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Chen X, Cheng N, Wang C, Knierim JJ. Impaired spatial coding of the hippocampus in a dentate gyrus hypoplasia mouse model. Proc Natl Acad Sci U S A 2025; 122:e2416214122. [PMID: 39883841 PMCID: PMC11804539 DOI: 10.1073/pnas.2416214122] [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: 08/12/2024] [Accepted: 12/28/2024] [Indexed: 02/01/2025] Open
Abstract
The hippocampal dentate gyrus (DG) is thought to orthogonalize inputs from the entorhinal cortex (pattern separation) and relay this information to the CA3 region. In turn, attractor dynamics in CA3 perform a pattern completion or error correction operation before sending its output to CA1. In a mouse model of congenital hypoplasia of the DG, a deficiency in the Wntless (Wls) gene, specifically in cells expressing Gfap-Cre, which targets neuronal progenitors, led to an almost total absence of dentate granule cells and modestly impaired performance in spatial tasks. Here, we investigated the physiological consequences of granule cell loss in these mice by conducting in vivo calcium imaging from CA1 principal cells during behavior. The spatial selectivity of these cells was preserved without the DG. On a linear track, place fields in mutant mice were more likely to be near track terminals and to encode the distance from the start point in each running direction. In an open box, CA1 cells in mutant mice exhibited reductions in the percentage of place cells, in spatial information, and in place field stability. The reduction in place field stability across repeated exposures to the same environment resulted in a reduction in the differential representations of two different contexts in mutant mice compared to wild-type mice. These results suggest that DG helps to stabilize CA1 spatial representations, especially in 2-D environments, and that the lack of stability across similar environments may play a key role in the deficits of animals with DG dysfunction in discriminating different environments.
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Affiliation(s)
- Xiaojing Chen
- Brain Research Centre, Department of Neuroscience, School of Life Sciences, Southern University of Science and Technology, Shenzhen518055, China
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD21218
| | - Ning Cheng
- Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen518055, China
| | - Cheng Wang
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD21218
- Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen518055, China
| | - James J. Knierim
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD21218
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD21218
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD21218
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD21218
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2
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Hu Y, Tao W. Current perspectives on microglia-neuron communication in the central nervous system: Direct and indirect modes of interaction. J Adv Res 2024; 66:251-265. [PMID: 38195039 PMCID: PMC11674795 DOI: 10.1016/j.jare.2024.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 10/05/2023] [Accepted: 01/06/2024] [Indexed: 01/11/2024] Open
Abstract
BACKGROUND The incessant communication that takes place between microglia and neurons is essential the development, maintenance, and pathogenesis of the central nervous system (CNS). As mobile phagocytic cells, microglia serve a critical role in surveilling and scavenging the neuronal milieu to uphold homeostasis. AIM OF REVIEW This review aims to discuss the various mechanisms that govern the interaction between microglia and neurons, from the molecular to the organ system level, and to highlight the importance of these interactions in the development, maintenance, and pathogenesis of the CNS. KEY SCIENTIFIC CONCEPTS OF REVIEW Recent research has revealed that microglia-neuron interaction is vital for regulating fundamental neuronal functions, such as synaptic pruning, axonal remodeling, and neurogenesis. The review will elucidate the intricate signaling pathways involved in these interactions, both direct and indirect, to provide a better understanding of the fundamental mechanisms of brain function. Furthermore, gaining insights into these signals could lead to the development of innovative therapies for neural disorders.
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Affiliation(s)
- Yue Hu
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine, Nanjing 220023, China; School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210023, China
| | - Weiwei Tao
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine, Nanjing 220023, China; School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210023, China.
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3
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Zhang CL, Sontag L, Gómez-Ocádiz R, Schmidt-Hieber C. Learning-dependent gating of hippocampal inputs by frontal interneurons. Proc Natl Acad Sci U S A 2024; 121:e2403325121. [PMID: 39467130 PMCID: PMC11551329 DOI: 10.1073/pnas.2403325121] [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: 02/16/2024] [Accepted: 09/03/2024] [Indexed: 10/30/2024] Open
Abstract
The hippocampus is a brain region that is essential for the initial encoding of episodic memories. However, the consolidation of these memories is thought to occur in the neocortex, under guidance of the hippocampus, over the course of days and weeks. Communication between the hippocampus and the neocortex during hippocampal sharp wave-ripple oscillations is believed to be critical for this memory consolidation process. Yet, the synaptic and circuit basis of this communication between brain areas is largely unclear. To address this problem, we perform in vivo whole-cell patch-clamp recordings in the frontal neocortex and local field potential recordings in CA1 of head-fixed mice exposed to a virtual-reality environment. In mice trained in a goal-directed spatial task, we observe a depolarization in frontal principal neurons during hippocampal ripple oscillations. Both this ripple-associated depolarization and goal-directed task performance can be disrupted by chemogenetic inactivation of somatostatin-positive (SOM+) interneurons. In untrained mice, a ripple-associated depolarization is not observed, but it emerges when frontal parvalbumin-positive (PV+) interneurons are inactivated. These results support a model where SOM+ interneurons inhibit PV+ interneurons during hippocampal activity, thereby acting as a disinhibitory gate for hippocampal inputs to neocortical principal neurons during learning.
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Affiliation(s)
- Chun-Lei Zhang
- Institut Pasteur, Université Paris Cité, Neural Circuits for Space and Memory, Department of Neuroscience, ParisF-75015, France
| | - Lucile Sontag
- Institut Pasteur, Université Paris Cité, Neural Circuits for Space and Memory, Department of Neuroscience, ParisF-75015, France
| | - Ruy Gómez-Ocádiz
- Institut Pasteur, Université Paris Cité, Neural Circuits for Space and Memory, Department of Neuroscience, ParisF-75015, France
| | - Christoph Schmidt-Hieber
- Institut Pasteur, Université Paris Cité, Neural Circuits for Space and Memory, Department of Neuroscience, ParisF-75015, France
- Institute for Physiology I, Jena University Hospital, Jena07743, Germany
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4
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Mitchnick KA, Labardo S, Rosenbaum RS. Dissociations in perceptual discrimination following selective damage to the dentate gyrus versus CA1 subfield of the hippocampus. Cortex 2024; 179:191-214. [PMID: 39197409 DOI: 10.1016/j.cortex.2024.06.020] [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: 08/04/2023] [Revised: 12/03/2023] [Accepted: 06/05/2024] [Indexed: 09/01/2024]
Abstract
The hippocampus (HPC) is well-known for its involvement in declarative (consciously accessible) memory, but there is evidence that it may also play a role in complex perceptual discrimination. Separate research has demonstrated separable contributions of HPC subregions to component memory processes, with the dentate gyrus (DG) required for mnemonic discrimination of similar inputs and the CA1 subfield required for retention and retrieval, but contributions of these subregions to perceptual processes is understudied. The current study examined the nature and extent of a double dissociation between the dentate gyrus (DG) to discrimination processes and CA1 subfield to retention/retrieval by testing two unique individuals with bilateral damage to the DG (case BL) and CA1 (case BR). We tested BL and BR on a wide range of standardized neuropsychological tests to assess information encoding and retention/retrieval and co-opted many measures to assess perceptual discrimination. Compared to normative data, BL exhibited performance below expectations on most measures requiring perceptual discrimination and on measures of encoding but demonstrated intact retention. Conversely, BR showed no difficulties with perceptual discrimination or verbal encoding but exhibited poor verbal retention, as well as poor encoding and retention of spatial/integrative tasks (e.g., object in a location). These results indicate that, despite its prominent role in memory, the DG is necessary for perceptual discrimination and encoding, whereas CA1 is necessary for retention/retrieval and encoding of spatial information. The pattern of results highlights the critical nature of individual case studies in the nuanced understanding of HPC subfield contributions to different memory processes, as well as the utility of repurposing neuropsychological measures to capture individual differences.
