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Ventura S, Duncan S, Ainge JA. Increased flexibility of CA3 memory representations following environmental enrichment. Curr Biol 2024; 34:2011-2019.e7. [PMID: 38636511 DOI: 10.1016/j.cub.2024.03.054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 02/16/2024] [Accepted: 03/25/2024] [Indexed: 04/20/2024]
Abstract
Environmental enrichment (EE) improves memory, particularly the ability to discriminate similar past experiences.1,2,3,4,5,6 The hippocampus supports this ability via pattern separation, the encoding of similar events using dissimilar memory representations.7 This is carried out in the dentate gyrus (DG) and CA3 subfields.8,9,10,11,12 Upregulation of adult neurogenesis in the DG improves memory through enhanced pattern separation.1,2,3,4,5,6,11,13,14,15,16 Adult-born granule cells (abGCs) in DG are suggested to contribute to pattern separation by driving inhibition in regions such as CA3,13,14,15,16,17,18 leading to sparser, nonoverlapping representations of similar events (although a role for abGCs in driving excitation in the hippocampus has also been reported16). Place cells in the hippocampus contribute to pattern separation by remapping to spatial and contextual alterations to the environment.19,20,21,22,23,24,25,26,27 How spatial responses in CA3 are affected by EE and input from increased numbers of abGCs in DG is, however, unknown. Here, we investigate the neural mechanisms facilitating improved memory following EE using associative recognition memory tasks that model the automatic and integrative nature of episodic memory. We find that EE-dependent improvements in difficult discriminations are related to increased neurogenesis and sparser memory representations across the hippocampus. Additionally, we report for the first time that EE changes how CA3 place cells discriminate similar contexts. CA3 place cells of enriched rats show greater spatial tuning, increased firing rates, and enhanced remapping to contextual changes. These findings point to more precise and flexible CA3 memory representations in enriched rats, which provides a putative mechanism for EE-dependent improvements in fine memory discrimination.
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Affiliation(s)
- Silvia Ventura
- School of Psychology & Neuroscience, University of St. Andrews, St. Mary's Quad, South Street, St. Andrews, Fife, Scotland KY16 9JP, UK
| | - Stephen Duncan
- School of Psychology & Neuroscience, University of St. Andrews, St. Mary's Quad, South Street, St. Andrews, Fife, Scotland KY16 9JP, UK; School of Psychological & Brain Sciences, Indiana University, 1101 E 10th Street, Bloomington, IN 47405, USA
| | - James A Ainge
- School of Psychology & Neuroscience, University of St. Andrews, St. Mary's Quad, South Street, St. Andrews, Fife, Scotland KY16 9JP, UK.
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2
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Jeong M, Jang JH, Oh SJ, Park J, Lee J, Hwang S, Oh YS. Maladaptation of dentate gyrus mossy cells mediates contextual discrimination deficit after traumatic stress. Cell Rep 2024; 43:114000. [PMID: 38527063 DOI: 10.1016/j.celrep.2024.114000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 02/15/2024] [Accepted: 03/10/2024] [Indexed: 03/27/2024] Open
Abstract
Fear overgeneralization is a maladaptive response to traumatic stress that is associated with the inability to discriminate between threat and safety contexts, a hallmark feature of post-traumatic stress disorder (PTSD). However, the neural mechanisms underlying this deficit remain unclear. Here, we show that traumatic stress exposure impairs contextual discrimination between threat and safety contexts in the learned helplessness (LH) model. Mossy cells (MCs) in the dorsal hippocampus are suppressed in response to traumatic stress. Bidirectional manipulation of MC activity in the LH model reveals that MC inhibition is causally linked to impaired contextual discrimination. Mechanistically, MC inhibition increases the number of active granule cells in a given context, significantly overlapping context-specific ensembles. Our study demonstrates that maladaptive inhibition of MCs after traumatic stress is a substantial mechanism underlying fear overgeneralization with contextual discrimination deficit, suggesting a potential therapeutic target for cognitive symptoms of PTSD.
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Affiliation(s)
- Minseok Jeong
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea
| | - Jin-Hyeok Jang
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea
| | - Seo-Jin Oh
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea
| | - Jeongrak Park
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea
| | - Junseop Lee
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea
| | - Sehyeon Hwang
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea
| | - Yong-Seok Oh
- Department of Brain Sciences, Daegu-Gyeongbuk Institute of Science and Technology, Hyeonpung-eup, Dalseong-gun, Daegu 42988, Republic of Korea; Emotion, Cognition & Behavior Research Group, Korea Brain Research Institute, 61 Cheomdan-ro, Daegu 41062, Republic of Korea.
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3
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Li H, Tamura R, Hayashi D, Asai H, Koga J, Ando S, Yokota S, Kaneko J, Sakurai K, Sumiyoshi A, Yamamoto T, Hikishima K, Tanaka KZ, McHugh TJ, Hisatsune T. Silencing dentate newborn neurons alters excitatory/inhibitory balance and impairs behavioral inhibition and flexibility. SCIENCE ADVANCES 2024; 10:eadk4741. [PMID: 38198539 PMCID: PMC10780870 DOI: 10.1126/sciadv.adk4741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 12/13/2023] [Indexed: 01/12/2024]
Abstract
Adult neurogenesis confers the hippocampus with unparalleled neural plasticity, essential for intricate cognitive functions. The specific influence of sparse newborn neurons (NBNs) in modulating neural activities and subsequently steering behavior, however, remains obscure. Using an engineered NBN-tetanus toxin mouse model (NBN-TeTX), we noninvasively silenced NBNs, elucidating their crucial role in impulse inhibition and cognitive flexibility as evidenced through Morris water maze reversal learning and Go/Nogo task in operant learning. Task-based functional MRI (tb-fMRI) paired with operant learning revealed dorsal hippocampal hyperactivation during the Nogo task in male NBN-TeTX mice, suggesting that hippocampal hyperexcitability might underlie the observed behavioral deficits. Additionally, resting-state fMRI (rs-fMRI) exhibited enhanced functional connectivity between the dorsal and ventral dentate gyrus following NBN silencing. Further investigations into the activities of PV+ interneurons and mossy cells highlighted the indispensability of NBNs in maintaining the hippocampal excitation/inhibition balance. Our findings emphasize that the neural plasticity driven by NBNs extensively modulates the hippocampus, sculpting inhibitory control and cognitive flexibility.
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Affiliation(s)
- Haowei Li
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Risako Tamura
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Daiki Hayashi
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Hirotaka Asai
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Junya Koga
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Shota Ando
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Sayumi Yokota
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Jun Kaneko
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Keisuke Sakurai
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Akira Sumiyoshi
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Tadashi Yamamoto
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Keigo Hikishima
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Kazumasa Z. Tanaka
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
| | - Thomas J. McHugh
- Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
| | - Tatsuhiro Hisatsune
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
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4
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Berdugo‐Vega G, Dhingra S, Calegari F. Sharpening the blades of the dentate gyrus: how adult-born neurons differentially modulate diverse aspects of hippocampal learning and memory. EMBO J 2023; 42:e113524. [PMID: 37743770 PMCID: PMC11059975 DOI: 10.15252/embj.2023113524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 06/19/2023] [Accepted: 08/18/2023] [Indexed: 09/26/2023] Open
Abstract
For decades, the mammalian hippocampus has been the focus of cellular, anatomical, behavioral, and computational studies aimed at understanding the fundamental mechanisms underlying cognition. Long recognized as the brain's seat for learning and memory, a wealth of knowledge has been accumulated on how the hippocampus processes sensory input, builds complex associations between objects, events, and space, and stores this information in the form of memories to be retrieved later in life. However, despite major efforts, our understanding of hippocampal cognitive function remains fragmentary, and models trying to explain it are continually revisited. Here, we review the literature across all above-mentioned domains and offer a new perspective by bringing attention to the most distinctive, and generally neglected, feature of the mammalian hippocampal formation, namely, the structural separability of the two blades of the dentate gyrus into "supra-pyramidal" and "infra-pyramidal". Next, we discuss recent reports supporting differential effects of adult neurogenesis in the regulation of mature granule cell activity in these two blades. We propose a model for how differences in connectivity and adult neurogenesis in the two blades can potentially provide a substrate for subtly different cognitive functions.
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Affiliation(s)
- Gabriel Berdugo‐Vega
- CRTD‐Center for Regenerative Therapies DresdenTechnische Universität DresdenDresdenGermany
- Present address:
Laboratory of Neuroepigenetics, Brain Mind Institute, School of Life Sciences, École Polytechnique Fédérale Lausanne (EPFL)LausanneSwitzerland
| | - Shonali Dhingra
- CRTD‐Center for Regenerative Therapies DresdenTechnische Universität DresdenDresdenGermany
| | - Federico Calegari
- CRTD‐Center for Regenerative Therapies DresdenTechnische Universität DresdenDresdenGermany
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5
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Mañas-Padilla MC, Melgar-Locatelli S, Vicente L, Gil-Rodríguez S, Rivera P, Rodríguez-Pérez C, Castilla-Ortega E. Temozolomide treatment inhibits spontaneous motivation for exploring a complex object in mice: A potential role of adult hippocampal neurogenesis in "curiosity". J Comp Neurol 2023; 531:548-560. [PMID: 36515664 PMCID: PMC10107499 DOI: 10.1002/cne.25442] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 11/02/2022] [Accepted: 11/26/2022] [Indexed: 12/15/2022]
Abstract
Intrinsic exploratory biases are an innate motivation for exploring certain types of stimuli or environments over others, and they may be associated with cognitive, emotional, and even personality-like traits. However, their neurobiological basis has been scarcely investigated. Considering the involvement of the hippocampus in novelty recognition and in spatial and pattern separation tasks, this work researched the role of adult hippocampal neurogenesis (AHN) in intrinsic exploratory bias for a perceptually complex object in mice. Spontaneous object preference tasks revealed that both male and female C57BL/6J mice showed a consistent unconditioned preference for exploring "complex"-irregular-objects over simpler ones. Furthermore, increasing objects' complexity resulted in an augmented time of object exploration. In a different experiment, male mice received either vehicle or the DNA alkylating agent temozolomide (TMZ) for 4 weeks, a pharmacological treatment that reduced AHN as evidenced by immunohistochemistry. After assessment in a behavioral test battery, the TMZ-treated mice did not show any alterations in general exploratory and anxiety-like responses. However, when tested in the spontaneous object preference task, the TMZ-treated mice did not display enhanced exploration of the complex object, as evidenced both by a reduced exploration time-specifically for the complex object-and a lack of preference for the complex object over the simple one. This study supports a novel role of AHN in intrinsic exploratory bias for perceptual complexity. Moreover, the spontaneous complex object preference task as a rodent model of "curiosity" is discussed.
