pituitary-Adrenal (HPA) axis were abolished. By contrast, mice lacking 5HT1ARs only in young adult born granule cells (abGCs) showed normal fluoxetine responses. Importantly, 5HT1AR deficient mice engineered to express functional 5HT1ARs only in DG GCs responded to fluoxetine, indicating that 5HT1ARs in DG GCs are sufficient to mediate an antidepressant response. Taken together, these data indicate that both mature DG GCs and young abGCs must be engaged for an antidepressant response.
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Affiliation(s)
- Benjamin Adam Samuels
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Christoph Anacker
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Alice Hu
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Marjorie R Levinstein
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Anouchka Pickenhagen
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Theodore Tsetsenis
- Mouse Biology Unit, European Molecular Biology Laboratory (EMBL), Monterotondo, Italy
| | - Noelia Madroñal
- Mouse Biology Unit, European Molecular Biology Laboratory (EMBL), Monterotondo, Italy
| | - Zoe R Donaldson
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Liam John Drew
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Alex Dranovsky
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
| | - Cornelius T Gross
- Mouse Biology Unit, European Molecular Biology Laboratory (EMBL), Monterotondo, Italy
| | - Kenji F Tanaka
- Department of Neuropsychiatry, School of Medicine, Keio University, Tokyo, Japan
| | - René Hen
- Department of Psychiatry, Columbia University Medical Center and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, New York, USA
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116
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Anacker C, Denny CA, Hen R. Regulation of hippocampal memory traces by neurogenesis. NEUROGENESIS 2015; 2:e1025180. [PMID: 27604158 PMCID: PMC4973587 DOI: 10.1080/23262133.2015.1025180] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/24/2015] [Accepted: 02/25/2015] [Indexed: 12/27/2022]
Abstract
The hippocampus has long been known as a brain structure fundamental for memory formation and retrieval. Recent technological advances of cellular tracing techniques and optogenetic manipulation strategies have allowed to unravel important aspects of the cellular origin of memory, and have started to shed new light on the neuronal networks involved in encoding, consolidation and retrieval of memory in the hippocampus. In particular, memory traces, or engrams, that are formed during encoding in the dentate gyrus and CA3 region are crucial for memory retrieval and amenable to modulation by neuroplastic mechanisms, including adult hippocampal neurogenesis. Here, we will discuss how memory traces are being encoded at the cellular level, how they may contribute to pattern separation and pattern completion in the hippocampus, and how they can be associated with different experiences to express memories of opposite valence. We propose a mechanism by which adult hippocampal neurogenesis may contribute to the formation of engrams, which may be relevant not only for the encoding of contextual information, but also for mood abnormalities, such as anxiety and depression.
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Affiliation(s)
- Christoph Anacker
- Department of Psychiatry; Columbia University; New York, NY USA; Division of Integrative Neuroscience, New York State Psychiatric Institute/Research Foundation for Mental Hygiene; Inc. ; New York, NY USA
| | - Christine Ann Denny
- Department of Psychiatry; Columbia University; New York, NY USA; Division of Integrative Neuroscience, New York State Psychiatric Institute/Research Foundation for Mental Hygiene; Inc. ; New York, NY USA
| | - René Hen
- Department of Neuroscience; Columbia University; New York, NY USA; Department of Pharmacology; Columbia University; New York, NY USA; Department of Psychiatry; Columbia University; New York, NY USA; Division of Integrative Neuroscience; New York State Psychiatric Institute ; New York, NY USA
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117
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McAvoy K, Besnard A, Sahay A. Adult hippocampal neurogenesis and pattern separation in DG: a role for feedback inhibition in modulating sparseness to govern population-based coding. Front Syst Neurosci 2015; 9:120. [PMID: 26347621 PMCID: PMC4542503 DOI: 10.3389/fnsys.2015.00120] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 08/07/2015] [Indexed: 12/17/2022] Open
Abstract
The dentate gyrus (DG) of mammals harbors neural stem cells that generate new dentate granule cells (DGCs) throughout life. Behavioral studies using the contextual fear discrimination paradigm have found that selectively augmenting or blocking adult hippocampal neurogenesis enhances or impairs discrimination under conditions of high, but not low, interference suggestive of a role in pattern separation. Although contextual discrimination engages population-based coding mechanisms underlying pattern separation such as global remapping in the DG and CA3, how adult hippocampal neurogenesis modulates pattern separation in the DG is poorly understood. Here, we propose a role for adult-born DGCs in re-activation coupled modulation of sparseness through feed-back inhibition to govern global remapping in the DG.