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Affiliation(s)
- Krista A Mitchnick
- Department of Psychology, York University, Toronto, ON, Canada; Rotman Research Institute at Baycrest Hospital, Toronto, ON, Canada.
| | - Sabrina Labardo
- Department of Psychology, York University, Toronto, ON, Canada.
| | - R Shayna Rosenbaum
- Department of Psychology, York University, Toronto, ON, Canada; Rotman Research Institute at Baycrest Hospital, Toronto, ON, Canada; Centre for Integrative and Applied Neuroscience, York University, Toronto, ON, Canada.
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5
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Huang LW, Torelli F, Chen HL, Bartos M. Context and space coding in mossy cell population activity. Cell Rep 2024; 43:114386. [PMID: 38909362 DOI: 10.1016/j.celrep.2024.114386] [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: 09/11/2023] [Revised: 05/07/2024] [Accepted: 06/05/2024] [Indexed: 06/25/2024] Open
Abstract
The dentate gyrus plays a key role in the discrimination of memories by segregating and storing similar episodes. Whether hilar mossy cells, which constitute a major excitatory principal cell type in the mammalian hippocampus, contribute to this decorrelation function has remained largely unclear. Using two-photon calcium imaging of head-fixed mice performing a spatial virtual reality task, we show that mossy cell populations robustly discriminate between familiar and novel environments. The degree of discrimination depends on the extent of visual cue differences between contexts. A context decoder revealed that successful environmental classification is explained mainly by activity difference scores of mossy cells. By decoding mouse position, we reveal that in addition to place cells, the coordinated activity among active mossy cells markedly contributes to the encoding of space. Thus, by decorrelating context information according to the degree of environmental differences, mossy cell populations support pattern separation processes within the dentate gyrus.
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Affiliation(s)
- Li-Wen Huang
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104 Freiburg, Germany
| | - Federico Torelli
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104 Freiburg, Germany; University of Freiburg, Faculty of Biology, 79104 Freiburg, Germany
| | - Hung-Ling Chen
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104 Freiburg, Germany; BrainLinks-BrainTools, University of Freiburg, 79104 Freiburg, Germany.
| | - Marlene Bartos
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104 Freiburg, Germany.
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6
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Gandit B, Posani L, Zhang CL, Saha S, Ortiz C, Allegra M, Schmidt-Hieber C. Transformation of spatial representations along hippocampal circuits. iScience 2024; 27:110361. [PMID: 39071886 PMCID: PMC11277690 DOI: 10.1016/j.isci.2024.110361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 03/01/2024] [Accepted: 06/21/2024] [Indexed: 07/30/2024] Open
Abstract
The hippocampus is thought to provide the brain with a cognitive map of the external world by processing various types of spatial information. To understand how essential spatial variables such as direction, position, and distance are transformed along its circuits to construct this global map, we perform single-photon widefield microendoscope calcium imaging in the dentate gyrus and CA3 of mice freely navigating along a narrow corridor. We find that spatial activity maps in the dentate gyrus, but not in CA3, are correlated after aligning them to the running directions, suggesting that they represent the distance traveled along the track in egocentric coordinates. Together with population activity decoding, our data suggest that while spatial representations in the dentate gyrus and CA3 are anchored in both egocentric and allocentric coordinates, egocentric distance coding is more prevalent in the dentate gyrus than in CA3, providing insights into the assembly of the cognitive map.
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Affiliation(s)
- Bérénice Gandit
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015 Paris, France
- Sorbonne Université, Collège Doctoral, F-75005 Paris, France
| | - Lorenzo Posani
- Center for Theoretical Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA
| | - Chun-Lei Zhang
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015 Paris, France
| | - Soham Saha
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015 Paris, France
| | - Cantin Ortiz
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015 Paris, France
- Sorbonne Université, Collège Doctoral, F-75005 Paris, France
| | - Manuela Allegra
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015 Paris, France
| | - Christoph Schmidt-Hieber
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015 Paris, France
- Institute for Physiology I, Jena University Hospital, 07743 Jena, Germany
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7
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Miranda M, Silva A, Morici JF, Coletti MA, Belluscio M, Bekinschtein P. Retrieval of contextual memory can be predicted by CA3 remapping and is differentially influenced by NMDAR activity in rat hippocampus subregions. PLoS Biol 2024; 22:e3002706. [PMID: 38950066 PMCID: PMC11244845 DOI: 10.1371/journal.pbio.3002706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 07/12/2024] [Accepted: 06/12/2024] [Indexed: 07/03/2024] Open
Abstract
Episodic memory is essential to navigate in a changing environment by recalling past events, creating new memories, and updating stored information from experience. Although the mechanisms for acquisition and consolidation have been profoundly studied, much less is known about memory retrieval. Hippocampal spatial representations are key for retrieval of contextually guided episodic memories. Indeed, hippocampal place cells exhibit stable location-specific activity which is thought to support contextual memory, but can also undergo remapping in response to environmental changes. It is unclear if remapping is directly related to the expression of different episodic memories. Here, using an incidental memory recognition task in rats, we showed that retrieval of a contextually guided memory is reflected by the levels of CA3 remapping, demonstrating a clear link between external cues, hippocampal remapping, and episodic memory retrieval that guides behavior. Furthermore, we describe NMDARs as key players in regulating the balance between retrieval and memory differentiation processes by controlling the reactivation of specific memory traces. While an increase in CA3 NMDAR activity boosts memory retrieval, dentate gyrus NMDAR activity enhances memory differentiation. Our results contribute to understanding how the hippocampal circuit sustains a flexible balance between memory formation and retrieval depending on the environmental cues and the internal representations of the individual. They also provide new insights into the molecular mechanisms underlying the contributions of hippocampal subregions to generate this balance.