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Affiliation(s)
- M Carmen Mañas-Padilla
- Instituto de Investigación Biomédica de Málaga-IBIMA, Málaga, Spain.,Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Universidad de Málaga, Málaga, Spain
| | - Sonia Melgar-Locatelli
- Instituto de Investigación Biomédica de Málaga-IBIMA, Málaga, Spain.,Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Universidad de Málaga, Málaga, Spain
| | - Lucía Vicente
- Centro de Experimentación y Conducta Animal, Universidad de Málaga, Málaga, Spain.,Departamento de Psicología, Universidad de Deusto, Bilbao, Spain
| | - Sara Gil-Rodríguez
- Instituto de Investigación Biomédica de Málaga-IBIMA, Málaga, Spain.,Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Universidad de Málaga, Málaga, Spain
| | - Patricia Rivera
- Instituto de Investigación Biomédica de Málaga-IBIMA, Málaga, Spain.,Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, Málaga, Spain
| | - Celia Rodríguez-Pérez
- Departamento de Nutrición y Bromatología, Universidad de Granada, Campus de Melilla, Melilla, Spain.,Instituto de Nutrición y Tecnología de los Alimentos 'José Mataix', Universidad de Granada, Granada, Spain.,Instituto de Investigación Biosanitaria de Granada (ibs.GRANADA), Granada, Spain
| | - Estela Castilla-Ortega
- Instituto de Investigación Biomédica de Málaga-IBIMA, Málaga, Spain.,Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Universidad de Málaga, Málaga, Spain
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6
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Ash AM, Regele-Blasco E, Seib DR, Chahley E, Skelton PD, Luikart BW, Snyder JS. Adult-born neurons inhibit developmentally-born neurons during spatial learning. Neurobiol Learn Mem 2023; 198:107710. [PMID: 36572174 DOI: 10.1016/j.nlm.2022.107710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 12/20/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
Ongoing neurogenesis in the dentate gyrus (DG) subregion of the hippocampus results in a heterogenous population of neurons. Immature adult-born neurons (ABNs) have physiological and anatomical properties that may give them a unique role in learning. For example, compared to older granule neurons, they have greater somatic excitability, which could facilitate their recruitment into memory traces. However, recruitment is also likely to depend on interactions with other DG neurons through processes such as lateral inhibition. Immature ABNs target inhibitory interneurons and, compared to older neurons, they receive less GABAergic inhibition. Thus, they may induce lateral inhibition of mature DG neurons while being less susceptible to inhibition themselves. To test this we used a chemogenetic approach to silence immature ABNs as rats learned a spatial water maze task, and measured activity (Fos expression) in ABNs and developmentally-born neurons (DBNs). A retrovirus expressing the inhibitory DREADD receptor, hM4Di, was injected into the dorsal DG of male rats at 6w to infect neurons born in adulthood. Animals were also injected with BrdU to label DBNs or ABNs. DBNs were significantly more active than immature 4-week-old ABNs. Silencing 4-week-old ABNs did not alter learning but it increased activity in DBNs. However, silencing ABNs did not affect activation in other ABNs within the DG. Silencing ABNs also did not alter Fos expression in parvalbumin- and somatostatin-expressing interneurons. Collectively, these results suggest that ABNs may directly inhibit DBN activity during hippocampal-dependent learning, which may be relevant for maintaining sparse hippocampal representations of experienced events.
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Affiliation(s)
- Alyssa M Ash
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Elena Regele-Blasco
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Désirée R Seib
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Erin Chahley
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Patrick D Skelton
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, United States
| | - Bryan W Luikart
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, United States
| | - Jason S Snyder
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
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7
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Oberländer K, Witte V, Mallien AS, Gass P, Bengtson CP, Bading H. Dysregulation of Npas4 and Inhba expression and an altered excitation-inhibition balance are associated with cognitive deficits in DBA/2 mice. Learn Mem 2022; 29:55-70. [PMID: 35042829 PMCID: PMC8774195 DOI: 10.1101/lm.053527.121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 11/28/2021] [Indexed: 02/03/2023]
Abstract
Differences in the learning associated transcriptional profiles between mouse strains with distinct learning abilities could provide insight into the molecular basis of learning and memory. The inbred mouse strain DBA/2 shows deficits in hippocampus-dependent memory, yet the transcriptional responses to learning and the underlying mechanisms of the impairments are unknown. Comparing DBA/2J mice with the reference standard C57BL/6N mouse strain we verify an enhanced susceptibility to kainic acid induced seizures, confirm impairments in hippocampus-dependent spatial memory tasks and uncover additional behavioral abnormalities including deficits in hippocampus-independent learning. Surprisingly, we found no broad dysfunction of the DBA/2J strain in immediate early gene (IEG) activation but instead report brain region-specific and gene-specific alterations. The learning-associated IEGs Arc, c-Fos, and Nr4a1 showed no DBA/2J deficits in basal or synaptic activity induced gene expression in hippocampal or cortical primary neuronal cultures or in the CA1, CA3, or retrosplenial cortex following spatial object recognition (SOR) training in vivo. However, the parietal cortex showed reduced and the dentate gyrus showed enhanced SOR-evoked induction of most IEGs. All DBA/2J hippocampal regions exhibited elevated basal expression of inhibin β A (Inhba) and a learning-associated superinduction of the transcription factor neuronal Per-Arnt-Sim domain protein 4 (Npas4) known to regulate the synaptic excitation-inhibition balance. In line with this, CA1 pyramidal neurons of DBA/2J mice showed fewer inhibitory and more excitatory miniature postsynaptic currents but no alteration in most other electrophysiological properties or gross dendritic morphology. The dysregulation of Npas4 and Inhba expression and synaptic connectivity may underlie the cognitive deficits and increased susceptibility to seizures of DBA/2J mice.
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Affiliation(s)
- Kristin Oberländer
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, 69120 Heidelberg, Germany
| | - Victoria Witte
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, 69120 Heidelberg, Germany
| | - Anne Stephanie Mallien
- Department of Psychiatry and Psychotherapy, Research Group Animal Models in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, 68159 Mannheim, Germany
| | - Peter Gass
- Department of Psychiatry and Psychotherapy, Research Group Animal Models in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, 68159 Mannheim, Germany
| | - C. Peter Bengtson
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, 69120 Heidelberg, Germany
| | - Hilmar Bading
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, 69120 Heidelberg, Germany
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8
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Hernández-Mercado K, Zepeda A. Morris Water Maze and Contextual Fear Conditioning Tasks to Evaluate Cognitive Functions Associated With Adult Hippocampal Neurogenesis. Front Neurosci 2022; 15:782947. [PMID: 35046769 PMCID: PMC8761726 DOI: 10.3389/fnins.2021.782947] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022] Open
Abstract
New neurons are continuously generated and functionally integrated into the dentate gyrus (DG) network during the adult lifespan of most mammals. The hippocampus is a crucial structure for spatial learning and memory, and the addition of new neurons into the DG circuitry of rodents seems to be a key element for these processes to occur. The Morris water maze (MWM) and contextual fear conditioning (CFC) are among the most commonly used hippocampus-dependent behavioral tasks to study episodic-like learning and memory in rodents. While the functional contribution of adult hippocampal neurogenesis (AHN) through these paradigms has been widely addressed, results have generated controversial findings. In this review, we analyze and discuss possible factors in the experimental methods that could explain the inconsistent results among AHN studies; moreover, we provide specific suggestions for the design of more sensitive protocols to assess AHN-mediated learning and memory functions.
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Affiliation(s)
- Karina Hernández-Mercado
- Departamento de Medicina Genómica y Toxicológia Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Angélica Zepeda
- Departamento de Medicina Genómica y Toxicológia Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
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9
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Domínguez-Rivas E, Ávila-Muñoz E, Schwarzacher SW, Zepeda A. Adult hippocampal neurogenesis in the context of lipopolysaccharide-induced neuroinflammation: A molecular, cellular and behavioral review. Brain Behav Immun 2021; 97:286-302. [PMID: 34174334 DOI: 10.1016/j.bbi.2021.06.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 06/17/2021] [Accepted: 06/19/2021] [Indexed: 12/17/2022] Open
Abstract
The continuous generation of new neurons occurs in at least two well-defined niches in the adult rodent brain. One of these areas is the subgranular zone of the dentate gyrus (DG) in the hippocampus. While the DG is associated with contextual and spatial learning and memory, hippocampal neurogenesis is necessary for pattern separation. Hippocampal neurogenesis begins with the activation of neural stem cells and culminates with the maturation and functional integration of a portion of the newly generated glutamatergic neurons into the hippocampal circuits. The neurogenic process is continuously modulated by intrinsic factors, one of which is neuroinflammation. The administration of lipopolysaccharide (LPS) has been widely used as a model of neuroinflammation and has yielded a body of evidence for unveiling the detrimental impact of inflammation upon the neurogenic process. This work aims to provide a comprehensive overview of the current knowledge on the effects of the systemic and central administration of LPS upon the different stages of neurogenesis and discuss their effects at the molecular, cellular, and behavioral levels.