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Affiliation(s)
- Kathleen McAvoy
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
| | - Antoine Besnard
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA ; Harvard Stem Cell Institute, Harvard University Cambridge, MA, USA ; Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
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118
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Scharfman HE, Bernstein HL. Potential implications of a monosynaptic pathway from mossy cells to adult-born granule cells of the dentate gyrus. Front Syst Neurosci 2015; 9:112. [PMID: 26347618 PMCID: PMC4541026 DOI: 10.3389/fnsys.2015.00112] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 07/20/2015] [Indexed: 11/13/2022] Open
Abstract
The dentate gyrus (DG) is important to many aspects of hippocampal function, but there are many aspects of the DG that are incompletely understood. One example is the role of mossy cells (MCs), a major DG cell type that is glutamatergic and innervates the primary output cells of the DG, the granule cells (GCs). MCs innervate the GCs as well as local circuit neurons that make GABAergic synapses on GCs, so the net effect of MCs on GCs – and therefore the output of the DG – is unclear. Here we first review fundamental information about MCs and the current hypotheses for their role in the normal DG and in diseases that involve the DG. Then we review previously published data which suggest that MCs are a source of input to a subset of GCs that are born in adulthood (adult-born GCs). In addition, we discuss the evidence that adult-born GCs may support the normal inhibitory ‘gate’ functions of the DG, where the GCs are a filter or gate for information from the entorhinal cortical input to area CA3. The implications are then discussed in the context of seizures and temporal lobe epilepsy (TLE). In TLE, it has been suggested that the DG inhibitory gate is weak or broken and MC loss leads to insufficient activation of inhibitory neurons, causing hyperexcitability. That idea was called the “dormant basket cell hypothesis.” Recent data suggest that loss of normal adult-born GCs may also cause disinhibition, and seizure susceptibility. Therefore, we propose a reconsideration of the dormant basket cell hypothesis with an intervening adult-born GC between the MC and basket cell and call this hypothesis the “dormant immature granule cell hypothesis.”
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Affiliation(s)
- Helen E Scharfman
- The Nathan Kline Institute for Psychiatric Research, Orangeburg NY, USA ; New York University Langone Medical Center, New York NY, USA
| | - Hannah L Bernstein
- The Nathan Kline Institute for Psychiatric Research, Orangeburg NY, USA ; New York University Langone Medical Center, New York NY, USA
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119
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Pardi MB, Ogando MB, Schinder AF, Marin-Burgin A. Differential inhibition onto developing and mature granule cells generates high-frequency filters with variable gain. eLife 2015; 4:e08764. [PMID: 26163657 PMCID: PMC4521582 DOI: 10.7554/elife.08764] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Accepted: 07/10/2015] [Indexed: 11/13/2022] Open
Abstract
Adult hippocampal neurogenesis provides the dentate gyrus with heterogeneous populations of granule cells (GC) originated at different times. The contribution of these cells to information encoding is under current investigation. Here, we show that incoming spike trains activate different populations of GC determined by the stimulation frequency and GC age. Immature GC respond to a wider range of stimulus frequencies, whereas mature GC are less responsive at high frequencies. This difference is dictated by feedforward inhibition, which restricts mature GC activation. Yet, the stronger inhibition of mature GC results in a higher temporal fidelity compared to that of immature GC. Thus, hippocampal inputs activate two populations of neurons with variable frequency filters: immature cells, with wide-range responses, that are reliable transmitters of the incoming frequency, and mature neurons, with narrow frequency response, that are precise at informing the beginning of the stimulus, but with a sparse activity.
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Affiliation(s)
- María Belén Pardi
- Instituto de Investigación en Biomedicina de Buenos Aires-CONICET-Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Mora Belén Ogando
- Instituto de Investigación en Biomedicina de Buenos Aires-CONICET-Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Alejandro F Schinder
- Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Buenos Aires, Argentina
| | - Antonia Marin-Burgin
- Instituto de Investigación en Biomedicina de Buenos Aires-CONICET-Partner Institute of the Max Planck Society, Buenos Aires, Argentina
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120
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Zanni G, Zhou K, Riebe I, Xie C, Zhu C, Hanse E, Blomgren K. Irradiation of the Juvenile Brain Provokes a Shift from Long-Term Potentiation to Long-Term Depression. Dev Neurosci 2015; 37:263-72. [PMID: 26043717 DOI: 10.1159/000430435] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/11/2015] [Indexed: 11/19/2022] Open
Abstract
Radiotherapy is common in the treatment of brain tumors in children but often causes deleterious, late-appearing sequelae, including cognitive decline. This is thought to be caused, at least partly, by the suppression of hippocampal neurogenesis. However, the changes in neuronal network properties in the dentate gyrus (DG) following the irradiation of the young, growing brain are still poorly understood. We characterized the long-lasting effects of irradiation on the electrophysiological properties of the DG after a single dose of 6-Gy whole-brain irradiation on postnatal day 11 in male Wistar rats. The assessment of the basal excitatory transmission in the medial perforant pathway (MPP) by an examination of the field excitatory postsynaptic potential/volley ratio showed an increase of the synaptic efficacy per axon in irradiated animals compared to sham controls. The paired-pulse ratio at the MPP granule cell synapses was not affected by irradiation, suggesting that the release probability of neurotransmitters was not altered. Surprisingly, the induction of long-term synaptic plasticity in the DG by applying 4 trains of high-frequency stimulation provoked a shift from long-term potentiation (LTP) to long-term depression (LTD) in irradiated animals compared to sham controls. The morphological changes consisted in a virtually complete ablation of neurogenesis following irradiation, as judged by doublecortin immunostaining, while the inhibitory network of parvalbumin interneurons was intact. These data suggest that the irradiation of the juvenile brain caused permanent changes in synaptic plasticity that would seem consistent with an impairment of declarative learning. Unlike in our previous study in mice, lithium treatment did unfortunately not ameliorate any of the studied parameters. For the first time, we show that the effects of cranial irradiation on long-term synaptic plasticity is different in the juvenile compared with the adult brain, such that while irradiation of the adult brain will only cause a reduction in LTP, irradiation of the juvenile brain goes further and causes LTD. Although the mechanisms underlying the synaptic alterations need to be elucidated, these findings provide a better understanding of the effects of irradiation in the developing brain and the cognitive deficits observed in young patients who have been subjected to cranial radiotherapy. © 2015 S. Karger AG, Basel.