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Affiliation(s)
- Magdalena Miranda
- Laboratorio de Memoria y Cognición Molecular, Instituto de Neurociencia Cognitiva y Traslacional, CONICET-Fundación INECO-Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Azul Silva
- Laboratorio Bases neuronales del comportamiento, Departamento de Ciencias Fisiológicas, Facultad de Ciencias Médicas, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
- CONICET—Universidad de Buenos Aires, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay), Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Juan Facundo Morici
- Laboratorio de Memoria y Cognición Molecular, Instituto de Neurociencia Cognitiva y Traslacional, CONICET-Fundación INECO-Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Marcos Antonio Coletti
- Laboratorio Bases neuronales del comportamiento, Departamento de Ciencias Fisiológicas, Facultad de Ciencias Médicas, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
- CONICET—Universidad de Buenos Aires, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay), Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Mariano Belluscio
- Laboratorio Bases neuronales del comportamiento, Departamento de Ciencias Fisiológicas, Facultad de Ciencias Médicas, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
- CONICET—Universidad de Buenos Aires, Instituto de Fisiología y Biofísica Bernardo Houssay (IFIBIO Houssay), Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Pedro Bekinschtein
- Laboratorio de Memoria y Cognición Molecular, Instituto de Neurociencia Cognitiva y Traslacional, CONICET-Fundación INECO-Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
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8
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Lehtonen SM, Puumalainen V, Nokia MS, Lensu S. Effects of unilateral hippocampal surgical procedures needed for calcium imaging on mouse behavior and adult hippocampal neurogenesis. Behav Brain Res 2024; 468:115042. [PMID: 38723676 DOI: 10.1016/j.bbr.2024.115042] [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: 11/13/2023] [Revised: 04/17/2024] [Accepted: 05/03/2024] [Indexed: 05/16/2024]
Abstract
Hippocampus is essential for episodic memory formation, lesion studies demonstrating its role especially in processing spatial and temporal information. Further, adult hippocampal neurogenesis (AHN) in the dentate gyrus (DG) has also been linked to learning. To study hippocampal neuronal activity during events like learning, in vivo calcium imaging has become increasingly popular. It relies on the use of adeno-associated viral (AAV) vectors, which seem to lead to a decrease in AHN when applied on the DG. More notably, imaging requires the implantation of a relatively large lens into the tissue. Here, we examined how injection of an AAV vector and implantation of a 1-mm-diameter lens into the dorsal DG routinely used to image calcium activity impact the behavior of adult male C57BL/6 mice. To this aim, we conducted open-field, object-recognition and object-location tasks at baseline, after AAV vector injection, and after lens implantation. Finally, we determined AHN from hippocampal slices using a doublecortin-antibody. According to our results, the operations needed for in vivo imaging of the dorsal DG did not have adverse effects on behavior, although we noticed a decrease in AHN ipsilaterally to the operations. Thus, our results suggest that in vivo imaging can be safely used to, for example, correlate patterns of calcium activity with learned behavior. One should still keep in mind that the defects on the operated side might be functionally compensated by the (hippocampus in the) contralateral hemisphere.
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Affiliation(s)
- Suvi-Maaria Lehtonen
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Finland.
| | - Veera Puumalainen
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Finland
| | - Miriam S Nokia
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Finland
| | - Sanna Lensu
- Department of Psychology and Centre for Interdisciplinary Brain Research, University of Jyvaskyla, Finland
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9
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Boyle LM, Posani L, Irfan S, Siegelbaum SA, Fusi S. Tuned geometries of hippocampal representations meet the computational demands of social memory. Neuron 2024; 112:1358-1371.e9. [PMID: 38382521 PMCID: PMC11186585 DOI: 10.1016/j.neuron.2024.01.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 11/03/2023] [Accepted: 01/19/2024] [Indexed: 02/23/2024]
Abstract
Social memory consists of two processes: the detection of familiar compared with novel conspecifics and the detailed recollection of past social episodes. We investigated the neural bases for these processes using calcium imaging of dorsal CA2 hippocampal pyramidal neurons, known to be important for social memory, during social/spatial encounters with novel conspecifics and familiar littermates. Whereas novel individuals were represented in a low-dimensional geometry that allows for generalization of social identity across different spatial locations and of location across different identities, littermates were represented in a higher-dimensional geometry that supports high-capacity memory storage. Moreover, familiarity was represented in an abstract format, independent of individual identity. The degree to which familiarity increased the dimensionality of CA2 representations for individual mice predicted their performance in a social novelty recognition memory test. Thus, by tuning the geometry of structured neural activity, CA2 is able to meet the demands of distinct social memory processes.
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Affiliation(s)
- Lara M Boyle
- Department of Neuroscience, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY 10027, USA
| | - Lorenzo Posani
- Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | | | - Steven A Siegelbaum
- Department of Neuroscience, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Department of Pharmacology, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10027, USA.
| | - Stefano Fusi
- Department of Neuroscience, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY 10027, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10027, USA.
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10
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Hainmueller T, Cazala A, Huang LW, Bartos M. Subfield-specific interneuron circuits govern the hippocampal response to novelty in male mice. Nat Commun 2024; 15:714. [PMID: 38267409 PMCID: PMC10808551 DOI: 10.1038/s41467-024-44882-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 01/04/2024] [Indexed: 01/26/2024] Open
Abstract
The hippocampus is the brain's center for episodic memories. Its subregions, the dentate gyrus and CA1-3, are differentially involved in memory encoding and recall. Hippocampal principal cells represent episodic features like movement, space, and context, but less is known about GABAergic interneurons. Here, we performed two-photon calcium imaging of parvalbumin- and somatostatin-expressing interneurons in the dentate gyrus and CA1-3 of male mice exploring virtual environments. Parvalbumin-interneurons increased activity with running-speed and reduced it in novel environments. Somatostatin-interneurons in CA1-3 behaved similar to parvalbumin-expressing cells, but their dentate gyrus counterparts increased activity during rest and in novel environments. Congruently, chemogenetic silencing of dentate parvalbumin-interneurons had prominent effects in familiar contexts, while silencing somatostatin-expressing cells increased similarity of granule cell representations between novel and familiar environments. Our data indicate unique roles for parvalbumin- and somatostatin-positive interneurons in the dentate gyrus that are distinct from those in CA1-3 and may support routing of novel information.
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Affiliation(s)
- Thomas Hainmueller
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104, Freiburg, Germany.
- NYU Neuroscience Institute, 435 East 30th Street, New York, NY, 10016, USA.
- Department of Psychiatry, New York University Langone Medical Center, New York, NY, 10016, USA.
| | - Aurore Cazala
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104, Freiburg, Germany
| | - Li-Wen Huang
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104, Freiburg, Germany
| | - Marlene Bartos
- Institute for Physiology I, University of Freiburg, Medical Faculty, 79104, Freiburg, Germany.
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11
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Robert V, O'Neil K, Rashid SK, Johnson CD, De La Torre RG, Zemelman BV, Clopath C, Basu J. Entorhinal cortex glutamatergic and GABAergic projections bidirectionally control discrimination and generalization of hippocampal representations. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.566107. [PMID: 37986793 PMCID: PMC10659280 DOI: 10.1101/2023.11.08.566107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Discrimination and generalization are crucial brain-wide functions for memory and object recognition that utilize pattern separation and completion computations. Circuit mechanisms supporting these operations remain enigmatic. We show lateral entorhinal cortex glutamatergic (LEC GLU ) and GABAergic (LEC GABA ) projections are essential for object recognition memory. Silencing LEC GLU during in vivo two-photon imaging increased the population of active CA3 pyramidal cells but decreased activity rates, suggesting a sparse coding function through local inhibition. Silencing LEC GLU also decreased place cell remapping between different environments validating this circuit drives pattern separation and context discrimination. Optogenetic circuit mapping confirmed that LEC GLU drives dominant feedforward inhibition to prevent CA3 somatic and dendritic spikes. However, conjunctively active LEC GABA suppresses this local inhibition to disinhibit CA3 pyramidal neuron soma and selectively boost integrative output of LEC and CA3 recurrent network. LEC GABA thus promotes pattern completion and context generalization. Indeed, without this disinhibitory input, CA3 place maps show decreased similarity between contexts. Our findings provide circuit mechanisms whereby long-range glutamatergic and GABAergic cortico-hippocampal inputs bidirectionally modulate pattern separation and completion, providing neuronal representations with a dynamic range for context discrimination and generalization.