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Affiliation(s)
- Eduardo Domínguez-Rivas
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Evangelina Ávila-Muñoz
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Stephan W Schwarzacher
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Angélica Zepeda
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico; Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt am Main, Germany.
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10
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Ogando MB, Pedroncini O, Federman N, Romano SA, Brum LA, Lanuza GM, Refojo D, Marin-Burgin A. Cholinergic modulation of dentate gyrus processing through dynamic reconfiguration of inhibitory circuits. Cell Rep 2021; 36:109572. [PMID: 34433032 DOI: 10.1016/j.celrep.2021.109572] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 06/28/2021] [Accepted: 07/30/2021] [Indexed: 10/20/2022] Open
Abstract
The dentate gyrus (DG) of the hippocampus plays a key role in memory formation, and it is known to be modulated by septal projections. By performing electrophysiology and optogenetics, we evaluated the role of cholinergic modulation in the processing of afferent inputs in the DG. We show that mature granule cells (GCs), but not adult-born immature neurons, have increased responses to afferent perforant path stimuli upon cholinergic modulation. This is due to a highly precise reconfiguration of inhibitory circuits, differentially affecting Parvalbumin and Somatostatin interneurons, resulting in a nicotinic-dependent perisomatic disinhibition of GCs. This circuit reorganization provides a mechanism by which mature GCs could escape the strong inhibition they receive, creating a window of opportunity for plasticity. Indeed, coincident activation of perforant path inputs with optogenetic release of acetylcholine produces a long-term potentiated response in GCs, essential for memory formation.
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Affiliation(s)
- Mora B Ogando
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society Godoy Cruz 2390, C1425FQD Buenos Aires, Argentina.
| | - Olivia Pedroncini
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society Godoy Cruz 2390, C1425FQD Buenos Aires, Argentina
| | - Noel Federman
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society Godoy Cruz 2390, C1425FQD Buenos Aires, Argentina
| | - Sebastián A Romano
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society Godoy Cruz 2390, C1425FQD Buenos Aires, Argentina
| | - Luciano A Brum
- Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Patricias Argentinas 435, Buenos Aires C1405BWE, Argentina
| | - Guillermo M Lanuza
- Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Patricias Argentinas 435, Buenos Aires C1405BWE, Argentina
| | - Damian Refojo
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society Godoy Cruz 2390, C1425FQD Buenos Aires, Argentina
| | - Antonia Marin-Burgin
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society Godoy Cruz 2390, C1425FQD Buenos Aires, Argentina.
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11
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Leschik J, Lutz B, Gentile A. Stress-Related Dysfunction of Adult Hippocampal Neurogenesis-An Attempt for Understanding Resilience? Int J Mol Sci 2021; 22:7339. [PMID: 34298958 PMCID: PMC8305135 DOI: 10.3390/ijms22147339] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/02/2021] [Accepted: 07/05/2021] [Indexed: 12/16/2022] Open
Abstract
Newborn neurons in the adult hippocampus are regulated by many intrinsic and extrinsic cues. It is well accepted that elevated glucocorticoid levels lead to downregulation of adult neurogenesis, which this review discusses as one reason why psychiatric diseases, such as major depression, develop after long-term stress exposure. In reverse, adult neurogenesis has been suggested to protect against stress-induced major depression, and hence, could serve as a resilience mechanism. In this review, we will summarize current knowledge about the functional relation of adult neurogenesis and stress in health and disease. A special focus will lie on the mechanisms underlying the cascades of events from prolonged high glucocorticoid concentrations to reduced numbers of newborn neurons. In addition to neurotransmitter and neurotrophic factor dysregulation, these mechanisms include immunomodulatory pathways, as well as microbiota changes influencing the gut-brain axis. Finally, we discuss recent findings delineating the role of adult neurogenesis in stress resilience.
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Affiliation(s)
- Julia Leschik
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, 55128 Mainz, Germany;
| | - Beat Lutz
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, 55128 Mainz, Germany;
- Leibniz Institute for Resilience Research (LIR), 55122 Mainz, Germany
| | - Antonietta Gentile
- Synaptic Immunopathology Lab, IRCCS San Raffaele Pisana, 00166 Rome, Italy;
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12
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Berdugo-Vega G, Lee CC, Garthe A, Kempermann G, Calegari F. Adult-born neurons promote cognitive flexibility by improving memory precision and indexing. Hippocampus 2021; 31:1068-1079. [PMID: 34174010 DOI: 10.1002/hipo.23373] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/26/2021] [Accepted: 06/06/2021] [Indexed: 11/12/2022]
Abstract
Adult neurogenesis in the hippocampal dentate gyrus (DG) is an extraordinary form of plasticity fundamental for cognitive flexibility. Recent evidence showed that newborn neurons differentially modulate input to the infra- and supra-pyramidal blades of the DG during the processing of spatial and contextual information, respectively. However, how this differential regulation by neurogenesis is translated into different aspects contributing cognitive flexibility is unclear. Here, we increased adult-born neurons by a genetic expansion of neural stem cells and studied their influence during navigational learning. We found that increased neurogenesis improved both memory precision and flexibility. Interestingly, each of these gains was associated with distinct subregional patterns of activity and better separation of memory representations in the DG-CA3 network. Our results highlight the role of adult-born neurons in promoting memory precision and indexing and suggests their anatomical allocation within specific DG-CA3 compartments, together contributing to cognitive flexibility.
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Affiliation(s)
- Gabriel Berdugo-Vega
- CRTD-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Chi-Chieh Lee
- CRTD-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Alexander Garthe
- CRTD-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany.,DZNE-German Center for Neurodegenerative Diseases, Dresden, Germany
| | - Gerd Kempermann
- CRTD-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany.,DZNE-German Center for Neurodegenerative Diseases, Dresden, Germany
| | - Federico Calegari
- CRTD-Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
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13
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Effects of classical PKC activation on hippocampal neurogenesis and cognitive performance: mechanism of action. Neuropsychopharmacology 2021; 46:1207-1219. [PMID: 33335309 PMCID: PMC8115324 DOI: 10.1038/s41386-020-00934-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 11/24/2020] [Accepted: 11/30/2020] [Indexed: 12/27/2022]
Abstract
Hippocampal neurogenesis has widely been linked to memory and learning performance. New neurons generated from neural stem cells (NSC) within the dentate gyrus of the hippocampus (DG) integrate in hippocampal circuitry participating in memory tasks. Several neurological and neuropsychiatric disorders show cognitive impairment together with a reduction in DG neurogenesis. Growth factors secreted within the DG promote neurogenesis. Protein kinases of the protein kinase C (PKC) family facilitate the release of several of these growth factors, highlighting the role of PKC isozymes as key target molecules for the development of drugs that induce hippocampal neurogenesis. PKC activating diterpenes have been shown to facilitate NSC proliferation in neurogenic niches when injected intracerebroventricularly. We show in here that long-term administration of diterpene ER272 promotes neurogenesis in the subventricular zone and in the DG of mice, affecting neuroblasts differentiation and neuronal maturation. A concomitant improvement in learning and spatial memory tasks performance can be observed. Insights into the mechanism of action reveal that this compound facilitates classical PKCα activation and promotes transforming growth factor alpha (TGFα) and, to a lesser extent, neuregulin release. Our results highlight the role of this molecule in the development of pharmacological drugs to treat neurological and neuropsychiatric disorders associated with memory loss and a deficient neurogenesis.
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14
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Groisman AI, Yang SM, Schinder AF. Differential Coupling of Adult-Born Granule Cells to Parvalbumin and Somatostatin Interneurons. Cell Rep 2021; 30:202-214.e4. [PMID: 31914387 PMCID: PMC7011182 DOI: 10.1016/j.celrep.2019.12.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 10/16/2019] [Accepted: 11/27/2019] [Indexed: 12/29/2022] Open
Abstract
A strong GABAergic tone imposes sparse levels of activity in the dentate gyrus of the hippocampus. This balance is challenged by the addition of new granule cells (GCs) with high excitability. How developing GCs integrate within local inhibitory networks remains unknown. We used optogenetics to study synaptogenesis between new GCs and GABAergic interneurons expressing parvalbumin (PV-INs) and somatostatin (SST-INs). PV-INs target the soma, and synapses become mature after 6 weeks. This transition is accelerated by exposure to an enriched environment. PV-INs exert efficient control of GC spiking and participate in both feedforward and feedback loops, a mechanism that would favor lateral inhibition and sparse coding. SST-INs target the dendrites, and synapses mature after 8 weeks. Outputs from GCs onto PV-INs develop faster than those onto SST-INs. Our results reveal a long-lasting transition wherein adult-born neurons remain poorly coupled to inhibition, which might enhance activity-dependent plasticity of input and output synapses. Groisman et al. examine the integration of adult-born granule cells (GCs) to inhibitory networks of the adult hippocampus. Synapse maturation is remarkably slow for parvalbumin and somatostatin interneurons, both for connections toward and from GCs. Inhibition controls the activity of new GCs late in development.
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Affiliation(s)
- Ayelén I Groisman
- Laboratorio de Plasticidad Neuronal, Fundación Instituto Leloir, Av. Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Sung M Yang
- Laboratorio de Plasticidad Neuronal, Fundación Instituto Leloir, Av. Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Alejandro F Schinder
- Laboratorio de Plasticidad Neuronal, Fundación Instituto Leloir, Av. Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina.