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Affiliation(s)
- Giulia Zanni
- Center for Brain Repair and Rehabilitation, University of Gothenburg, Gothenburg, Sweden
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121
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Abrous DN, Wojtowicz JM. Interaction between Neurogenesis and Hippocampal Memory System: New Vistas. Cold Spring Harb Perspect Biol 2015; 7:7/6/a018952. [PMID: 26032718 DOI: 10.1101/cshperspect.a018952] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
During the last decade, the questions on the functionality of adult neurogenesis have changed their emphasis from if to how the adult-born neurons participate in a variety of memory processes. The emerging answers are complex because we are overwhelmed by a variety of behavioral tasks that apparently require new neurons to be performed optimally. With few exceptions, the hippocampal memory system seems to use the newly generated neurons for multiple roles. Adult neurogenesis has given the dentate gyrus new capabilities not previously thought possible within the scope of traditional synaptic plasticity. Looking at these new developments from the perspective of past discoveries, the science of adult neurogenesis has emerged from its initial phase of being, first, a surprising oddity and, later, exciting possibility, to the present state of being an integral part of mainstream neuroscience. The answers to many remaining questions regarding adult neurogenesis will come along only with our growing understanding of the functionality of the brain as a whole. This, in turn, will require integration of multiple levels of organization from molecules and cells to circuits and systems, ultimately resulting in comprehension of behavioral outcomes.
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Affiliation(s)
- Djoher Nora Abrous
- Inserm U862, Bordeaux-F33077, France Université de Bordeaux, Bordeaux-F33077, France
| | - Jan Martin Wojtowicz
- Department of Physiology, University of Toronto, Medical Sciences Building, Toronto, Ontario M5S 1A8, Canada
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122
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Imoto Y, Kira T, Sukeno M, Nishitani N, Nagayasu K, Nakagawa T, Kaneko S, Kobayashi K, Segi-Nishida E. Role of the 5-HT4 receptor in chronic fluoxetine treatment-induced neurogenic activity and granule cell dematuration in the dentate gyrus. Mol Brain 2015; 8:29. [PMID: 25976618 PMCID: PMC4430984 DOI: 10.1186/s13041-015-0120-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 04/24/2015] [Indexed: 11/30/2022] Open
Abstract
Background Chronic treatment with selective serotonin (5-HT) reuptake inhibitors (SSRIs) facilitates adult neurogenesis and reverses the state of maturation in mature granule cells (GCs) in the dentate gyrus (DG) of the hippocampus. Recent studies have suggested that the 5-HT4 receptor is involved in both effects. However, it is largely unknown how the 5-HT4 receptor mediates neurogenic effects in the DG and, how the neurogenic and dematuration effects of SSRIs interact with each other. Results We addressed these issues using 5-HT4 receptor knockout (5-HT4R KO) mice. Expression of the 5-HT4 receptor was detected in mature GCs but not in neuronal progenitors of the DG. We found that chronic treatment with the SSRI fluoxetine significantly increased cell proliferation and the number of doublecortin-positive cells in the DG of wild-type mice, but not in 5-HT4R KO mice. We then examined the correlation between the increased neurogenesis and the dematuration of GCs. As reported previously, reduced expression of calbindin in the DG, as an index of dematuration, by chronic fluoxetine treatment was observed in wild-type mice but not in 5-HT4R KO mice. The proliferative effect of fluoxetine was inversely correlated with the expression level of calbindin in the DG. The expression of neurogenic factors in the DG, such as brain derived neurotrophic factor (Bdnf), was also associated with the progression of dematuration. These results indicate that the neurogenic effects of fluoxetine in the DG are closely associated with the progression of dematuration of GCs. In contrast, the DG in which neurogenesis was impaired by irradiation still showed significant reduction of calbindin expression by chronic fluoxetine treatment, suggesting that dematuration of GCs by fluoxetine does not require adult neurogenesis in the DG. Conclusions We demonstrated that the 5-HT4 receptor plays an important role in fluoxetine-induced adult neurogenesis in the DG in addition to GC dematuration, and that these phenomena are closely associated. Our results suggest that 5-HT4 receptor-mediated phenotypic changes, including dematuration in mature GCs, underlie the neurogenic effect of SSRIs in the DG, providing new insight into the cellular mechanisms of the neurogenic actions of SSRIs in the hippocampus.
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Affiliation(s)
- Yuki Imoto
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Toshihiko Kira
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Mamiko Sukeno
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Naoya Nishitani
- Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Kazuki Nagayasu
- Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Takayuki Nakagawa
- Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Shuji Kaneko
- Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
| | - Katsunori Kobayashi
- Department of Pharmacology, Graduate School of Medicine, Nippon Medical School, Sendagi, Bunkyo-ku, Tokyo, Japan. .,Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, Saitama, 332-0012, Japan.
| | - Eri Segi-Nishida
- Department of Biological Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo, 125-8585, Japan.
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123
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Abstract
GABAergic interneurons enforce highly sparse activity patterns in principal neurons of the dentate gyrus. In this issue of Neuron, Temprana et al. (2015) show that immature adult-born neurons largely function independently of inhibitory feedback circuits, neither receiving nor generating feedback inhibition.