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12
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Borzello M, Ramirez S, Treves A, Lee I, Scharfman H, Stark C, Knierim JJ, Rangel LM. Assessments of dentate gyrus function: discoveries and debates. Nat Rev Neurosci 2023; 24:502-517. [PMID: 37316588 PMCID: PMC10529488 DOI: 10.1038/s41583-023-00710-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2023] [Indexed: 06/16/2023]
Abstract
There has been considerable speculation regarding the function of the dentate gyrus (DG) - a subregion of the mammalian hippocampus - in learning and memory. In this Perspective article, we compare leading theories of DG function. We note that these theories all critically rely on the generation of distinct patterns of activity in the region to signal differences between experiences and to reduce interference between memories. However, these theories are divided by the roles they attribute to the DG during learning and recall and by the contributions they ascribe to specific inputs or cell types within the DG. These differences influence the information that the DG is thought to impart to downstream structures. We work towards a holistic view of the role of DG in learning and memory by first developing three critical questions to foster a dialogue between the leading theories. We then evaluate the extent to which previous studies address our questions, highlight remaining areas of conflict, and suggest future experiments to bridge these theories.
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Affiliation(s)
- Mia Borzello
- Department of Cognitive Science, University of California, San Diego, La Jolla, CA, USA
| | - Steve Ramirez
- Department of Psychological and Brain Sciences, Boston University, Boston, MA, USA
| | | | - Inah Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, South Korea
| | - Helen Scharfman
- Departments of Child and Adolescent Psychiatry, Neuroscience and Physiology and Psychiatry and the Neuroscience Institute, New York University Langone Health, New York, NY, USA
- The Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, USA
| | - Craig Stark
- Department of Neurobiology and Behaviour, University of California, Irvine, Irvine, CA, USA
| | - James J Knierim
- Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Lara M Rangel
- Department of Cognitive Science, University of California, San Diego, La Jolla, CA, USA.
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13
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Kim SH, GoodSmith D, Temme SJ, Moriya F, Ming GL, Christian KM, Song H, Knierim JJ. Global remapping in granule cells and mossy cells of the mouse dentate gyrus. Cell Rep 2023; 42:112334. [PMID: 37043350 PMCID: PMC10564968 DOI: 10.1016/j.celrep.2023.112334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 02/02/2023] [Accepted: 03/17/2023] [Indexed: 04/13/2023] Open
Abstract
Hippocampal place cells exhibit spatially modulated firing, or place fields, which can remap to encode changes in the environment or other variables. Unique among hippocampal subregions, the dentate gyrus (DG) has two excitatory populations of place cells, granule cells and mossy cells, which are among the least and most active spatially modulated cells in the hippocampus, respectively. Previous studies of remapping in the DG have drawn different conclusions about whether granule cells exhibit global remapping and contribute to the encoding of context specificity. By recording granule cells and mossy cells as mice foraged in different environments, we found that by most measures, both granule cells and mossy cells remapped robustly but through different mechanisms that are consistent with firing properties of each cell type. Our results resolve the ambiguity surrounding remapping in the DG and suggest that most spatially modulated granule cells contribute to orthogonal representations of distinct spatial contexts.
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Affiliation(s)
- Sang Hoon Kim
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Douglas GoodSmith
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neurobiology and Neuroscience Institute, University of Chicago, Chicago, IL 60637, USA
| | - Stephanie J Temme
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Fumika Moriya
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Guo-Li Ming
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kimberly M Christian
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Hongjun Song
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; The Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - James J Knierim
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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14
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Rukundo P, Feng T, Pham V, Pieraut S. Moderate effect of early-life experience on dentate gyrus function. Mol Brain 2022; 15:92. [PMID: 36411441 PMCID: PMC9677655 DOI: 10.1186/s13041-022-00980-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/06/2022] [Indexed: 11/22/2022] Open
Abstract
The development, maturation, and plasticity of neural circuits are strongly influenced by experience and the interaction of an individual with their environment can have a long-lasting effect on cognitive function. Using an enriched environment (EE) paradigm, we have recently demonstrated that enhancing social, physical, and sensory activity during the pre-weaning time in mice led to an increase of inhibitory and excitatory synapses in the dentate gyrus (DG) of the hippocampus. The structural plasticity induced by experience may affect information processing in the circuit. The DG performs pattern separation, a computation that enables the encoding of very similar and overlapping inputs into dissimilar outputs. In the presented study, we have tested the hypothesis that an EE in juvenile mice will affect DG's functions that are relevant for pattern separation: the decorrelation of the inputs from the entorhinal cortex (EC) and the recruitment of the principal excitatory granule cell (GC) during behavior. First, using a novel slice electrophysiology protocol, we found that the transformation of the incoming signal from the EC afferents by individual GC is moderately affected by EE. We further show that EE does not affect behaviorally induced recruitment of principal excitatory GC. Lastly, using the novel object recognition task, a hippocampus-dependent memory test, we show that the ontogeny of this discrimination task was similar among the EE mice and the controls. Taken together, our work demonstrates that pre-weaning enrichment moderately affects DG function.
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Affiliation(s)
- Pacifique Rukundo
- grid.266818.30000 0004 1936 914XDepartment of Biology, University of Nevada, Reno, NV 89557 USA
| | - Ting Feng
- grid.266818.30000 0004 1936 914XDepartment of Biology, University of Nevada, Reno, NV 89557 USA
| | - Vincent Pham
- grid.266818.30000 0004 1936 914XDepartment of Biology, University of Nevada, Reno, NV 89557 USA
| | - Simon Pieraut
- grid.266818.30000 0004 1936 914XDepartment of Biology, University of Nevada, Reno, NV 89557 USA
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15
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Cholvin T, Bartos M. Hemisphere-specific spatial representation by hippocampal granule cells. Nat Commun 2022; 13:6227. [PMID: 36266288 PMCID: PMC9585038 DOI: 10.1038/s41467-022-34039-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 10/11/2022] [Indexed: 12/24/2022] Open
Abstract
The dentate gyrus (DG) output plays a key role in the emergence of spatial and contextual map representation within the hippocampus during learning. Differences in neuronal network activity have been observed between left and right CA1-3 areas, implying lateralization in spatial coding properties. Whether bilateral differences of DG granule cell (GC) assemblies encoding spatial and contextual information exist remains largely unexplored. Here, we employed two-photon calcium imaging of the left or the right DG to record the activity of GC populations over five consecutive days in head-fixed mice navigating through familiar and novel virtual environments. Imaging revealed similar mean GC activity on both sides. However, spatial tuning, context-selectivity and run-to-run place field reliability was markedly higher for DG place cells in the left than the right hemisphere. Moreover, the proportion of GCs reconfiguring their place fields between contexts was greater in the left DG. Thus, our data suggest that contextual information is differentially processed by GC populations depending on the hemisphere, with higher context discrimination in the left but a bias towards generalization in the right DG.