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15
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Taha E, Patil S, Barrera I, Panov J, Khamaisy M, Proud CG, Bramham CR, Rosenblum K. eEF2/eEF2K Pathway in the Mature Dentate Gyrus Determines Neurogenesis Level and Cognition. Curr Biol 2020; 30:3507-3521.e7. [PMID: 32707059 DOI: 10.1016/j.cub.2020.06.061] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 05/08/2020] [Accepted: 06/18/2020] [Indexed: 12/13/2022]
Abstract
Levels of adult neurogenesis in the dentate gyrus (DG) of the hippocampus are correlated with unique cognitive functions. However, the molecular pathways controlling it are poorly understood. Here, we found that the known physiological ways to enhance neurogenesis converged on the eEF2/eEF2K pathway via AMPK in the DG. Enhancing the elongation phase of mRNA translation in eEF2K-knockout (eEF2K-KO) mice induced the expression of neurogenesis-related proteins in the hippocampus. We thus tested the hypothesis that inducing eEF2K-KO in mature neurons of the DG controls neurogenesis. Indeed, both general eEF2K-KO and targeted KO in DG excitatory mature neurons resulted in enhanced neurogenesis levels and upregulation of neurogenesis-related proteins. Increased neurogenesis was correlated with enhanced performance in DG-dependent learning. Moreover, general and local eEF2K-KO in old mice rejuvenated the DG, paving the way for better mechanistic understanding of how neurogenesis is controlled in the mature DG and possible treatments for incurable aging-associated diseases.
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Affiliation(s)
- Elham Taha
- Sagol Department of Neurobiology, 199 Aba Khoushy Avenue Mount Carmel, University of Haifa, 3498838 Haifa, Israel
| | - Sudarshan Patil
- Department of Biomedicine and KG Jebsen Centre for Research on Neuropsychiatric Disorders, Jonas Lies vei 91, University of Bergen, 5009 Bergen, Norway
| | - Iliana Barrera
- Sagol Department of Neurobiology, 199 Aba Khoushy Avenue Mount Carmel, University of Haifa, 3498838 Haifa, Israel
| | - Julia Panov
- Sagol Department of Neurobiology, 199 Aba Khoushy Avenue Mount Carmel, University of Haifa, 3498838 Haifa, Israel
| | - Mohammad Khamaisy
- Sagol Department of Neurobiology, 199 Aba Khoushy Avenue Mount Carmel, University of Haifa, 3498838 Haifa, Israel
| | - Christopher G Proud
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia; Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute, PO Box 11060, 5001 Adelaide, SA, Australia
| | - Clive R Bramham
- Department of Biomedicine and KG Jebsen Centre for Research on Neuropsychiatric Disorders, Jonas Lies vei 91, University of Bergen, 5009 Bergen, Norway
| | - Kobi Rosenblum
- Sagol Department of Neurobiology, 199 Aba Khoushy Avenue Mount Carmel, University of Haifa, 3498838 Haifa, Israel; Center for Gene Manipulation in the Brain, 199 Aba Khoushy Avenue Mount Carmel, University of Haifa, 3498838 Haifa, Israel.
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16
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Increasing neurogenesis refines hippocampal activity rejuvenating navigational learning strategies and contextual memory throughout life. Nat Commun 2020; 11:135. [PMID: 31919362 PMCID: PMC6952376 DOI: 10.1038/s41467-019-14026-z] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 12/12/2019] [Indexed: 01/24/2023] Open
Abstract
Functional plasticity of the brain decreases during ageing causing marked deficits in contextual learning, allocentric navigation and episodic memory. Adult neurogenesis is a prime example of hippocampal plasticity promoting the contextualisation of information and dramatically decreases during ageing. We found that a genetically-driven expansion of neural stem cells by overexpression of the cell cycle regulators Cdk4/cyclinD1 compensated the age-related decline in neurogenesis. This triggered an overall inhibitory effect on the trisynaptic hippocampal circuit resulting in a changed profile of CA1 sharp-wave ripples known to underlie memory consolidation. Most importantly, increased neurogenesis rescued the age-related switch from hippocampal to striatal learning strategies by rescuing allocentric navigation and contextual memory. Our study demonstrates that critical aspects of hippocampal function can be reversed in old age, or compensated throughout life, by exploiting the brain’s endogenous reserve of neural stem cells. Ageing affects several brain areas causing a decrease in cognitive abilities and memory. We find that increasing the endogenous potential of the hippocampus to generate new neurons throughout life rejuvenates learning and memory, indicating that neural reserves can be exploited during ageing to compensate for age- or disease-related cognitive impairments.
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17
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Tran LM, Josselyn SA, Richards BA, Frankland PW. Forgetting at biologically realistic levels of neurogenesis in a large-scale hippocampal model. Behav Brain Res 2019; 376:112180. [PMID: 31472193 PMCID: PMC8719326 DOI: 10.1016/j.bbr.2019.112180] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/19/2019] [Accepted: 08/24/2019] [Indexed: 11/18/2022]
Abstract
Neurogenesis persists throughout life in the dentate gyrus region of the mammalian hippocampus. Computational models have established that the addition of neurons degrades existing memories (i.e., produces forgetting). These predictions are supported by empirical observations in rodents, where post-training increases in neurogenesis also promote forgetting of hippocampus-dependent memories. However, in these computational models which use 10-1,000 neurons to represent the dentate gyrus, forgetting is only observed at rates of new neuron addition that greatly exceed adult neurogenesis rates observed in vivo. In order to address this, here we generated an artificial neural network which incorporated more realistic features of the hippocampus - including increased network size (with up to 20,000 dentate gyrus neurons), sparse activity, and sparse connectivity - features that were not present in earlier models. In addition, we explored how properties of new neurons - their connectivity, excitability, and plasticity - impact forgetting using a pattern categorization task. Our results revealed that neurogenic networks forget previously learned input-output pattern associations. This forgetting predicted a performance enhancement in subsequent conflictual learning, compared to static networks (with no added neurons). These effects were especially sensitive to changes in increased output connectivity and excitability of new neurons. Crucially, forgetting was observed at much lower rates of neurogenesis in larger networks, with the addition of as little as 0.2% of the total DG population sufficient to induce forgetting.
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Affiliation(s)
- Lina M Tran
- Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, ON, Canada; Dept. of Physiology, University of Toronto, Toronto, ON, Canada; Vector Institute, Toronto, ON, Canada
| | - Sheena A Josselyn
- Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, ON, Canada; Dept. of Physiology, University of Toronto, Toronto, ON, Canada; Dept. of Psychology, University of Toronto, Toronto, ON, Canada; Institute of Medical Sciences, University of TorontoToronto, ON, Canada; Brain, Mind and Consciousness Program, Canadian Institute for Advanced Research, Toronto, ON, Canada
| | - Blake A Richards
- Mila, Montreal, QC, Canada; School of Computer Science, McGill University, Montreal, QC, Canada; Dept. of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; Canadian Institute for Advanced Research, Toronto, ON, Canada
| | - Paul W Frankland
- Neuroscience and Mental Health, The Hospital for Sick Children, Toronto, ON, Canada; Dept. of Physiology, University of Toronto, Toronto, ON, Canada; Dept. of Psychology, University of Toronto, Toronto, ON, Canada; Institute of Medical Sciences, University of TorontoToronto, ON, Canada; Child and Brain Development Program, Canadian Institute for Advanced Research, Toronto, ON, Canada.
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18
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Corrubia L, Santhakumar V. Born to Be Wild: A Case for Targeting Ectopic Adult Born Granule Cells for Seizure Control. Epilepsy Curr 2019; 20:57-60. [PMID: 32037879 PMCID: PMC7020538 DOI: 10.1177/1535759719891438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Altered Synaptic Drive Onto Birthdated Dentate Granule Cells in Experimental Temporal Lobe Epilepsy Althaus AL, Moore SJ, Zhang H, Du Plummer X, Murphy GG, Parent JM. J Neurosci. 2019;39(38):7604-7614. doi:10.1523/JNEUROSCI.0654-18.2019. Dysregulated adult hippocampal neurogenesis occurs in many temporal lobe epilepsy (TLE) models. Most dentate granule cells (DGCs) generated in response to an epileptic insult develop features that promote increased excitability, including ectopic location, persistent hilar basal dendrites (HBDs), and mossy fiber sprouting. However, some appear to integrate normally and even exhibit reduced excitability compared to other DGCs. To examine the relationship between DGC birthdate, morphology, and network integration in a model of TLE, we retrovirally birth-dated either early-born (postnatal day 7) or adult-born (postnatal day 60) DGCs. Male rats underwent pilocarpine-induced status epilepticus (SE) or sham treatment at postnatal day 56. Three to six months after SE or sham treatment, we used whole-cell patch clamp and fluorescence microscopy to record spontaneous excitatory and inhibitory currents from birth-dated DGCs. We found that both adult-born and early-born populations of DGCs recorded from epileptic rats received increased excitatory input compared with age-matched controls. Interestingly, when adult-born populations were separated into normally integrated (normotopic) and aberrant (ectopic or HBD containing) subpopulations, only the aberrant populations exhibited a relative increase in excitatory input (amplitude, frequency, and charge transfer). The ratio of excitatory to inhibitory input was most dramatically upregulated for ectopically localized DGCs. These data provide definitive physiological evidence that aberrant integration of post-SE, adult-born DGCs contributes to increased synaptic drive and supports the idea that ectopic DGCs serve as putative hub cells to promote seizures. Significance Statement: Adult DGC neurogenesis is altered in rodent models of TLE. Some of the new neurons show abnormal morphology and integration, but whether adult-generated DGCs contribute to the development of epilepsy is controversial. We examined the synaptic inputs of age-defined populations of DGCs using electrophysiological recordings and fluorescent retroviral reporter birth-dating. Dentate granule cells generated neonatally were compared with those generated in adulthood, and adult-born neurons with normal versus aberrant morphology or integration were examined. We found that adult-born, ectopically located DGCs exhibit the most pro-excitatory physiological changes, implicating this population in seizure generation or progression. Targeting Seizure-Induced Neurogenesis in a Clinically Relevant Time Period Leads to Transient But Not Persistent Seizure Reduction Varma P, Brulet R, Zhang L, Hsieh J. J Neurosci. 2019;39(35):7019-7028. doi:10.1523/JNEUROSCI.0920-19.2019. Mesial temporal lobe epilepsy (mTLE), the most common form of medically refractory epilepsy in adults, is usually associated with hippocampal pathophysiology. Using rodent models of mTLE, many studies including work from our laboratory have shown that new neurons born around the onset of severe acute seizures known as status epilepticus (SE) are crucial for the process of epileptogenesis and targeting seizure-induced neurogenesis either genetically or pharmacologically can impact the frequency of chronic seizures. However, these studies are limited in their clinical relevance as none of them determines the potential of blocking new neurons generated after the epileptogenic insult to alleviate the development of chronic seizures. Therefore, using a pilocarpine-induced SE model of mTLE in mice of either sex, we show that >4 weeks of continuous and concurrent ablation of seizure-induced neurogenesis after SE can reduce the formation of spontaneous recurrent seizures by 65%. We also found that blocking post-SE neurogenesis does not lead to long-term seizure reduction as the effect was observed only transiently for 10 days with >4 weeks of continuous and concurrent ablation of seizure-induced neurogenesis. Thus, these findings provide evidence that seizure-induced neurogenesis when adequately reduced in a clinically relevant time period has the potential to transiently suppress recurrent seizures, but additional mechanisms need to be targeted to permanently prevent epilepsy development. Significance Statement: Consistent with morphological and electrophysiological studies suggesting aberrant adult-generated neurons contribute to epilepsy development, ablation of seizure-induced new neurons at the time of the initial insult reduces the frequency of recurrent seizures. In this study, we show that continuous targeting of post-insult new neurons in a therapeutically relevant time period reduces chronic seizures; however, this effect does not persist suggesting possible additional mechanisms.
