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Sutton NM, Gutiérrez-Guzmán BE, Dannenberg H, Ascoli GA. A Continuous Attractor Model with Realistic Neural and Synaptic Properties Quantitatively Reproduces Grid Cell Physiology. Int J Mol Sci 2024; 25:6059. [PMID: 38892248 PMCID: PMC11173171 DOI: 10.3390/ijms25116059] [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: 04/29/2024] [Revised: 05/25/2024] [Accepted: 05/26/2024] [Indexed: 06/21/2024] Open
Abstract
Computational simulations with data-driven physiological detail can foster a deeper understanding of the neural mechanisms involved in cognition. Here, we utilize the wealth of cellular properties from Hippocampome.org to study neural mechanisms of spatial coding with a spiking continuous attractor network model of medial entorhinal cortex circuit activity. The primary goal is to investigate if adding such realistic constraints could produce firing patterns similar to those measured in real neurons. Biological characteristics included in the work are excitability, connectivity, and synaptic signaling of neuron types defined primarily by their axonal and dendritic morphologies. We investigate the spiking dynamics in specific neuron types and the synaptic activities between groups of neurons. Modeling the rodent hippocampal formation keeps the simulations to a computationally reasonable scale while also anchoring the parameters and results to experimental measurements. Our model generates grid cell activity that well matches the spacing, size, and firing rates of grid fields recorded in live behaving animals from both published datasets and new experiments performed for this study. Our simulations also recreate different scales of those properties, e.g., small and large, as found along the dorsoventral axis of the medial entorhinal cortex. Computational exploration of neuronal and synaptic model parameters reveals that a broad range of neural properties produce grid fields in the simulation. These results demonstrate that the continuous attractor network model of grid cells is compatible with a spiking neural network implementation sourcing data-driven biophysical and anatomical parameters from Hippocampome.org. The software (version 1.0) is released as open source to enable broad community reuse and encourage novel applications.
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Affiliation(s)
- Nate M. Sutton
- Bioengineering Department, George Mason University, Fairfax, VA 22030, USA; (N.M.S.); (B.E.G.-G.); (H.D.)
| | - Blanca E. Gutiérrez-Guzmán
- Bioengineering Department, George Mason University, Fairfax, VA 22030, USA; (N.M.S.); (B.E.G.-G.); (H.D.)
| | - Holger Dannenberg
- Bioengineering Department, George Mason University, Fairfax, VA 22030, USA; (N.M.S.); (B.E.G.-G.); (H.D.)
- Interdisciplinary Program in Neuroscience, George Mason University, Fairfax, VA 22030, USA
| | - Giorgio A. Ascoli
- Bioengineering Department, George Mason University, Fairfax, VA 22030, USA; (N.M.S.); (B.E.G.-G.); (H.D.)
- Interdisciplinary Program in Neuroscience, George Mason University, Fairfax, VA 22030, USA
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2
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Sutton N, Gutiérrez-Guzmán B, Dannenberg H, Ascoli GA. A Continuous Attractor Model with Realistic Neural and Synaptic Properties Quantitatively Reproduces Grid Cell Physiology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.29.591748. [PMID: 38746202 PMCID: PMC11092518 DOI: 10.1101/2024.04.29.591748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Computational simulations with data-driven physiological detail can foster a deeper understanding of the neural mechanisms involved in cognition. Here, we utilize the wealth of cellular properties from Hippocampome.org to study neural mechanisms of spatial coding with a spiking continuous attractor network model of medial entorhinal cortex circuit activity. The primary goal was to investigate if adding such realistic constraints could produce firing patterns similar to those measured in real neurons. Biological characteristics included in the work are excitability, connectivity, and synaptic signaling of neuron types defined primarily by their axonal and dendritic morphologies. We investigate the spiking dynamics in specific neuron types and the synaptic activities between groups of neurons. Modeling the rodent hippocampal formation keeps the simulations to a computationally reasonable scale while also anchoring the parameters and results to experimental measurements. Our model generates grid cell activity that well matches the spacing, size, and firing rates of grid fields recorded in live behaving animals from both published datasets and new experiments performed for this study. Our simulations also recreate different scales of those properties, e.g., small and large, as found along the dorsoventral axis of the medial entorhinal cortex. Computational exploration of neuronal and synaptic model parameters reveals that a broad range of neural properties produce grid fields in the simulation. These results demonstrate that the continuous attractor network model of grid cells is compatible with a spiking neural network implementation sourcing data-driven biophysical and anatomical parameters from Hippocampome.org. The software is released as open source to enable broad community reuse and encourage novel applications.