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Affiliation(s)
- Thibault Cholvin
- grid.5963.9Institute for Physiology I, University of Freiburg, Medical Faculty, 79104 Freiburg, Germany
| | - Marlene Bartos
- grid.5963.9Institute for Physiology I, University of Freiburg, Medical Faculty, 79104 Freiburg, Germany
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16
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Zorzo C, Arias JL, Méndez M. The removal and addition of cues does not impair spatial retrieval and leads to a different metabolic activity of the limbic network in female rats. Brain Res Bull 2022; 190:22-31. [PMID: 36126874 DOI: 10.1016/j.brainresbull.2022.09.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 08/07/2022] [Accepted: 09/16/2022] [Indexed: 11/02/2022]
Abstract
The retrieval of spatial memories does not always occur in an environment with the same stimuli configuration where the memory was first formed. However, re-exposure to a partial portion of the previously encountered cues can elicit memory successfully. Navigation with contextual changes has received little attention, especially in females. Thus, we aimed to assess memory retrieval using the Morris Water Maze spatial reference protocol in female adult Wistar rats. Rats were trained with five allocentric cues, and retrieval was explored one week later either with the same cues, or with four removed, or with three added cues. We studied the underlying brain oxidative metabolism of the hippocampus, prefrontal, parietal, retrosplenial, entorhinal, and perirhinal cortices through cytochrome c oxidase (CCO) histochemistry. Neither cue removal nor cue addition impaired retrieval performance. Retrieval with a degraded subset of cues led to increased prefrontal, hippocampal, retrosplenial, parietal, and perirhinal CCO activity. Retrieval with extra cues led to an enhancement of CCO activity in the hippocampus and retrosplenial cortex. Different patterns of network intercorrelations were found. The cue-removal group presented a closed reciprocal network, while the group with extra cues had separate parallel networks. Both groups showed a simpler network than the group with no cue modifications. Future research is needed to delve into behavioral and brain-related functions of spatial memory processes under modified environmental conditions.
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Affiliation(s)
- Candela Zorzo
- Department of Psychology, University of Oviedo, Plaza Feijoo, s/n, E-33003 Oviedo, Spain; Instituto de Neurociencias del Principado de Asturias (INEUROPA), E-33003 Oviedo, Spain; Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33006 Oviedo, Spain.
| | - Jorge L Arias
- Department of Psychology, University of Oviedo, Plaza Feijoo, s/n, E-33003 Oviedo, Spain; Instituto de Neurociencias del Principado de Asturias (INEUROPA), E-33003 Oviedo, Spain; Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33006 Oviedo, Spain.
| | - Marta Méndez
- Department of Psychology, University of Oviedo, Plaza Feijoo, s/n, E-33003 Oviedo, Spain; Instituto de Neurociencias del Principado de Asturias (INEUROPA), E-33003 Oviedo, Spain; Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33006 Oviedo, Spain.
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17
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Abstract
Astrocytic calcium dynamics has been implicated in the encoding of sensory information1-5, and modulation of calcium in astrocytes has been shown to affect behaviour6-10. However, longitudinal investigation of the real-time calcium activity of astrocytes in the hippocampus of awake mice is lacking. Here we used two-photon microscopy to chronically image CA1 astrocytes as mice ran in familiar or new virtual environments to obtain water rewards. We found that astrocytes exhibit persistent ramping activity towards the reward location in a familiar environment, but not in a new one. Shifting the reward location within a familiar environment also resulted in diminished ramping. After additional training, as the mice became familiar with the new context or new reward location, the ramping was re-established. Using linear decoders, we could predict the location of the mouse in a familiar environment from astrocyte activity alone. We could not do the same in a new environment, suggesting that the spatial modulation of astrocytic activity is experience dependent. Our results indicate that astrocytes can encode the expected reward location in spatial contexts, thereby extending their known computational abilities and their role in cognitive functions.
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18
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Gómez-Ocádiz R, Trippa M, Zhang CL, Posani L, Cocco S, Monasson R, Schmidt-Hieber C. A synaptic signal for novelty processing in the hippocampus. Nat Commun 2022; 13:4122. [PMID: 35840595 PMCID: PMC9287442 DOI: 10.1038/s41467-022-31775-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 07/04/2022] [Indexed: 12/25/2022] Open
Abstract
Episodic memory formation and recall are complementary processes that rely on opposing neuronal computations in the hippocampus. How this conflict is resolved in hippocampal circuits is unclear. To address this question, we obtained in vivo whole-cell patch-clamp recordings from dentate gyrus granule cells in head-fixed mice trained to explore and distinguish between familiar and novel virtual environments. We find that granule cells consistently show a small transient depolarisation upon transition to a novel environment. This synaptic novelty signal is sensitive to local application of atropine, indicating that it depends on metabotropic acetylcholine receptors. A computational model suggests that the synaptic response to novelty may bias granule cell population activity, which can drive downstream attractor networks to a new state, favouring the switch from recall to new memory formation when faced with novelty. Such a novelty-driven switch may enable flexible encoding of new memories while preserving stable retrieval of familiar ones. Memory formation and recall are complementary processes within the hippocampus. Here the authors demonstrate a synaptic signal of novelty in the hippocampus and provide a computational framework for how such a novelty-driven switch may enable flexible encoding of new memories while preserving stable retrieval of familiar ones.
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Affiliation(s)
- Ruy Gómez-Ocádiz
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015, Paris, France.,Sorbonne Université, Collège Doctoral, F-75005, Paris, France.,Department of Neuroscience, Karolinska Institutet, 17177, Stockholm, Sweden
| | - Massimiliano Trippa
- Laboratory of Physics of the École Normale Supérieure, PSL Research and CNRS UMR 8023, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Chun-Lei Zhang
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015, Paris, France
| | - Lorenzo Posani
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015, Paris, France.,Center for Theoretical Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA
| | - Simona Cocco
- Laboratory of Physics of the École Normale Supérieure, PSL Research and CNRS UMR 8023, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Rémi Monasson
- Laboratory of Physics of the École Normale Supérieure, PSL Research and CNRS UMR 8023, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Christoph Schmidt-Hieber
- Institut Pasteur, Université Paris Cité, Neural Circuits for Spatial Navigation and Memory, Department of Neuroscience, F-75015, Paris, France.