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19
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Christian KM, Ming GL, Song H. Adult neurogenesis and the dentate gyrus: Predicting function from form. Behav Brain Res 2019; 379:112346. [PMID: 31722241 DOI: 10.1016/j.bbr.2019.112346] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 11/05/2019] [Accepted: 11/05/2019] [Indexed: 12/11/2022]
Abstract
Hypotheses about the functional properties of the dentate gyrus and adult dentate neurogenesis have been shaped by early observations of the anatomy of this region, mostly in rodents. This has led to the development of a few core propositions that have guided research over the past several years, including the predicted role of this region in pattern separation and the local transformation of inputs from the entorhinal cortex. We now have the opportunity to review these predictions and update these anatomical observations based on recently developed techniques that reveal the complex structure, connectivity, and dynamic properties of distinct cell populations in the dentate gyrus at a higher resolution. Cumulative evidence suggests that the dentate gyrus and adult-born granule cells play a role in some forms of behavioral discriminations, but there are still many unanswered questions about how the dentate gyrus processes information to support the disambiguation of stimuli.
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Affiliation(s)
- Kimberly M Christian
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA, 19104, USA; Mahoney Institute for Neurosciences, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Guo-Li Ming
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA, 19104, USA; Mahoney Institute for Neurosciences, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Developmental and Cell Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Epigenetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hongjun Song
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA, 19104, USA; Mahoney Institute for Neurosciences, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Developmental and Cell Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Epigenetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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20
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Miller SM, Sahay A. Functions of adult-born neurons in hippocampal memory interference and indexing. Nat Neurosci 2019; 22:1565-1575. [PMID: 31477897 DOI: 10.1038/s41593-019-0484-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 07/30/2019] [Indexed: 12/22/2022]
Abstract
The dentate gyrus-CA3 circuit of the hippocampus is continuously modified by the integration of adult-born dentate granule cells (abDGCs). All abDGCs undergo a prolonged period of maturation, during which they exhibit heightened synaptic plasticity and refinement of electrophysiological properties and connectivity. Consistent with theoretical models and the known functions of the dentate gyrus-CA3 circuit, acute or chronic manipulations of abDGCs support a role for abDGCs in the regulation of memory interference. In this Review, we integrate insights from studies that examine the maturation of abDGCs and their integration into the circuit with network mechanisms that support memory discrimination, consolidation and clearance. We propose that adult hippocampal neurogenesis enables the generation of a library of experiences, each registered in mature abDGC physiology and connectivity. Mature abDGCs recruit inhibitory microcircuits to support pattern separation and memory indexing.
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Affiliation(s)
- Samara M Miller
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Stem Cell Institute, Cambridge, Massachusetts, USA.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA. .,Harvard Stem Cell Institute, Cambridge, Massachusetts, USA. .,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. .,BROAD Institute of Harvard and MIT, Cambridge, Massachusetts, USA.
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21
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Jain S, LaFrancois JJ, Botterill JJ, Alcantara-Gonzalez D, Scharfman HE. Adult neurogenesis in the mouse dentate gyrus protects the hippocampus from neuronal injury following severe seizures. Hippocampus 2019; 29:683-709. [PMID: 30672046 PMCID: PMC6640126 DOI: 10.1002/hipo.23062] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 10/29/2018] [Accepted: 11/30/2018] [Indexed: 01/20/2023]
Abstract
Previous studies suggest that reducing the numbers of adult-born neurons in the dentate gyrus (DG) of the mouse increases susceptibility to severe continuous seizures (status epilepticus; SE) evoked by systemic injection of the convulsant kainic acid (KA). However, it was not clear if the results would be the same for other ways to induce seizures, or if SE-induced damage would be affected. Therefore, we used pilocarpine, which induces seizures by a different mechanism than KA. Also, we quantified hippocampal damage after SE. In addition, we used both loss-of-function and gain-of-function methods in adult mice. We hypothesized that after loss-of-function, mice would be more susceptible to pilocarpine-induced SE and SE-associated hippocampal damage, and after gain-of-function, mice would be more protected from SE and hippocampal damage after SE. For loss-of-function, adult neurogenesis was suppressed by pharmacogenetic deletion of dividing radial glial precursors. For gain-of-function, adult neurogenesis was increased by conditional deletion of pro-apoptotic gene Bax in Nestin-expressing progenitors. Fluoro-Jade C (FJ-C) was used to quantify neuronal injury and video-electroencephalography (video-EEG) was used to quantify SE. Pilocarpine-induced SE was longer in mice with reduced adult neurogenesis, SE had more power and neuronal damage was greater. Conversely, mice with increased adult-born neurons had shorter SE, SE had less power, and there was less neuronal damage. The results suggest that adult-born neurons exert protective effects against SE and SE-induced neuronal injury.
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Affiliation(s)
- Swati Jain
- Center for Dementia Research, The Nathan Kline Institute of Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA
| | - John J. LaFrancois
- Center for Dementia Research, The Nathan Kline Institute of Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA
| | - Justin J. Botterill
- Center for Dementia Research, The Nathan Kline Institute of Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA
| | - David Alcantara-Gonzalez
- Center for Dementia Research, The Nathan Kline Institute of Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA
| | - Helen E. Scharfman
- Center for Dementia Research, The Nathan Kline Institute of Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA
- Departments of Child & Adolescent Psychiatry, Neuroscience & Physiology, and Psychiatry, New York Langone Medical Center, New York, NY 10016, USA
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22
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Rodríguez-Iglesias N, Sierra A, Valero J. Rewiring of Memory Circuits: Connecting Adult Newborn Neurons With the Help of Microglia. Front Cell Dev Biol 2019; 7:24. [PMID: 30891446 PMCID: PMC6411767 DOI: 10.3389/fcell.2019.00024] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/08/2019] [Indexed: 12/16/2022] Open
Abstract
New neurons are continuously generated from stem cells and integrated into the adult hippocampal circuitry, contributing to memory function. Several environmental, cellular, and molecular factors regulate the formation of new neurons, but the mechanisms that govern their incorporation into memory circuits are less explored. Herein we will focus on microglia, the resident immune cells of the CNS, which modulate the production of new neurons in the adult hippocampus and are also well suited to participate in their circuit integration. Microglia may contribute to the refinement of brain circuits during development and exert a role in physiological and pathological conditions by regulating axonal and dendritic growth; promoting the formation, elimination, and relocation of synapses; modulating excitatory synaptic maturation; and participating in functional synaptic plasticity. Importantly, microglia are able to sense subtle changes in their environment and may use this information to differently modulate hippocampal wiring, ultimately impacting on memory function. Deciphering the role of microglia in hippocampal circuitry constant rewiring will help to better understand the influence of microglia on memory function.
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Affiliation(s)
- Noelia Rodríguez-Iglesias
- Laboratory of Glial Cell Biology, Achucarro Basque Center for Neuroscience, Leioa, Spain.,Department of Neuroscience, University of the Basque Country UPV/EHU, Leioa, Spain
| | - Amanda Sierra
- Laboratory of Glial Cell Biology, Achucarro Basque Center for Neuroscience, Leioa, Spain.,Department of Neuroscience, University of the Basque Country UPV/EHU, Leioa, Spain.,Ikerbasque Foundation, Bilbao, Spain
| | - Jorge Valero
- Laboratory of Glial Cell Biology, Achucarro Basque Center for Neuroscience, Leioa, Spain.,Department of Neuroscience, University of the Basque Country UPV/EHU, Leioa, Spain.,Ikerbasque Foundation, Bilbao, Spain
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Colín-Castelán D, Zaina S. Associations between atherosclerosis and neurological diseases, beyond ischemia-induced cerebral damage. Rev Endocr Metab Disord 2019; 20:15-25. [PMID: 30891682 DOI: 10.1007/s11154-019-09486-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Neurodegeneration is traditionally viewed as a consequence of peptide accumulation in the brain, stroke and/or cerebral ischemia. Nonetheless, a number of scattered observations suggest that neurological disease and atherosclerosis may be linked by more complex mechanisms. Understanding the intricate link between atherosclerosis and neurological conditions may have a significant impact on the quality of life of the growing ageing population and of high cardiovascular risk groups in general. Epidemiological data support the notion that neurological dysfunction and atherosclerosis coexist long before any evident clinical complications of cardiovascular disease appear and may be causally linked. Baffling, often overlooked, molecular data suggest that nervous tissue-specific gene expression is relaxed specifically in the atheromatous vascular wall, and/or that a systemic dysregulation of genes involved in nervous system biology dictates a concomitant progression of neurological disease and atherosclerosis. Further epidemiological and experimental work is needed to clarify the details and clinical relevance of those complex links.
