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Morales C, Morici JF, Espinosa N, Sacson A, Lara-Vasquez A, García-Pérez MA, Bekinschtein P, Weisstaub NV, Fuentealba P. Dentate Gyrus Somatostatin Cells are Required for Contextual Discrimination During Episodic Memory Encoding. Cereb Cortex 2021; 31:1046-1059. [PMID: 33026440 DOI: 10.1093/cercor/bhaa273] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 08/24/2020] [Accepted: 08/25/2020] [Indexed: 11/12/2022] Open
Abstract
Memory systems ought to store and discriminate representations of similar experiences in order to efficiently guide future decisions. This problem is solved by pattern separation, implemented in the dentate gyrus (DG) by granule cells to support episodic memory formation. Pattern separation is enabled by tonic inhibitory bombardment generated by multiple GABAergic cell populations that strictly maintain low activity levels in granule cells. Somatostatin-expressing cells are one of those interneuron populations, selectively targeting the distal dendrites of granule cells, where cortical multimodal information reaches the DG. Nonetheless, somatostatin cells have very low connection probability and synaptic efficacy with both granule cells and other interneuron types. Hence, the role of somatostatin cells in DG circuitry, particularly in the context of pattern separation, remains uncertain. Here, by using optogenetic stimulation and behavioral tasks in mice, we demonstrate that somatostatin cells are required for the acquisition of both contextual and spatial overlapping memories.
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Affiliation(s)
- Cristian Morales
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia, Pontificia Universidad Catolica de Chile, Santiago 7820436, Chile
| | - Juan Facundo Morici
- Instituto de Neurociencia Cognitiva y Traslacional, Instituto de Neurologia Cognitiva, Consejo Nacional de Investigaciones Cientificas y Tecnicas Fundacion INECO, Universidad Favaloro, 1078 Buenos Aires, Argentina
| | - Nelson Espinosa
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia, Pontificia Universidad Catolica de Chile, Santiago 7820436, Chile
| | - Agostina Sacson
- Instituto de Neurociencia Cognitiva y Traslacional, Instituto de Neurologia Cognitiva, Consejo Nacional de Investigaciones Cientificas y Tecnicas Fundacion INECO, Universidad Favaloro, 1078 Buenos Aires, Argentina
| | - Ariel Lara-Vasquez
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia, Pontificia Universidad Catolica de Chile, Santiago 7820436, Chile
| | - M A García-Pérez
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia, Pontificia Universidad Catolica de Chile, Santiago 7820436, Chile
| | - Pedro Bekinschtein
- Instituto de Neurociencia Cognitiva y Traslacional, Instituto de Neurologia Cognitiva, Consejo Nacional de Investigaciones Cientificas y Tecnicas Fundacion INECO, Universidad Favaloro, 1078 Buenos Aires, Argentina
| | - Noelia V Weisstaub
- Instituto de Neurociencia Cognitiva y Traslacional, Instituto de Neurologia Cognitiva, Consejo Nacional de Investigaciones Cientificas y Tecnicas Fundacion INECO, Universidad Favaloro, 1078 Buenos Aires, Argentina
| | - Pablo Fuentealba
- Departamento de Psiquiatria, Centro Interdisciplinario de Neurociencia, Pontificia Universidad Catolica de Chile, Santiago 7820436, Chile.,Centro de Investigacion en Nanotecnologia y Materiales Avanzados, Pontificia Universidad Catolica de Chile, Santiago 7820436, Chile
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Dorsoventral and Proximodistal Hippocampal Processing Account for the Influences of Sleep and Context on Memory (Re)consolidation: A Connectionist Model. COMPUTATIONAL INTELLIGENCE AND NEUROSCIENCE 2017; 2017:8091780. [PMID: 28757864 PMCID: PMC5512097 DOI: 10.1155/2017/8091780] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/23/2017] [Accepted: 06/01/2017] [Indexed: 11/23/2022]
Abstract
The context in which learning occurs is sufficient to reconsolidate stored memories and neuronal reactivation may be crucial to memory consolidation during sleep. The mechanisms of context-dependent and sleep-dependent memory (re)consolidation are unknown but involve the hippocampus. We simulated memory (re)consolidation using a connectionist model of the hippocampus that explicitly accounted for its dorsoventral organization and for CA1 proximodistal processing. Replicating human and rodent (re)consolidation studies yielded the following results. (1) Semantic overlap between memory items and extraneous learning was necessary to explain experimental data and depended crucially on the recurrent networks of dorsal but not ventral CA3. (2) Stimulus-free, sleep-induced internal reactivations of memory patterns produced heterogeneous recruitment of memory items and protected memories from subsequent interference. These simulations further suggested that the decrease in memory resilience when subjects were not allowed to sleep following learning was primarily due to extraneous learning. (3) Partial exposure to the learning context during simulated sleep (i.e., targeted memory reactivation) uniformly increased memory item reactivation and enhanced subsequent recall. Altogether, these results show that the dorsoventral and proximodistal organization of the hippocampus may be important components of the neural mechanisms for context-based and sleep-based memory (re)consolidations.
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Leake J, Zinn R, Corbit L, Vissel B. Dissociation between complete hippocampal context memory formation and context fear acquisition. ACTA ACUST UNITED AC 2017; 24:153-157. [PMID: 28298553 PMCID: PMC5362699 DOI: 10.1101/lm.044578.116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 01/20/2017] [Indexed: 11/24/2022]
Abstract
Rodents require a minimal time period to explore a context prior to footshock to display plateau-level context fear at test. To investigate whether this rapid fear plateau reflects complete memory formation within that short time-frame, we used the immediate-early gene product Arc as an indicator of hippocampal context memory formation-related activity. We found that hippocampal Arc expression continued to increase well past the minimal time required for plateau-level fear. This raises the possibility that context fear conditioning occurs more rapidly than complete memory formation. Thus, animals may be able to condition robustly to both complete and incomplete contextual representations.
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Affiliation(s)
- Jessica Leake
- Neurodegenerative Disorders, Neuroscience Department, Garvan Institute of Medical Research, Sydney 2010, Australia.,School of Psychology, The University of Sydney, Sydney 2006, Australia
| | - Raphael Zinn
- Neurodegenerative Disorders, Neuroscience Department, Garvan Institute of Medical Research, Sydney 2010, Australia.,Faculty of Medicine, University of New South Wales, Sydney 2052, Australia.,School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney 2007, Australia
| | - Laura Corbit
- School of Psychology, The University of Sydney, Sydney 2006, Australia
| | - Bryce Vissel
- Neurodegenerative Disorders, Neuroscience Department, Garvan Institute of Medical Research, Sydney 2010, Australia.,Faculty of Medicine, University of New South Wales, Sydney 2052, Australia.,School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney 2007, Australia
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