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19
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Mitchnick KA, Ahmad Z, Mitchnick SD, Ryan JD, Rosenbaum RS, Freud E. Damage to the human dentate gyrus impairs the perceptual discrimination of complex, novel objects. Neuropsychologia 2022; 172:108238. [PMID: 35513066 DOI: 10.1016/j.neuropsychologia.2022.108238] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 01/25/2022] [Accepted: 04/07/2022] [Indexed: 11/19/2022]
Abstract
The hippocampus (HPC), and the dentate gyrus (DG) subregion in particular, is purported to be a pattern separator, orthogonally representing similar information so that distinct memories may be formed. The HPC may also be involved in complex perceptual discrimination. It is unclear if this role is limited to spatial/scene stimuli or extends to the discrimination of objects. Also unclear is whether the DG itself contributes to pattern separation beyond memory. BL, an individual with bilateral DG lesions, was previously shown to have poor discrimination of similar, everyday objects in memory. Here, we demonstrate that BL's deficit extends to complex perceptual discrimination of novel objects. Specifically, BL was presented with closely matched possible and impossible objects, which give rise to fundamentally different 3D perceptual representations despite being visually similar. BL performed significantly worse than controls when asked to select an odd object (e.g., impossible) amongst three identical counterpart objects (e.g., possible) presented at different rotations. His deficit was also evident in an atypical eye fixation pattern during this task. In contrast, BL's performance was indistinguishable from that of controls on other tasks involving the same objects, indicating that he could visually differentiate the object pairs, that he perceived the objects holistically in 3D, and that he has only a mild weakness in categorizing object possibility. Furthermore, his performance on standardized neuropsychological measures indicated intact mental rotation, visual-spatial attention, and working memory (visual and auditory). Collectively, these results provide evidence that the DG is necessary for complex perceptual discrimination of novel objects, indicating that the DG might function as a generic pattern separator of a wide range of stimuli within high-level perception, and that its role is not limited to memory.
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Affiliation(s)
- K A Mitchnick
- York University, Toronto, Canada; Rotman Research Institute at Baycrest Hospital, Toronto, Canada.
| | - Z Ahmad
- York University, Toronto, Canada
| | | | - J D Ryan
- Rotman Research Institute at Baycrest Hospital, Toronto, Canada
| | - R S Rosenbaum
- York University, Toronto, Canada; Rotman Research Institute at Baycrest Hospital, Toronto, Canada.
| | - E Freud
- York University, Toronto, Canada.
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20
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Hippocampal place codes are gated by behavioral engagement. Nat Neurosci 2022; 25:561-566. [PMID: 35449355 PMCID: PMC9076532 DOI: 10.1038/s41593-022-01050-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 03/14/2022] [Indexed: 11/27/2022]
Abstract
As animals explore an environment, the hippocampus is thought to automatically form and maintain a place code by combining sensory and self-motion signals. Instead, we observed an extensive degradation of the place code when mice voluntarily disengaged from a virtual navigation task, remarkably even as they continued to traverse the identical environment. Internal states, therefore, can strongly gate spatial maps and reorganize hippocampal activity even without sensory and self-motion changes. The authors found that the expression of spatial maps in the hippocampus is modulated by the internal state of an animal. Thus, the brain’s code for spatial positions within an environment can transform even without changes to the external world.
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21
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GoodSmith D, Kim SH, Puliyadi V, Ming GL, Song H, Knierim JJ, Christian KM. Flexible encoding of objects and space in single cells of the dentate gyrus. Curr Biol 2022; 32:1088-1101.e5. [PMID: 35108522 PMCID: PMC8930604 DOI: 10.1016/j.cub.2022.01.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 11/12/2021] [Accepted: 01/10/2022] [Indexed: 01/05/2023]
Abstract
The hippocampus is involved in the formation of memories that require associations among stimuli to construct representations of space and the items and events within that space. Neurons in the dentate gyrus (DG), an initial input region of the hippocampus, have robust spatial tuning, but it is unclear how nonspatial information may be integrated with spatial activity in this region. We recorded from the DG of 21 adult mice as they foraged for food in an environment that contained discrete objects. We found DG cells with multiple firing fields at a fixed distance and direction from objects (landmark vector cells) and cells that exhibited localized changes in spatial firing when objects in the environment were manipulated. By classifying recorded DG cells into putative dentate granule cells and mossy cells, we examined how the addition or displacement of objects affected the spatial firing of these DG cell types. Object-related activity was detected in a significant proportion of mossy cells. Although few granule cells with responses to object manipulations were recorded, likely because of the sparse nature of granule cell firing, there was generally no significant difference in the proportion of granule cells and mossy cells with object responses. When mice explored a second environment with the same objects, DG spatial maps completely reorganized, and a different subset of cells responded to object manipulations. Together, these data reveal the capacity of DG cells to detect small changes in the environment while preserving a stable spatial representation of the overall context.
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Affiliation(s)
- Douglas GoodSmith
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA; Department of Neurobiology and Neuroscience Institute, University of Chicago, 5801 S Ellis Avenue, Chicago, IL 60637, USA
| | - Sang Hoon Kim
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA
| | - Vyash Puliyadi
- Department of Psychological and Brain Sciences, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
| | - Guo-Li Ming
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA
| | - Hongjun Song
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; The Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA.
| | - James J Knierim
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA.
| | - Kimberly M Christian
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA.
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22
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Eom K, Lee HR, Hyun JH, An H, Lee YS, Ho WK, Lee SH. Gradual decorrelation of CA3 ensembles associated with contextual discrimination learning is impaired by Kv1.2 insufficiency. Hippocampus 2022; 32:193-216. [PMID: 34964210 DOI: 10.1002/hipo.23400] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 11/30/2021] [Accepted: 12/12/2021] [Indexed: 12/13/2022]
Abstract
The associative network of hippocampal CA3 is thought to contribute to rapid formation of contextual memory from one-trial learning, but the network mechanisms underlying decorrelation of neuronal ensembles in CA3 is largely unknown. Kv1.2 expressions in rodent CA3 pyramidal cells (CA3-PCs) are polarized to distal apical dendrites, and its downregulation specifically enhances dendritic responses to perforant pathway (PP) synaptic inputs. We found that haploinsufficiency of Kv1.2 (Kcna2+/-) in CA3-PCs, but not Kv1.1 (Kcna1+/-), lowers the threshold for long-term potentiation (LTP) at PP-CA3 synapses, and that the Kcna2+/- mice are normal in discrimination of distinct contexts but impaired in discrimination of similar but slightly distinct contexts. We further examined the neuronal ensembles in CA3 and dentate gyrus (DG), which represent the two similar contexts using in situ hybridization of immediate early genes, Homer1a and Arc. The size and overlap of CA3 ensembles activated by the first visit to the similar contexts were not different between wild type and Kcna2+/- mice, but these ensemble parameters diverged over training days between genotypes, suggesting that abnormal plastic changes at PP-CA3 synapses of Kcna2+/- mice is responsible for the impaired pattern separation. Unlike CA3, DG ensembles were not different between two genotype mice. The DG ensembles were already separated on the first day, and their overlap did not further evolve. Eventually, the Kcna2+/- mice exhibited larger CA3 ensemble size and overlap upon retrieval of two contexts, compared to wild type or Kcna1+/- mice. These results suggest that sparse LTP at PP-CA3 synapse probably supervised by mossy fiber inputs is essential for gradual decorrelation of CA3 ensembles.