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Affiliation(s)
- Dannia Colín-Castelán
- Department of Medical Sciences, Division of Health Sciences, Campus León, University of Guanajuato, León, Guanajuato, Mexico.
| | - Silvio Zaina
- Department of Medical Sciences, Division of Health Sciences, Campus León, University of Guanajuato, León, Guanajuato, Mexico
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Brydges NM, Moon A, Rule L, Watkin H, Thomas KL, Hall J. Sex specific effects of pre-pubertal stress on hippocampal neurogenesis and behaviour. Transl Psychiatry 2018; 8:271. [PMID: 30531788 PMCID: PMC6288078 DOI: 10.1038/s41398-018-0322-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 11/08/2018] [Accepted: 11/13/2018] [Indexed: 12/13/2022] Open
Abstract
Experience of traumatic events in childhood is linked to an elevated risk of developing psychiatric disorders in adulthood. The neurobiological mechanisms underlying this phenomenon are not fully understood. The limbic system, particularly the hippocampus, is significantly impacted by childhood trauma. In particular, it has been hypothesised that childhood stress may impact adult hippocampal neurogenesis (AHN) and related behaviours, conferring increased risk for later mental illness. Stress in utero can lead to impaired hippocampal synaptic plasticity, and stress in the first 2-3 weeks of life reduces AHN in animal models. Less is known about the effects of stress in the post-weaning, pre-pubertal phase, a developmental time-point more akin to human childhood. Therefore, we investigated persistent effects of pre-pubertal stress (PPS) on functional and molecular aspects of the hippocampus. AHN was altered following PPS in male rats only. Specifically males showed reduced production of new neurons following PPS, but increased survival in the ventral dentate gyrus. In adult males, but not females, pattern separation and trace fear conditioning, behaviours that rely heavily on AHN, were also impaired after PPS. PPS also increased the expression of parvalbumin-positive GABAergic interneurons in the ventral dentate gyrus and increased glutamic acid decarboxylase 67 expression in the ventral hilus, in males only. Our results demonstrate the lasting effects of PPS on the hippocampus in a sex- and time-dependent manner, provide a potential mechanistic link between PPS and later behavioural impairments, and highlight sex differences in vulnerability to neuropsychiatric conditions after early-life stress.
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Affiliation(s)
- Nichola Marie Brydges
- Neuroscience and Mental Health Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ, UK.
| | - Anna Moon
- 0000 0001 0807 5670grid.5600.3Neuroscience and Mental Health Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ UK
| | - Lowenna Rule
- 0000 0001 0807 5670grid.5600.3Neuroscience and Mental Health Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ UK
| | - Holly Watkin
- 0000 0001 0807 5670grid.5600.3Neuroscience and Mental Health Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ UK
| | - Kerrie L. Thomas
- 0000 0001 0807 5670grid.5600.3Neuroscience and Mental Health Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ UK ,0000 0001 0807 5670grid.5600.3School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX UK
| | - Jeremy Hall
- 0000 0001 0807 5670grid.5600.3Neuroscience and Mental Health Research Institute, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ UK ,0000 0001 0807 5670grid.5600.3MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, CF24 4HQ UK
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25
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Dutta RR, Taffe MA, Mandyam CD. Chronic administration of amphetamines disturbs development of neural progenitor cells in young adult nonhuman primates. Prog Neuropsychopharmacol Biol Psychiatry 2018; 85:46-53. [PMID: 29601895 PMCID: PMC5962428 DOI: 10.1016/j.pnpbp.2018.03.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 03/24/2018] [Accepted: 03/25/2018] [Indexed: 02/07/2023]
Abstract
The detrimental effects of amphetamines on developmental stages of NPCs are limited to rodent brain and it is not known if these effects occur in nonhuman primates which are the focus of the current investigation. Young adult rhesus macaques either experienced MDMA only, a combination of amphetamines (MDMA, MDA and methamphetamine) or no amphetamines (controls) and hippocampal tissue was processed for immunohistochemical analysis.Quantitative stereological analysis showed that intermittent exposure to MDMA or the three amphetamines over 9.6 months causes >80% decrease in the number of Ki-67 cells (actively dividing NPCs) and >50% decrease in the number of NeuroD1 cells (NPCs that have attained a neuronal phenotype). Co-labeling analysis revealed distinct, actively dividing hippocampal NPCs in the subgranular zone of the dentate gyrus that were in transition from stem-like radial glia-like cells (type-1) to immature transiently amplifying neuroblasts (type-2a, type-2b, and type-3).MDMA-alone and the combination reduced the number of dividing type-1 and type-3 NPCs and cells that were not NPCs. These data indicate that amphetamines interfere with the division and migration of NPCs. Notably, the reduction in the number of NPCs and immature neurons were not associated with changes in cell death (via apoptosis) or granule cell neuron numbers, indicating that amphetamines selectively affected the generation and maturation of newly born granule cell neurons. In sum, our findings suggest that alterations in the cellular composition in the dentate gyrus during chronic exposure to amphetamines can effect neuroplasticity in the hippocampus and influence functional properties of hippocampal neurons.
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Affiliation(s)
- Rahul R Dutta
- Department of Neuroscience, The Scripps Research Institute,USA
| | - Michael A Taffe
- Department of Neuroscience, The Scripps Research Institute,USA
| | - Chitra D Mandyam
- Department of Neuroscience, The Scripps Research Institute,USA; VA San Diego Healthcare System, USA; Department of Anesthesiology, University of California San Diego, San Diego, CA, USA.
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26
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Baptista P, Andrade JP. Adult Hippocampal Neurogenesis: Regulation and Possible Functional and Clinical Correlates. Front Neuroanat 2018; 12:44. [PMID: 29922131 PMCID: PMC5996050 DOI: 10.3389/fnana.2018.00044] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 05/11/2018] [Indexed: 01/19/2023] Open
Abstract
The formation of new neurons in the adult central nervous system (CNS) has been recognized as one of the major findings in neuroanatomical research. The hippocampal formation (HF), one of the main targets of these investigations, holds a neurogenic niche widely recognized among several mammalian species and whose existence in the human brain has sparked controversy and extensive debate. Many cellular features from this region emphasize that hippocampal neurogenesis suffers changes with normal aging and, among regulatory factors, physical exercise and chronic stress provoke opposite effects on cell proliferation, maturation and survival. Considering the numerous functions attributable to the HF, increasing or decreasing the integration of new neurons in the delicate neuronal network might be significant for modulation of cognition and emotion. The role that immature and mature adult-born neurons play in this circuitry is still mostly unknown but it could prove fundamental to understand hippocampal-dependent cognitive processes, the pathophysiology of depression, and the therapeutic effects of antidepressant medication in modulating behavior and mental health.
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Affiliation(s)
- Pedro Baptista
- Unit of Anatomy, Department of Biomedicine, Faculty of Medicine of University of Porto, Porto, Portugal
| | - José P Andrade
- Unit of Anatomy, Department of Biomedicine, Faculty of Medicine of University of Porto, Porto, Portugal.,Center of Health Technology and Services Research (CINTESIS), Faculty of Medicine of University of Porto, Porto, Portugal
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27
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Beyond good and evil: A putative continuum-sorting hypothesis for the functional role of proBDNF/BDNF-propeptide/mBDNF in antidepressant treatment. Neurosci Biobehav Rev 2018; 90:70-83. [PMID: 29626490 DOI: 10.1016/j.neubiorev.2018.04.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 03/13/2018] [Accepted: 04/03/2018] [Indexed: 02/07/2023]
Abstract
Depression and posttraumatic stress disorder are assumed to be maladaptive responses to stress and antidepressants are thought to counteract such responses by increasing BDNF (brain-derived neurotrophic factor) levels. BDNF acts through TrkB (tropomyosin-related receptor kinase B) and plays a central role in neuroplasticity. In contrast, both precursor proBDNF and BDNF propeptide (another metabolic product from proBDNF cleavage) have a high affinity to p75 receptor (p75R) and usually convey apoptosis and neuronal shrinkage. Although BDNF and proBDNF/propeptide apparently act in opposite ways, neuronal turnover and remodeling might be a final common way that both act to promote more effective neuronal networking, avoiding neuronal redundancy and the misleading effects of environmental contingencies. This review aims to provide a brief overview about the BDNF functional role in antidepressant action and about p75R and TrkB signaling to introduce the "continuum-sorting hypothesis." The resulting hypothesis suggests that both BDNF/proBDNF and BDNF/propeptide act as protagonists to fine-tune antidepressant-dependent neuroplasticity in crucial brain structures to modulate behavioral responses to stress.