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124
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Stepan J, Dine J, Eder M. Functional optical probing of the hippocampal trisynaptic circuit in vitro: network dynamics, filter properties, and polysynaptic induction of CA1 LTP. Front Neurosci 2015; 9:160. [PMID: 25999809 PMCID: PMC4422028 DOI: 10.3389/fnins.2015.00160] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 04/19/2015] [Indexed: 12/21/2022] Open
Abstract
Decades of brain research have identified various parallel loops linking the hippocampus with neocortical areas, enabling the acquisition of spatial and episodic memories. Especially the hippocampal trisynaptic circuit [entorhinal cortex layer II → dentate gyrus (DG) → cornu ammonis (CA)-3 → CA1] was studied in great detail because of its seemingly simple connectivity and characteristic structures that are experimentally well accessible. While numerous researchers focused on functional aspects, obtained from a limited number of cells in distinct hippocampal subregions, little is known about the neuronal network dynamics which drive information across multiple synapses for subsequent long-term storage. Fast voltage-sensitive dye imaging in vitro allows real-time recording of activity patterns in large/meso-scale neuronal networks with high spatial resolution. In this way, we recently found that entorhinal theta-frequency input to the DG most effectively passes filter mechanisms of the trisynaptic circuit network, generating activity waves which propagate across the entire DG-CA axis. These "trisynaptic circuit waves" involve high-frequency firing of CA3 pyramidal neurons, leading to a rapid induction of classical NMDA receptor-dependent long-term potentiation (LTP) at CA3-CA1 synapses (CA1 LTP). CA1 LTP has been substantially evidenced to be essential for some forms of explicit learning in mammals. Here, we review data with particular reference to whole network-level approaches, illustrating how activity propagation can take place within the trisynaptic circuit to drive formation of CA1 LTP.
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Affiliation(s)
- Jens Stepan
- Department Stress Neurobiology and Neurogenetics, Max Planck Institute of PsychiatryMunich, Germany
| | | | - Matthias Eder
- Department Stress Neurobiology and Neurogenetics, Max Planck Institute of PsychiatryMunich, Germany
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125
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McAvoy K, Russo C, Kim S, Rankin G, Sahay A. Fluoxetine induces input-specific hippocampal dendritic spine remodeling along the septotemporal axis in adulthood and middle age. Hippocampus 2015; 25:1429-46. [PMID: 25850664 DOI: 10.1002/hipo.22464] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/01/2015] [Indexed: 12/15/2022]
Abstract
Fluoxetine, a selective serotonin-reuptake inhibitor (SSRI), is known to induce structural rearrangements and changes in synaptic transmission in hippocampal circuitry. In the adult hippocampus, structural changes include neurogenesis, dendritic, and axonal plasticity of pyramidal and dentate granule neurons, and dedifferentiation of dentate granule neurons. However, much less is known about how chronic fluoxetine affects these processes along the septotemporal axis and during the aging process. Importantly, studies documenting the effects of fluoxetine on density and distribution of spines along different dendritic segments of dentate granule neurons and CA1 pyramidal neurons along the septotemporal axis of hippocampus in adulthood and during aging are conspicuously absent. Here, we use a transgenic mouse line in which mature dentate granule neurons and CA1 pyramidal neurons are genetically labeled with green fluorescent protein (GFP) to investigate the effects of chronic fluoxetine treatment (18 mg/kg/day) on input-specific spine remodeling and mossy fiber structural plasticity in the dorsal and ventral hippocampus in adulthood and middle age. In addition, we examine levels of adult hippocampal neurogenesis, maturation state of dentate granule neurons, neuronal activity, and glutamic acid decarboxylase-67 expression in response to chronic fluoxetine in adulthood and middle age. Our studies reveal that while chronic fluoxetine fails to augment adult hippocampal neurogenesis in middle age, the middle-aged hippocampus retains high sensitivity to changes in the dentate gyrus (DG) such as dematuration, hypoactivation, and increased glutamic acid decarboxylase 67 (GAD67) expression. Interestingly, the middle-aged hippocampus shows greater sensitivity to fluoxetine-induced input-specific synaptic remodeling than the hippocampus in adulthood with the stratum-oriens of CA1 exhibiting heightened structural plasticity. The input-specific changes and circuit-level modifications in middle-age were associated with modest enhancement in contextual fear memory precision, anxiety-like behavior and antidepressant-like behavioral responses.