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Affiliation(s)
- Kisang Eom
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Hyoung Ro Lee
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Jung Ho Hyun
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Hyunhoe An
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Brain and Cognitive Science, Seoul National University College of Natural Sciences, Seoul, Republic of Korea
| | - Yong-Seok Lee
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Won-Kyung Ho
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Brain and Cognitive Science, Seoul National University College of Natural Sciences, Seoul, Republic of Korea
| | - Suk-Ho Lee
- Cell Physiology Laboratory, Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Brain and Cognitive Science, Seoul National University College of Natural Sciences, Seoul, Republic of Korea
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23
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Twarkowksi H, Steininger V, Kim MJ, Sahay A. A dentate gyrus- CA3 inhibitory circuit promotes evolution of hippocampal-cortical ensembles during memory consolidation. eLife 2022; 11:70586. [PMID: 35191834 PMCID: PMC8903830 DOI: 10.7554/elife.70586] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 02/21/2022] [Indexed: 11/13/2022] Open
Abstract
Memories encoded in the dentate gyrus (DG) - CA3 circuit of the hippocampus are routed from CA1 to anterior cingulate cortex (ACC) for consolidation. Although CA1 parvalbumin inhibitory neurons (PV INs) orchestrate hippocampal-cortical communication, we know less about CA3 PV INs or DG - CA3 principal neuron - IN circuit mechanisms that contribute to evolution of hippocampal-cortical ensembles during memory consolidation. Using viral genetics to selectively mimic and boost an endogenous learning-dependent circuit mechanism, DG cell recruitment of CA3 PV INs and feed-forward inhibition (FFI) in CA3, in combination with longitudinal in vivo calcium imaging, we demonstrate that FFI facilitates formation and maintenance of context-associated neuronal ensembles in CA1. Increasing FFI in DG - CA3 promoted context specificity of neuronal ensembles in ACC over time and enhanced long-term contextual fear memory. In vivo LFP recordings in mice with increased FFI in DG - CA3 identified enhanced CA1 sharp-wave ripple - ACC spindle coupling as a potential network mechanism facilitating memory consolidation. Our findings illuminate how FFI in DG - CA3 dictates evolution of ensemble properties in CA1 and ACC during memory consolidation and suggest a teacher-like function for hippocampal CA1 in stabilization and re-organization of cortical representations.
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Affiliation(s)
- Hannah Twarkowksi
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, United States
| | - Victor Steininger
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, United States
| | - Min Jae Kim
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, United States
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, United States
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24
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Motanis H, Khorasani LN, Giza CC, Harris NG. Peering into the Brain through the Retrosplenial Cortex to Assess Cognitive Function of the Injured Brain. Neurotrauma Rep 2021; 2:564-580. [PMID: 34901949 PMCID: PMC8655812 DOI: 10.1089/neur.2021.0044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The retrosplenial cortex (RSC) is a posterior cortical area that has been drawing increasing interest in recent years, with a growing number of studies studying its contribution to cognitive and sensory functions. From an anatomical perspective, it has been established that the RSC is extensively and often reciprocally connected with the hippocampus, neocortex, and many midbrain regions. Functionally, the RSC is an important hub of the default-mode network. This endowment, with vast anatomical and functional connections, positions the RSC to play an important role in episodic memory, spatial and contextual learning, sensory-cognitive activities, and multi-modal sensory information processing and integration. Additionally, RSC dysfunction has been reported in cases of cognitive decline, particularly in Alzheimer's disease and stroke. We review the literature to examine whether the RSC can act as a cortical marker of persistent cognitive dysfunction after traumatic brain injury (TBI). Because the RSC is easily accessible at the brain's surface using in vivo techniques, we argue that studying RSC network activity post-TBI can shed light into the mechanisms of less-accessible brain regions, such as the hippocampus. There is a fundamental gap in the TBI field about the microscale alterations occurring post-trauma, and by studying the RSC's neuronal activity at the cellular level we will be able to design better therapeutic tools. Understanding how neuronal activity and interactions produce normal and abnormal activity in the injured brain is crucial to understanding cognitive dysfunction. By using this approach, we expect to gain valuable insights to better understand brain disorders like TBI.
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Affiliation(s)
- Helen Motanis
- UCLA Brain Injury Research Center, Department of Neurosurgery, Geffen Medical School, UCLA Mattel Children's Hospital, University of California at Los Angeles, Los Angeles, California, USA
| | - Laila N. Khorasani
- UCLA Brain Injury Research Center, Department of Neurosurgery, Geffen Medical School, UCLA Mattel Children's Hospital, University of California at Los Angeles, Los Angeles, California, USA
| | - Christopher C. Giza
- UCLA Brain Injury Research Center, Department of Neurosurgery, Geffen Medical School, UCLA Mattel Children's Hospital, University of California at Los Angeles, Los Angeles, California, USA
- Department of Pediatrics, UCLA Mattel Children's Hospital, University of California at Los Angeles, Los Angeles, California, USA
| | - Neil G. Harris
- UCLA Brain Injury Research Center, Department of Neurosurgery, Geffen Medical School, UCLA Mattel Children's Hospital, University of California at Los Angeles, Los Angeles, California, USA
- Intellectual Development and Disabilities Research Center, UCLA Mattel Children's Hospital, University of California at Los Angeles, Los Angeles, California, USA
- *Address correspondence to: Neil G. Harris, PhD, Department of Neurosurgery, University of California at Los Angeles, Wasserman Building, 300 Stein Plaza, Room 551, Los Angeles, CA 90095, USA;
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Design, synthesis, and biological evaluation of carbamate derivatives of N-salicyloyl tryptamine as multifunctional agents for the treatment of Alzheimer's disease. Eur J Med Chem 2021; 229:114044. [PMID: 34923430 DOI: 10.1016/j.ejmech.2021.114044] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/04/2021] [Accepted: 12/04/2021] [Indexed: 02/07/2023]
Abstract
In this study, we designed, synthesized, and evaluated a series of carbamate derivatives of N-salicyloyl tryptamine as multifunctional therapeutic agents for the treatment of Alzheimer's disease (AD). After screening the acetylcholinesterase (AChE)/butyrylcholinesterase (BChE) inhibitory activities, target compound 1g stood out as a mixed type reversible dual inhibitor of AChE and BChE. In addition, molecular docking studies were conducted to explore the actions on AChE and BChE. The results showed that 1g could decrease the level of pro-inflammatory cytokines NO, iNOS, IL-6, TNF-α, and ROS, increase the level of anti-inflammatory cytokines IL-4, and inhibit the aggregation of Aβ1-42. Moreover, the administration of 1g suppressed the activity of AChE in the brain. In a word, the compound 1g is effective for improving learning and memory behavior, blood-brain barrier permeation, pharmacokinetics, ChE inhibition, and anti-neuroinflammation. It may be considered as a promising multi-functional therapeutic agent for further investigation for the treatment of AD.