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Comparison of Adult Hippocampal Neurogenesis and Susceptibility to Treadmill Exercise in Nine Mouse Strains. Neural Plast 2017; 2017:5863258. [PMID: 29391953 PMCID: PMC5748094 DOI: 10.1155/2017/5863258] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/22/2017] [Accepted: 04/11/2017] [Indexed: 12/13/2022] Open
Abstract
The genetic background of mice has various influences on the efficacy of physical exercise, as well as adult neurogenesis in the hippocampus. In this study, we investigated the basal level of hippocampal neurogenesis, as well as the effects of treadmill exercise on adult hippocampal neurogenesis in 9 mouse strains: 8 very commonly used laboratory inbred mouse strains (C57BL/6, BALB/c, A/J, C3H/HeJ, DBA/1, DBA/2, 129/SvJ, and FVB) and 1 outbred mouse strain (ICR). All 9 strains showed diverse basal levels of cell proliferation, neuroblast differentiation, and integration into granule cells in the sedentary group. C57BL/6 mice showed the highest levels of cell proliferation, neuroblast differentiation, and integration into granule cells at basal levels, and the DBA/2 mice showed the lowest levels. The efficacy of integration into granule cells was maximal in ICR mice. Treadmill exercise increased adult hippocampal neurogenesis in all 9 mouse strains. These results suggest that the genetic background of mice affects hippocampal neurogenesis and C57BL/6 mice are the most useful strain to assess basal levels of cell proliferation and neuroblast differentiation, but not maturation into granule cells. In addition, the DBA/2 strain is not suitable for studying hippocampal neurogenesis.
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Abstract
Millions of individuals suffer from age-related cognitive decline, defined by impaired memory precision. Increased understanding of hippocampal circuit mechanisms underlying memory formation suggests a role for computational processes such as pattern separation and pattern completion in memory precision. We describe evidence implicating the dentate gyrus-CA3 circuit in pattern separation and completion, and examine alterations in dentate gyrus-CA3 circuit structure and function with aging. We discuss the role of adult hippocampal neurogenesis in memory precision in adulthood and aging, as well as the circuit mechanisms underlying the integration and encoding functions of adult-born dentate granule cells. We posit that understanding these circuit mechanisms will permit generation of circuit-based endophenotypes that will edify new therapeutic strategies to optimize hippocampal encoding during aging.
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Affiliation(s)
- Kathleen M McAvoy
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Harvard Stem Cell Institute, Cambridge, MA, 02138, USA
- Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA.
- Harvard Stem Cell Institute, Cambridge, MA, 02138, USA.
- Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA.
- BROAD Institute of Harvard and MIT, Cambridge, MA, 02142, USA.
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30
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Abstract
Adult hippocampal neurogenesis (AHN) occurs in humans and every other mammalian species examined. Evidence that AHN is stimulated by a variety of treatments and behaviors with anxiolytic properties has sparked interest in harnessing AHN to treat anxiety disorders. However, relatively little is known about the mechanisms through which AHN modulates fear and anxiety. In this review, we consider evidence that AHN modulates fear and anxiety by altering the processing of and memory for traumatic experiences. Based on studies of the role of AHN in Pavlovian fear conditioning, we conclude that AHN modulates the consequences of aversive experience by influencing 1) the efficiency of hippocampus-dependent memory acquisition; 2) generalization of hippocampal fear memories; 3) long-term retention of hippocampal aversive memories; and 4) the nonassociative effects of acute aversive experience. The preclinical literature suggests that stimulation of AHN is likely to have therapeutically relevant consequences, including reduced generalization and long-term retention of aversive memories. However, the literature also identifies four caveats that must be addressed if AHN-based therapies are to achieve therapeutic benefits without significant side effects.
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Affiliation(s)
- Michael R Drew
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, USA.
| | - Kylie A Huckleberry
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
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31
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Anacker C, Hen R. Adult hippocampal neurogenesis and cognitive flexibility - linking memory and mood. Nat Rev Neurosci 2017; 18:335-346. [PMID: 28469276 DOI: 10.1038/nrn.2017.45] [Citation(s) in RCA: 615] [Impact Index Per Article: 87.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Adult hippocampal neurogenesis has been implicated in cognitive processes, such as pattern separation, and in the behavioural effects of stress and antidepressants. Young adult-born neurons have been shown to inhibit the overall activity of the dentate gyrus by recruiting local interneurons, which may result in sparse contextual representations and improved pattern separation. We propose that neurogenesis-mediated inhibition also reduces memory interference and enables reversal learning both in neutral situations and in emotionally charged ones. Such improved cognitive flexibility may in turn help to decrease anxiety-like and depressive-like behaviour.
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Affiliation(s)
- Christoph Anacker
- Department of Psychiatry, Columbia University and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, 1051 Riverside Drive, New York 10032, New York, USA
| | - René Hen
- Department of Psychiatry, Columbia University and Research Foundation for Mental Hygiene, New York State Psychiatric Institute, 1051 Riverside Drive, New York 10032, New York, USA.,Department of Neuroscience, Columbia University, Kolb Annex, 40 Haven Ave, New York 10032, New York, USA.,Department of Pharmacology, Columbia University, 630 West 168th Street, New York 10032, New York, USA
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32
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Becker S. Neurogenesis and pattern separation: time for a divorce. WILEY INTERDISCIPLINARY REVIEWS. COGNITIVE SCIENCE 2016; 8. [PMID: 28026915 DOI: 10.1002/wcs.1427] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 09/09/2016] [Accepted: 09/30/2016] [Indexed: 01/08/2023]
Abstract
The generation of new neurons in the adult mammalian brain has led to numerous theories as to their functional significance. One of the most widely held views is that adult neurogenesis promotes pattern separation, a process by which overlapping patterns of neural activation are mapped to less overlapping representations. While a large body of evidence supports a role for neurogenesis in high interference memory tasks, it does not support the proposed function of neurogenesis in mediating pattern separation. Instead, the adult-generated neurons seem to generate highly overlapping and yet distinct distributed representations for similar events. One way in which these immature, highly plastic, hyperactive neurons may contribute to novel memory formation while avoiding interference is by virtue of their extremely sparse connectivity with incoming perforant path fibers. Another intriguing proposal, awaiting empirical confirmation, is that the young neurons' recruitment into memory formation is gated by a novelty/mismatch mechanism mediated by CA3 or hilar back-projections. Ongoing research into the intriguing link between neurogenesis, stress-related mood disorders, and age-related neurodegeneration may lead to promising neurogenesis-based treatments for this wide range of clinical disorders. WIREs Cogn Sci 2017, 8:e1427. doi: 10.1002/wcs.1427 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Suzanna Becker
- Department of Psychology Neuroscience and Behaviour, McMaster University, Hamilton, Canada
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33
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Sweet TB, Hurley SD, Wu MD, Olschowka JA, Williams JP, O'Banion MK. Neurogenic Effects of Low-Dose Whole-Body HZE (Fe) Ion and Gamma Irradiation. Radiat Res 2016; 186:614-623. [PMID: 27905869 DOI: 10.1667/rr14530.1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Understanding the dose-toxicity profile of radiation is critical when evaluating potential health risks associated with natural and man-made sources in our environment. The purpose of this study was to evaluate the effects of low-dose whole-body high-energy charged (HZE) iron (Fe) ions and low-energy gamma exposure on proliferation and differentiation of adult-born neurons within the dentate gyrus of the hippocampus, cells deemed to play a critical role in memory regulation. To determine the dose-response characteristics of the brain to whole-body Fe-ion vs. gamma-radiation exposure, C57BL/6J mice were irradiated with 1 GeV/n Fe ions or a static 137Cs source (0.662 MeV) at doses ranging from 0 to 300 cGy. The neurogenesis was analyzed at 48 h and one month postirradiation. These experiments revealed that whole-body exposure to either Fe ions or gamma radiation leads to: 1. An acute decrease in cell division within the dentate gyrus of the hippocampus, detected at doses as low as 30 and 100 cGy for Fe ions and gamma radiation, respectively; and 2. A reduction in newly differentiated neurons (DCX immunoreactivity) at one month postirradiation, with significant decreases detected at doses as low as 100 cGy for both Fe ions and gamma rays. The data presented here contribute to our understanding of brain responses to whole-body Fe ions and gamma rays and may help inform health-risk evaluations related to systemic exposure during a medical or radiologic/nuclear event or as a result of prolonged space travel.
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Affiliation(s)
- Tara B Sweet
- aDepartment of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Sean D Hurley
- aDepartment of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Michael D Wu
- aDepartment of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - John A Olschowka
- aDepartment of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Jacqueline P Williams
- b Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642.,c Department of Radiation Oncology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - M Kerry O'Banion
- aDepartment of Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642.,d Neurology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
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McAvoy KM, Scobie KN, Berger S, Russo C, Guo N, Decharatanachart P, Vega-Ramirez H, Miake-Lye S, Whalen M, Nelson M, Bergami M, Bartsch D, Hen R, Berninger B, Sahay A. Modulating Neuronal Competition Dynamics in the Dentate Gyrus to Rejuvenate Aging Memory Circuits. Neuron 2016; 91:1356-1373. [PMID: 27593178 DOI: 10.1016/j.neuron.2016.08.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 05/19/2016] [Accepted: 08/01/2016] [Indexed: 12/23/2022]
Abstract
The neural circuit mechanisms underlying the integration and functions of adult-born dentate granule cell (DGCs) are poorly understood. Adult-born DGCs are thought to compete with mature DGCs for inputs to integrate. Transient genetic overexpression of a negative regulator of dendritic spines, Kruppel-like factor 9 (Klf9), in mature DGCs enhanced integration of adult-born DGCs and increased NSC activation. Reversal of Klf9 overexpression in mature DGCs restored spines and activity and reset neuronal competition dynamics and NSC activation, leaving the DG modified by a functionally integrated, expanded cohort of age-matched adult-born DGCs. Spine elimination by inducible deletion of Rac1 in mature DGCs increased survival of adult-born DGCs without affecting proliferation or DGC activity. Enhanced integration of adult-born DGCs transiently reorganized adult-born DGC local afferent connectivity and promoted global remapping in the DG. Rejuvenation of the DG by enhancing integration of adult-born DGCs in adulthood, middle age, and aging enhanced memory precision.