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Affiliation(s)
- Kathleen McAvoy
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.,Harvard Stem Cell Institute, Harvard University, Boston, Massachusetts.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Craig Russo
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.,Harvard Stem Cell Institute, Harvard University, Boston, Massachusetts.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Shannen Kim
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.,Harvard Stem Cell Institute, Harvard University, Boston, Massachusetts.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Genelle Rankin
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.,Harvard Stem Cell Institute, Harvard University, Boston, Massachusetts.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.,Harvard Stem Cell Institute, Harvard University, Boston, Massachusetts.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
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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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127
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Dow AL, Lin TV, Chartoff EH, Potter D, McPhie DL, Van’t Veer AV, Knoll AT, Lee KN, Neve RL, Patel TB, Ongur D, Cohen BM, Carlezon WA. Sprouty2 in the dorsal hippocampus regulates neurogenesis and stress responsiveness in rats. PLoS One 2015; 10:e0120693. [PMID: 25822989 PMCID: PMC4378921 DOI: 10.1371/journal.pone.0120693] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 01/26/2015] [Indexed: 11/18/2022] Open
Abstract
Both the development and relief of stress-related psychiatric conditions such as major depression (MD) and post-traumatic stress disorder (PTSD) have been linked to neuroplastic changes in the brain. One such change involves the birth of new neurons (neurogenesis), which occurs throughout adulthood within discrete areas of the mammalian brain, including the dorsal hippocampus (HIP). Stress can trigger MD and PTSD in humans, and there is considerable evidence that it can decrease HIP neurogenesis in laboratory animals. In contrast, antidepressant treatments increase HIP neurogenesis, and their efficacy is eliminated by ablation of this process. These findings have led to the working hypothesis that HIP neurogenesis serves as a biomarker of neuroplasticity and stress resistance. Here we report that local alterations in the expression of Sprouty2 (SPRY2), an intracellular inhibitor of growth factor function, produces profound effects on both HIP neurogenesis and behaviors that reflect sensitivity to stressors. Viral vector-mediated disruption of endogenous Sprouty2 function (via a dominant negative construct) within the dorsal HIP of adult rats stimulates neurogenesis and produces signs of stress resilience including enhanced extinction of conditioned fear. Conversely, viral vector-mediated elevation of SPRY2 expression intensifies the behavioral consequences of stress. Studies of these manipulations in HIP primary cultures indicate that SPRY2 negatively regulates fibroblast growth factor-2 (FGF2), which has been previously shown to produce antidepressant- and anxiolytic-like effects via actions in the HIP. Our findings strengthen the relationship between HIP plasticity and stress responsiveness, and identify a specific intracellular pathway that could be targeted to study and treat stress-related disorders.
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Affiliation(s)
- Antonia L. Dow
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Tiffany V. Lin
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Elena H. Chartoff
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - David Potter
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Donna L. McPhie
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Ashlee V. Van’t Veer
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Allison T. Knoll
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Kristen N. Lee
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Rachael L. Neve
- Viral Gene Transfer Core Facility, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Tarun B. Patel
- Department of Pharmacology, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois, United States of America
| | - Dost Ongur
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - Bruce M. Cohen
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
| | - William A. Carlezon
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts, United States of America
- * E-mail:
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128
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Rivera PD, Raghavan RK, Yun S, Latchney SE, McGovern MK, García EF, Birnbaum SG, Eisch AJ. Retrieval of morphine-associated context induces cFos in dentate gyrus neurons. Hippocampus 2015; 25:409-14. [PMID: 25424867 DOI: 10.1002/hipo.22393] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 11/12/2014] [Accepted: 11/13/2014] [Indexed: 12/31/2022]
Abstract
Addiction has been proposed to emerge from associations between the drug and the reward-associated contexts. This associative learning has a cellular correlate, as there are more cFos+ neurons in the hippocampal dentate gyrus (DG) after psychostimulant conditioned place preference (CPP) versus saline controls. However, it is unknown whether morphine CPP leads to a similar DG activation, or whether DG activation is due to locomotion, handling, pharmacological effects, or-as data from contextual fear learning suggests-exposure to the drug-associated context. To explore this, we employed an unbiased, counterbalanced, and shortened CPP design that led to place preference and more DG cFos+ cells. Next, mice underwent morphine CPP but were then sequestered into the morphine-paired (conditioned stimulus+ [CS+]) or saline-paired (CS-) context on test day. Morphine-paired mice sequestered to CS+ had ∼30% more DG cFos+ cells than saline-paired mice. Furthermore, Bregma analysis revealed morphine-paired mice had more cFos+ cells in CS+ compared to CS- controls. Notably, there was no significant difference in DG cFos+ cell number after handling alone or after receiving morphine in home cage. Thus, retrieval of morphine-associated context is accompanied by activation of hippocampal DG granule cell neurons.
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Affiliation(s)
- Phillip D Rivera
- Department of Psychiatry, UT Southwestern Medical Center, Dallas, Texas
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Staples MC, Kim A, Mandyam CD. Dendritic remodeling of hippocampal neurons is associated with altered NMDA receptor expression in alcohol dependent rats. Mol Cell Neurosci 2015; 65:153-62. [PMID: 25769285 PMCID: PMC4395499 DOI: 10.1016/j.mcn.2015.03.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 01/17/2015] [Accepted: 03/07/2015] [Indexed: 01/01/2023] Open
Abstract
Prolonged alcohol exposure has been previously shown to impair the structure and function of the hippocampus, although the underlying structural and biochemical alterations contributing to these deleterious effects are unclear. Also unclear is whether these changes persist into prolonged periods of abstinence. Previous work from our lab utilizing a clinically relevant rodent model of alcohol consumption demonstrated that alcohol dependence (induced by chronic intermittent ethanol vapor exposure or CIE) decreases proliferation and survival of neural stem cells in the hippocampal subgranular zone and hippocampal neurogenesis in the dentate gyrus, implicating this region of the cortex as particularly sensitive to the toxic effects of prolonged ethanol exposure. For this study, we investigated seven weeks of CIE-induced morphological changes (dendritic complexity and dendritic spine density) of dentate gyrus (DG) granule cell neurons, CA3, and CA1 pyramidal neurons and the associated alterations in biochemical markers of synaptic plasticity and toxicity (NMDA receptors and PSD-95) in the hippocampus in ethanol-experienced Wistar rats 3h (CIE) and 21days (protracted abstinence) after the last ethanol vapor exposure. CIE reduced dendritic arborization of DG neurons and this effect persisted into protracted abstinence. CIE enhanced dendritic arborization of pyramidal neurons and this effect did not persist into protracted abstinence. The architectural changes in dendrites did not correlate with alterations in dendritic spine density, however, they were associated with increases in the expression of pNR2B, total NR2B, and total NR2A immediately following CIE with expression levels returning to control levels in prolonged abstinence. Overall, these data provide the evidence that CIE produces profound changes in hippocampal structural plasticity and in molecular tools that maintain hippocampal structural plasticity, and these alterations may underlie cognitive dysfunction associated with alcohol dependence. In addition, the compensatory state concurrent with reduced plasticity during protracted abstinence could leave the hippocampus vulnerable to subsequent insult following chronic ethanol exposure.