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Deficits in Behavioral and Neuronal Pattern Separation in Temporal Lobe Epilepsy. J Neurosci 2021; 41:9669-9686. [PMID: 34620720 PMCID: PMC8612476 DOI: 10.1523/jneurosci.2439-20.2021] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 09/09/2021] [Accepted: 09/21/2021] [Indexed: 11/21/2022] Open
Abstract
In temporal lobe epilepsy, the ability of the dentate gyrus to limit excitatory cortical input to the hippocampus breaks down, leading to seizures. The dentate gyrus is also thought to help discriminate between similar memories by performing pattern separation, but whether epilepsy leads to a breakdown in this neural computation, and thus to mnemonic discrimination impairments, remains unknown. Here we show that temporal lobe epilepsy is characterized by behavioral deficits in mnemonic discrimination tasks, in both humans (females and males) and mice (C57Bl6 males, systemic low-dose kainate model). Using a recently developed assay in brain slices of the same epileptic mice, we reveal a decreased ability of the dentate gyrus to perform certain forms of pattern separation. This is because of a subset of granule cells with abnormal bursting that can develop independently of early EEG abnormalities. Overall, our results linking physiology, computation, and cognition in the same mice advance our understanding of episodic memory mechanisms and their dysfunction in epilepsy.SIGNIFICANCE STATEMENT People with temporal lobe epilepsy (TLE) often have learning and memory impairments, sometimes occurring earlier than the first seizure, but those symptoms and their biological underpinnings are poorly understood. We focused on the dentate gyrus, a brain region that is critical to avoid confusion between similar memories and is anatomically disorganized in TLE. We show that both humans and mice with TLE experience confusion between similar situations. This impairment coincides with a failure of the dentate gyrus to disambiguate similar input signals because of pathologic bursting in a subset of neurons. Our work bridges seizure-oriented and memory-oriented views of the dentate gyrus function, suggests a mechanism for cognitive symptoms in TLE, and supports a long-standing hypothesis of episodic memory theories.
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Cholvin T, Hainmueller T, Bartos M. The hippocampus converts dynamic entorhinal inputs into stable spatial maps. Neuron 2021; 109:3135-3148.e7. [PMID: 34619088 PMCID: PMC8516433 DOI: 10.1016/j.neuron.2021.09.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 05/31/2021] [Accepted: 09/09/2021] [Indexed: 11/29/2022]
Abstract
The medial entorhinal cortex (MEC)-hippocampal network plays a key role in the processing, storage, and recall of spatial information. However, how the spatial code provided by MEC inputs relates to spatial representations generated by principal cell assemblies within hippocampal subfields remains enigmatic. To investigate this coding relationship, we employed two-photon calcium imaging in mice navigating through dissimilar virtual environments. Imaging large MEC bouton populations revealed spatially tuned activity patterns. MEC inputs drastically changed their preferred spatial field locations between environments, whereas hippocampal cells showed lower levels of place field reconfiguration. Decoding analysis indicated that higher place field reliability and larger context-dependent activity-rate differences allow low numbers of principal cells, particularly in the DG and CA1, to provide information about location and context more accurately and rapidly than MEC inputs. Thus, conversion of dynamic MEC inputs into stable spatial hippocampal maps may enable fast encoding and efficient recall of spatio-contextual information. MEC inputs to the DG, CA3, and CA1 show different spatial coding properties MEC inputs remap even more strongly than hippocampal principal cells Hippocampal principal cell activity is more reliable and stable than their MEC inputs Hippocampal principal cells allow improved spatial and contextual readout
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Affiliation(s)
- Thibault Cholvin
- Institute for Physiology I, University of Freiburg, Medical Faculty, Freiburg 79104, Germany
| | - Thomas Hainmueller
- NYU Neuroscience Institute, 435 East 30th Street, New York, NY 10016, USA
| | - Marlene Bartos
- Institute for Physiology I, University of Freiburg, Medical Faculty, Freiburg 79104, Germany.
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Dong C, Madar AD, Sheffield MEJ. Distinct place cell dynamics in CA1 and CA3 encode experience in new environments. Nat Commun 2021; 12:2977. [PMID: 34016996 PMCID: PMC8137926 DOI: 10.1038/s41467-021-23260-3] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 04/21/2021] [Indexed: 02/07/2023] Open
Abstract
When exploring new environments animals form spatial memories that are updated with experience and retrieved upon re-exposure to the same environment. The hippocampus is thought to support these memory processes, but how this is achieved by different subnetworks such as CA1 and CA3 remains unclear. To understand how hippocampal spatial representations emerge and evolve during familiarization, we performed 2-photon calcium imaging in mice running in new virtual environments and compared the trial-to-trial dynamics of place cells in CA1 and CA3 over days. We find that place fields in CA1 emerge rapidly but tend to shift backwards from trial-to-trial and remap upon re-exposure to the environment a day later. In contrast, place fields in CA3 emerge gradually but show more stable trial-to-trial and day-to-day dynamics. These results reflect different roles in CA1 and CA3 in spatial memory processing during familiarization to new environments and constrain the potential mechanisms that support them.
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MESH Headings
- Animals
- Behavior Observation Techniques
- Behavior, Animal/physiology
- CA1 Region, Hippocampal/cytology
- CA1 Region, Hippocampal/diagnostic imaging
- CA1 Region, Hippocampal/physiology
- CA3 Region, Hippocampal/cytology
- CA3 Region, Hippocampal/diagnostic imaging
- CA3 Region, Hippocampal/physiology
- Craniotomy
- Intravital Microscopy/instrumentation
- Intravital Microscopy/methods
- Male
- Mice
- Microscopy, Confocal/instrumentation
- Microscopy, Confocal/methods
- Models, Animal
- Optical Imaging/instrumentation
- Optical Imaging/methods
- Place Cells/physiology
- Space Perception/physiology
- Spatial Memory/physiology
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Affiliation(s)
- Can Dong
- Department of Neurobiology and Institute for Neuroscience, University of Chicago, Chicago, IL, USA
| | - Antoine D Madar
- Department of Neurobiology and Institute for Neuroscience, University of Chicago, Chicago, IL, USA
| | - Mark E J Sheffield
- Department of Neurobiology and Institute for Neuroscience, University of Chicago, Chicago, IL, USA.
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Abstract
Neural correlates of external variables provide potential internal codes that guide an animal’s behaviour. Notably, first-order features of neural activity, such as single-neuron firing rates, have been implicated in encoding information. However, the extent to which higher-order features, such as multi-neuron coactivity, play primary roles in encoding information or secondary roles in supporting single-neuron codes remains unclear. Here we show that millisecond-timescale coactivity amongst hippocampal CA1 neurons discriminates distinct millisecond-lived behavioural contingencies. This contingency discrimination was unrelated to the tuning of individual neurons but instead an emergent property of their coactivity. Contingency discriminating patterns were reactivated offline after learning and their reinstatement predicted trial-by-trial memory performance. Moreover, optogenetic suppression of inputs from the upstream CA3 region selectively during learning impaired coactivity-based contingency information in CA1 and subsequent dynamic memory retrieval. These findings identify coactivity as a primary feature of neural firing that discriminates distinct behaviourally-relevant variables and supports memory retrieval.
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