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Affiliation(s)
- Kathleen M McAvoy
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA; Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 USA
| | - Kimberly N Scobie
- Departments of Neuroscience and Psychiatry, Columbia University, New York, NY 10032, USA
| | - Stefan Berger
- Department of Molecular Biology, Central Institute of Mental Health and Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Craig Russo
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA
| | - Nannan Guo
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA; Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 USA
| | | | - Hugo Vega-Ramirez
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA; Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 USA
| | - Sam Miake-Lye
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Michael Whalen
- Neuroscience Center, Massachusetts General Hospital, Boston, MA 02129, USA
| | - Mark Nelson
- Echelon Biosciences, Salt Lake City, UT 84108, USA
| | - Matteo Bergami
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and University Hospital of Cologne, Joseph-Stelzmann-Straße 26, D-50931 Cologne, Germany
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health and Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Rene Hen
- Departments of Neuroscience and Psychiatry, Columbia University, New York, NY 10032, USA
| | - Benedikt Berninger
- Institute of Physiological Chemistry, University Medical Center Johannes Gutenberg University, 55128 Mainz, Germany
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA; Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
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35
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Upadhya D, Hattiangady B, Shetty GA, Zanirati G, Kodali M, Shetty AK. Neural Stem Cell or Human Induced Pluripotent Stem Cell-Derived GABA-ergic Progenitor Cell Grafting in an Animal Model of Chronic Temporal Lobe Epilepsy. CURRENT PROTOCOLS IN STEM CELL BIOLOGY 2016; 38:2D.7.1-2D.7.47. [PMID: 27532817 PMCID: PMC5313261 DOI: 10.1002/cpsc.9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Grafting of neural stem cells (NSCs) or GABA-ergic progenitor cells (GPCs) into the hippocampus could offer an alternative therapy to hippocampal resection in patients with drug-resistant chronic epilepsy, which afflicts >30% of temporal lobe epilepsy (TLE) cases. Multipotent, self-renewing NSCs could be expanded from multiple regions of the developing and adult brain, human embryonic stem cells (hESCs), and human induced pluripotent stem cells (hiPSCs). On the other hand, GPCs could be generated from the medial and lateral ganglionic eminences of the embryonic brain and from hESCs and hiPSCs. To provide comprehensive methodologies involved in testing the efficacy of transplantation of NSCs and GPCs in a rat model of chronic TLE, NSCs derived from the rat medial ganglionic eminence (MGE) and MGE-like GPCs derived from hiPSCs are taken as examples in this unit. The topics comprise description of the required materials, reagents and equipment, methods for obtaining rat MGE-NSCs and hiPSC-derived MGE-like GPCs in culture, generation of chronically epileptic rats, intrahippocampal grafting procedure, post-grafting evaluation of the effects of grafts on spontaneous recurrent seizures and cognitive and mood impairments, analyses of the yield and the fate of graft-derived cells, and the effects of grafts on the host hippocampus. © 2016 by John Wiley & Sons, Inc.
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Affiliation(s)
- Dinesh Upadhya
- Institute for Regenerative Medicine, Texas A&M University Health Science Center College of Medicine, Temple, Texas
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, Temple, Texas
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center College of Medicine, College Station, Texas
| | - Bharathi Hattiangady
- Institute for Regenerative Medicine, Texas A&M University Health Science Center College of Medicine, Temple, Texas
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, Temple, Texas
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center College of Medicine, College Station, Texas
| | - Geetha A Shetty
- Institute for Regenerative Medicine, Texas A&M University Health Science Center College of Medicine, Temple, Texas
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, Temple, Texas
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center College of Medicine, College Station, Texas
| | - Gabriele Zanirati
- Institute for Regenerative Medicine, Texas A&M University Health Science Center College of Medicine, Temple, Texas
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center College of Medicine, College Station, Texas
| | - Maheedhar Kodali
- Institute for Regenerative Medicine, Texas A&M University Health Science Center College of Medicine, Temple, Texas
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, Temple, Texas
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center College of Medicine, College Station, Texas
| | - Ashok K Shetty
- Institute for Regenerative Medicine, Texas A&M University Health Science Center College of Medicine, Temple, Texas
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, Temple, Texas
- Department of Molecular and Cellular Medicine, Texas A&M University Health Science Center College of Medicine, College Station, Texas
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36
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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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Sosa M, Gillespie AK, Frank LM. Neural Activity Patterns Underlying Spatial Coding in the Hippocampus. Curr Top Behav Neurosci 2016; 37:43-100. [PMID: 27885550 DOI: 10.1007/7854_2016_462] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The hippocampus is well known as a central site for memory processing-critical for storing and later retrieving the experiences events of daily life so they can be used to shape future behavior. Much of what we know about the physiology underlying hippocampal function comes from spatial navigation studies in rodents, which have allowed great strides in understanding how the hippocampus represents experience at the cellular level. However, it remains a challenge to reconcile our knowledge of spatial encoding in the hippocampus with its demonstrated role in memory-dependent tasks in both humans and other animals. Moreover, our understanding of how networks of neurons coordinate their activity within and across hippocampal subregions to enable the encoding, consolidation, and retrieval of memories is incomplete. In this chapter, we explore how information may be represented at the cellular level and processed via coordinated patterns of activity throughout the subregions of the hippocampal network.
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Affiliation(s)
- Marielena Sosa
- Kavli Institute for Fundamental Neuroscience and Department of Physiology, University of California, San Francisco, USA
| | | | - Loren M Frank
- Kavli Institute for Fundamental Neuroscience and Department of Physiology, University of California, San Francisco, USA. .,Howard Hughes Medical Institute, Maryland, USA.
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Vivar C, Peterson BD, van Praag H. Running rewires the neuronal network of adult-born dentate granule cells. Neuroimage 2015; 131:29-41. [PMID: 26589333 DOI: 10.1016/j.neuroimage.2015.11.031] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 11/11/2015] [Accepted: 11/12/2015] [Indexed: 01/06/2023] Open
Abstract
Exercise improves cognition in humans and animals. Running increases neurogenesis in the dentate gyrus of the hippocampus, a brain area important for learning and memory. It is unclear how running modifies the circuitry of new dentate gyrus neurons to support their role in memory function. Here we combine retroviral labeling with rabies virus mediated trans-synaptic retrograde tracing to define and quantify new neuron afferent inputs in young adult male C57Bl/6 mice, housed with or without a running wheel for one month. Exercise resulted in a shift in new neuron networks that may promote sparse encoding and pattern separation. Neurogenesis increased in the dorsal, but not the ventral, dentate gyrus by three-fold, whereas afferent traced cell labeling doubled in number. Regional analysis indicated that running differentially affected specific inputs. Within the hippocampus the ratio of innervation from inhibitory interneurons and glutamatergic mossy cells to new neurons was reduced. Distal traced cells were located in sub-cortical and cortical regions, including perirhinal, entorhinal and sensory cortices. Innervation from entorhinal cortex (EC) was augmented, in proportion to the running-induced enhancement of adult neurogenesis. Within EC afferent input and short-term synaptic plasticity from lateral entorhinal cortex, considered to convey contextual information to the hippocampus was increased. Furthermore, running upregulated innervation from regions important for spatial memory and theta rhythm generation, including caudo-medial entorhinal cortex and subcortical medial septum, supra- and medial mammillary nuclei. Altogether, running may facilitate contextual, spatial and temporal information encoding by increasing adult hippocampal neurogenesis and by reorganization of new neuron circuitry.
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Affiliation(s)
- Carmen Vivar
- Neuroplasticity and Behavior Unit, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, United States
| | - Benjamin D Peterson
- Neuroplasticity and Behavior Unit, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, United States
| | - Henriette van Praag
- Neuroplasticity and Behavior Unit, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, United States.
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Finnegan R, Becker S. Neurogenesis paradoxically decreases both pattern separation and memory interference. Front Syst Neurosci 2015; 9:136. [PMID: 26500511 PMCID: PMC4593858 DOI: 10.3389/fnsys.2015.00136] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 09/18/2015] [Indexed: 01/01/2023] Open
Abstract
The hippocampus has been the focus of memory research for decades. While the functional role of this structure is not fully understood, it is widely recognized as being vital for rapid yet accurate encoding and retrieval of associative memories. Since the discovery of adult hippocampal neurogenesis in the dentate gyrus by Altman and Das in the 1960's, many theories and models have been put forward to explain the functional role it plays in learning and memory. These models postulate different ways in which new neurons are introduced into the dentate gyrus and their functional importance for learning and memory. Few if any previous models have incorporated the unique properties of young adult-born dentate granule cells and the developmental trajectory. In this paper, we propose a novel computational model of the dentate gyrus that incorporates the developmental trajectory of the adult-born dentate granule cells, including changes in synaptic plasticity, connectivity, excitability and lateral inhibition, using a modified version of the Restricted Boltzmann machine. Our results show superior performance on memory reconstruction tasks for both recent and distally learned items, when the unique characteristics of young dentate granule cells are taken into account. Even though the hyperexcitability of the young neurons generates more overlapping neural codes, reducing pattern separation, the unique properties of the young neurons nonetheless contribute to reducing retroactive and proactive interference, at both short and long time scales. The sparse connectivity is particularly important for generating distinct memory traces for highly overlapping patterns that are learned within the same context.
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Affiliation(s)
- Rory Finnegan
- Neurotechnology and Neuroplasticity Lab, McMaster Integrative Neuroscience Discovery & Study, McMaster University Hamilton, ON, Canada
| | - Suzanna Becker
- Neurotechnology and Neuroplasticity Lab, Department of Psychology, Neuroscience and Behaviour, McMaster University Hamilton, ON, Canada
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