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Affiliation(s)
- Miranda C Staples
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 North Torrey Pines Road, SP30-2400, La Jolla, CA 92037, USA
| | - Airee Kim
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 North Torrey Pines Road, SP30-2400, La Jolla, CA 92037, USA
| | - Chitra D Mandyam
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 North Torrey Pines Road, SP30-2400, La Jolla, CA 92037, USA.
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130
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Iyengar SS, LaFrancois JJ, Friedman D, Drew LJ, Denny CA, Burghardt NS, Wu MV, Hsieh J, Hen R, Scharfman HE. Suppression of adult neurogenesis increases the acute effects of kainic acid. Exp Neurol 2015; 264:135-49. [PMID: 25476494 PMCID: PMC4800819 DOI: 10.1016/j.expneurol.2014.11.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 11/10/2014] [Accepted: 11/20/2014] [Indexed: 01/17/2023]
Abstract
Adult neurogenesis, the generation of new neurons in the adult brain, occurs in the hippocampal dentate gyrus (DG) and the olfactory bulb (OB) of all mammals, but the functions of these new neurons are not entirely clear. Originally, adult-born neurons were considered to have excitatory effects on the DG network, but recent studies suggest a net inhibitory effect. Therefore, we hypothesized that selective removal of newborn neurons would lead to increased susceptibility to the effects of a convulsant. This hypothesis was tested by evaluating the response to the chemoconvulsant kainic acid (KA) in mice with reduced adult neurogenesis, produced either by focal X-irradiation of the DG, or by pharmacogenetic deletion of dividing radial glial precursors. In the first 4 hrs after KA administration, when mice have the most robust seizures, mice with reduced adult neurogenesis had more severe convulsive seizures, exhibited either as a decreased latency to the first convulsive seizure, greater number of convulsive seizures, or longer convulsive seizures. Nonconvulsive seizures did not appear to change or they decreased. Four-21 hrs after KA injection, mice with reduced adult neurogenesis showed more interictal spikes (IIS) and delayed seizures than controls. Effects were greater when the anticonvulsant ethosuximide was injected 30 min prior to KA administration; ethosuximide allows forebrain seizure activity to be more easily examined in mice by suppressing seizures dominated by the brainstem. These data support the hypothesis that reduction of adult-born neurons increases the susceptibility of the brain to effects of KA.
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Affiliation(s)
- Sloka S Iyengar
- Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962
| | - John J LaFrancois
- Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962
| | - Daniel Friedman
- Department of Neurology, New York University Langone Medical Center, New York, NY 10016
| | - Liam J Drew
- WIBR, University College of London, London, UK WC1E 6BT
| | - Christine A Denny
- Department of Psychiatry, Columbia University, College of Physicians and Surgeons, New York, NY 10032
| | - Nesha S Burghardt
- Department of Psychology, Hunter College, City University of New York, New York, NY 10065
| | - Melody V Wu
- Department of Psychiatry, Columbia University, College of Physicians and Surgeons, New York, NY 10032
| | - Jenny Hsieh
- Department of Molecular Neurobiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - René Hen
- Department of Psychiatry, Columbia University, College of Physicians and Surgeons, New York, NY 10032; Department of Molecular Neurobiology, University of Texas Southwestern Medical Center, Dallas, TX 75390; New York State Psychiatric Institute, New York, NY 10032
| | - Helen E Scharfman
- Center for Dementia Research, The Nathan Kline Institute for Psychiatric Research, Orangeburg, NY 10962; Departments of Child & Adolescent Psychiatry, Physiology & Neuroscience, and Psychiatry, New York University Langone Medical Center, New York, NY 10016.
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131
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A Critical Period for Experience-Dependent Remodeling of Adult-Born Neuron Connectivity. Neuron 2015; 85:710-7. [DOI: 10.1016/j.neuron.2015.01.001] [Citation(s) in RCA: 147] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 11/16/2014] [Accepted: 12/24/2014] [Indexed: 12/12/2022]
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132
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Interleukin-17 inhibits adult hippocampal neurogenesis. Sci Rep 2014; 4:7554. [PMID: 25523081 PMCID: PMC4271266 DOI: 10.1038/srep07554] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 10/16/2014] [Indexed: 12/20/2022] Open
Abstract
Interleukin 17(A) (IL-17) is a potent pro-inflammatory cytokine that acts as a central regulator of inflammatory response within the brain, but its physiological roles under non-inflammatory conditions remain elusive. Here we report that endogenous IL-17 ablates neurogenesis in the adult dentate gyrus (DG) of hippocampus. Genetic deletion of IL-17 increased the number of adult-born neurons in the DG. Further, we found that IL-17 deletion altered cytokine network, facilitated basal excitatory synaptic transmission, enhanced intrinsic neuronal excitability, and increased expression of proneuronal genes in neuronal progenitor cells (NPCs). Our findings suggest a profound role of IL-17 in the negative regulation of adult hippocampal neurogenesis under physiology conditions.
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133
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DeCarolis NA, Rivera PD, Ahn F, Amaral WZ, LeBlanc JA, Malhotra S, Shih HY, Petrik D, Melvin N, Chen BP, Eisch AJ. 56Fe Particle Exposure Results in a Long-Lasting Increase in a Cellular Index of Genomic Instability and Transiently Suppresses Adult Hippocampal Neurogenesis in Vivo. LIFE SCIENCES IN SPACE RESEARCH 2014; 2:70-79. [PMID: 25170435 PMCID: PMC4142527 DOI: 10.1016/j.lssr.2014.06.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The high-LET HZE particles from galactic cosmic radiation pose tremendous health risks to astronauts, as they may incur sub-threshold brain injury or maladaptations that may lead to cognitive impairment. The health effects of HZE particles are difficult to predict and unfeasible to prevent. This underscores the importance of estimating radiation risks to the central nervous system as a whole as well as to specific brain regions like the hippocampus, which is central to learning and memory. Given that neurogenesis in the hippocampus has been linked to learning and memory, we investigated the response and recovery of neurogenesis and neural stem cells in the adult mouse hippocampal dentate gyrus after HZE particle exposure using two nestin transgenic reporter mouse lines to label and track radial glia stem cells (Nestin-GFP and Nestin-CreERT2/R26R:YFP mice, respectively). Mice were subjected to 56Fe particle exposure (0 or 1 Gy, at either 300 or 1000 MeV/n) and brains were harvested at early (24h), intermediate (7d), and/or long time points (2-3mo) post-irradiation. 56Fe particle exposure resulted in a robust increase in 53BP1+ foci at both the intermediate and long time points post-irradiation, suggesting long-term genomic instability in the brain. However, 56Fe particle exposure only produced a transient decrease in immature neuron number at the intermediate time point, with no significant decrease at the long time point post-irradiation. 56Fe particle exposure similarly produced a transient decrease in dividing progenitors, with fewer progenitors labeled at the early time point but equal number labeled at the intermediate time point, suggesting a recovery of neurogenesis. Notably, 56Fe particle exposure did not change the total number of nestin-expressing neural stem cells. These results highlight that despite the persistence of an index of genomic instability, 56Fe particle-induced deficits in adult hippocampal neurogenesis may be transient. These data support the regenerative capacity of the adult SGZ after HZE particle exposure and encourage additional inquiry into the relationship between radial glia stem cells and cognitive function after HZE particle exposure.
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Affiliation(s)
| | | | - Francisca Ahn
- Dept Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA
| | | | - Junie A. LeBlanc
- Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Shveta Malhotra
- Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Hung-Ying Shih
- Dept Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA
| | - David Petrik
- Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Neal Melvin
- Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Benjamin P.C. Chen
- Dept Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA
- Co-Corresponding Authors: Amelia J. Eisch, Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX 75390-9070. . Benjamin P. C. Chen, Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75390-9187.
| | - Amelia J. Eisch
- Dept Psychiatry, UT Southwestern Medical Center, Dallas, TX, USA
- Co-Corresponding Authors: Amelia J. Eisch, Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX 75390-9070. . Benjamin P. C. Chen, Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75390-9187.
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134
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O'Reilly KC, Kao HY, Lee H, Fenton AA. Converging on a core cognitive deficit: the impact of various neurodevelopmental insults on cognitive control. Front Neurosci 2014; 8:153. [PMID: 24966811 PMCID: PMC4052340 DOI: 10.3389/fnins.2014.00153] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 05/24/2014] [Indexed: 01/18/2023] Open
Abstract
Despite substantial effort and immense need, the treatment options for major neuropsychiatric illnesses like schizophrenia are limited and largely ineffective at improving the most debilitating cognitive symptoms that are central to mental illness. These symptoms include cognitive control deficits, the inability to selectively use information that is currently relevant and ignore what is currently irrelevant. Contemporary attempts to accelerate progress are in part founded on an effort to reconceptualize neuropsychiatric illness as a disorder of neural development. This neuro-developmental framework emphasizes abnormal neural circuits on the one hand, and on the other, it suggests there are therapeutic opportunities to exploit the developmental processes of excitatory neuron pruning, inhibitory neuron proliferation, elaboration of myelination, and other circuit refinements that extend through adolescence and into early adulthood. We have crafted a preclinical research program aimed at cognition failures that may be relevant to mental illness. By working with a variety of neurodevelopmental rodent models, we strive to identify a common pathophysiology that underlies cognitive control failure as well as a common strategy for improving cognition in the face of neural circuit abnormalities. Here we review our work to characterize cognitive control deficits in rats with a neonatal ventral hippocampus lesion and rats that were exposed to Methylazoxymethanol acetate (MAM) in utero. We review our findings as they pertain to early developmental processes, including neurogenesis, as well as the power of cognitive experience to refine neural circuit function within the mature and maturing brain's cognitive circuitry.
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Affiliation(s)
- Kally C O'Reilly
- Graduate Program in Neural and Behavioral Science, Downstate Medical Center, State University of New York Brooklyn, NY, USA
| | - Hsin-Yi Kao
- Graduate Program in Neural and Behavioral Science, Downstate Medical Center, State University of New York Brooklyn, NY, USA
| | - Heekyung Lee
- Graduate Program in Neural and Behavioral Science, Downstate Medical Center, State University of New York Brooklyn, NY, USA
| | - André A Fenton
- Neurobiology of Cognition Laboratory, Center for Neural Science, New York University New York, NY, USA ; The Robert F. Furchgott Center in Neural and Behavioral Science, Downstate Medical Center, State University of New York Brooklyn, NY, USA
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135
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Tannenholz L, Jimenez JC, Kheirbek MA. Local and regional heterogeneity underlying hippocampal modulation of cognition and mood. Front Behav Neurosci 2014; 8:147. [PMID: 24834033 PMCID: PMC4018538 DOI: 10.3389/fnbeh.2014.00147] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/11/2014] [Indexed: 11/17/2022] Open
Abstract
While the hippocampus has been classically studied for its role in learning and memory, there is significant support for a role of the HPC in regulating emotional behavior. Emerging research suggests these functions may be segregated along the dorsoventral axis of the HPC. In addition to this regional heterogeneity, within the HPC, the dentate gyrus is one of two areas in the adult brain where stem cells continuously give rise to new neurons. This process can influence and be modulated by the emotional state of the animal, suggesting that adult neurogenesis within the DG may contribute to psychiatric disorders and cognitive abilities. Yet, the exact mechanism by which these newborn neurons influence behavior remains unknown. Here, we will examine the contribution of hippocampal neurogenesis to the output of the HPC, and suggest that the role of neurogenesis may vary along the DV axis. Next, we will review literature indicating that anatomical connectivity varies along the DV axis of the HPC, and that this underlies the functional segregation along this axis. This analysis will allow us to synthesize novel hypotheses for the differential contribution of the HPC to cognition and mood.
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Affiliation(s)
- Lindsay Tannenholz
- Department of Pharmacology, Columbia University New York, NY, USA ; Division of Integrative Neuroscience, New York State Psychiatric Institute New York, NY, USA
| | - Jessica C Jimenez
- Division of Integrative Neuroscience, New York State Psychiatric Institute New York, NY, USA ; Department of Neuroscience, Columbia University New York, NY, USA
| | - Mazen A Kheirbek
- Division of Integrative Neuroscience, New York State Psychiatric Institute New York, NY, USA ; Department of Psychiatry, Columbia University New York, NY, USA
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136
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Hypothalamic subependymal niche: a novel site of the adult neurogenesis. Cell Mol Neurobiol 2014; 34:631-42. [PMID: 24744125 PMCID: PMC4047487 DOI: 10.1007/s10571-014-0058-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 04/02/2014] [Indexed: 12/15/2022]
Abstract
The discovery of undifferentiated, actively proliferating neural stem cells (NSCs) in the mature brain opened a brand new chapter in the contemporary neuroscience. Adult neurogenesis appears to occur in specific brain regions (including hypothalamus) throughout vertebrates’ life, being considered an important player in the processes of memory, learning, and neural plasticity. In the adult mammalian brain, NSCs are located mainly in the subgranular zone (SGZ) of the hippocampal dentate gyrus and in the subventricular zone (SVZ) of the lateral ventricle ependymal wall. Besides these classical regions, hypothalamic neurogenesis occurring mainly along and beneath the third ventricle wall seems to be especially well documented. Neurogenic zones in SGZ, SVZ, and in the hypothalamus share some particular common features like similar cellular cytoarchitecture, vascularization pattern, and extracellular matrix properties. Hypothalamic neurogenic niche is formed mainly by four special types of radial glia-like tanycytes. They are characterized by distinct expression of some neural progenitor and stem cell markers. Moreover, there are numerous suggestions that newborn hypothalamic neurons have a significant ability to integrate into the local neural pathways and to play important physiological roles, especially in the energy balance regulation. Newly formed neurons in the hypothalamus can synthesize and release food intake regulating neuropeptides and they are sensitive to the leptin. On the other hand, high-fat diet positively influences hypothalamic neurogenesis in rodents. The nature of this intriguing new site of adult neurogenesis is still so far poorly studied and requires further investigations.
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137
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Stuchlik A. Dynamic learning and memory, synaptic plasticity and neurogenesis: an update. Front Behav Neurosci 2014; 8:106. [PMID: 24744707 PMCID: PMC3978286 DOI: 10.3389/fnbeh.2014.00106] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 03/13/2014] [Indexed: 01/17/2023] Open
Abstract
Mammalian memory is the result of the interaction of millions of neurons in the brain and their coordinated activity. Candidate mechanisms for memory are synaptic plasticity changes, such as long-term potentiation (LTP). LTP is essentially an electrophysiological phenomenon manifested in hours-lasting increase on postsynaptic potentials after synapse tetanization. It is thought to ensure long-term changes in synaptic efficacy in distributed networks, leading to persistent changes in the behavioral patterns, actions and choices, which are often interpreted as the retention of information, i.e., memory. Interestingly, new neurons are born in the mammalian brain and adult hippocampal neurogenesis is proposed to provide a substrate for dynamic and flexible aspects of behavior such as pattern separation, prevention of interference, flexibility of behavior and memory resolution. This work provides a brief review on the memory and involvement of LTP and adult neurogenesis in memory phenomena.
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Affiliation(s)
- Ales Stuchlik
- Institute of Physiology, Academy of Sciences of the Czech Republic Prague, Czech Republic
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