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Affiliation(s)
- Nate Sutton
- Bioengineering Department, at George Mason University
| | | | - Holger Dannenberg
- Bioengineering Department, at George Mason University
- Interdisciplinary Program in Neuroscience at George Mason University
| | - Giorgio A. Ascoli
- Bioengineering Department, at George Mason University
- Interdisciplinary Program in Neuroscience at George Mason University
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3
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Bugaj AM, Kunath N, Saasen VL, Fernandez-Berrocal MS, Vankova A, Sætrom P, Bjørås M, Ye J. Dissecting gene expression networks in the developing hippocampus through the lens of NEIL3 depletion. Prog Neurobiol 2024; 235:102599. [PMID: 38522610 DOI: 10.1016/j.pneurobio.2024.102599] [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: 01/04/2024] [Revised: 03/09/2024] [Accepted: 03/19/2024] [Indexed: 03/26/2024]
Abstract
Gene regulation in the hippocampus is fundamental for its development, synaptic plasticity, memory formation, and adaptability. Comparisons of gene expression among different developmental stages, distinct cell types, and specific experimental conditions have identified differentially expressed genes contributing to the organization and functionality of hippocampal circuits. The NEIL3 DNA glycosylase, one of the DNA repair enzymes, plays an important role in hippocampal maturation and neuron functionality by shaping transcription. While differential gene expression (DGE) analysis has identified key genes involved, broader gene expression patterns crucial for high-order hippocampal functions remain uncharted. By utilizing the weighted gene co-expression network analysis (WGCNA), we mapped gene expression networks in immature (p8-neonatal) and mature (3 m-adult) hippocampal circuits in wild-type and NEIL3-deficient mice. Our study unveiled intricate gene network structures underlying hippocampal maturation, delineated modules of co-expressed genes, and pinpointed highly interconnected hub genes specific to the maturity of hippocampal subregions. We investigated variations within distinct gene network modules following NEIL3 depletion, uncovering NEIL3-targeted hub genes that influence module connectivity and specificity. By integrating WGCNA with DGE, we delve deeper into the NEIL3-dependent molecular intricacies of hippocampal maturation. This study provides a comprehensive systems-level analysis for assessing the potential correlation between gene connectivity and functional connectivity within the hippocampal network, thus shaping hippocampal function throughout development.
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Affiliation(s)
- Anna M Bugaj
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway
| | - Nicolas Kunath
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway; Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway; Department of Neurology, University Hospital of Trondheim, Trondheim 7491, Norway
| | - Vidar Langseth Saasen
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway
| | - Marion S Fernandez-Berrocal
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway
| | - Ana Vankova
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway
| | - Pål Sætrom
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway
| | - Magnar Bjørås
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway; Department of Microbiology, Oslo University Hospital, University of Oslo, Oslo 0424, Norway; Centre for Embryology and Healthy Development, University of Oslo, Oslo 0373, Norway.
| | - Jing Ye
- Department of Clinical and Molecular Medicine (IKOM), Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.
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4
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Chen L, Christenson Wick Z, Vetere LM, Vaughan N, Jurkowski A, Galas A, Diego KS, Philipsberg PA, Soler I, Feng Y, Cai DJ, Shuman T. Progressive Excitability Changes in the Medial Entorhinal Cortex in the 3xTg Mouse Model of Alzheimer's Disease Pathology. J Neurosci 2023; 43:7441-7454. [PMID: 37714705 PMCID: PMC10621765 DOI: 10.1523/jneurosci.1204-23.2023] [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: 06/29/2023] [Revised: 09/07/2023] [Accepted: 09/08/2023] [Indexed: 09/17/2023] Open
Abstract
Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by memory loss and progressive cognitive impairments. In mouse models of AD pathology, studies have found neuronal and synaptic deficits in hippocampus, but less is known about changes in medial entorhinal cortex (MEC), which is the primary spatial input to the hippocampus and an early site of AD pathology. Here, we measured neuronal intrinsic excitability and synaptic activity in MEC layer II (MECII) stellate cells, MECII pyramidal cells, and MEC layer III (MECIII) excitatory neurons at 3 and 10 months of age in the 3xTg mouse model of AD pathology, using male and female mice. At 3 months of age, before the onset of memory impairments, we found early hyperexcitability in intrinsic properties of MECII stellate and pyramidal cells, but this was balanced by a relative reduction in synaptic excitation (E) compared with inhibition (I; E/I ratio), suggesting intact homeostatic mechanisms regulating MECII activity. Conversely, MECIII neurons had reduced intrinsic excitability at this early time point with no change in synaptic E/I ratio. By 10 months of age, after the onset of memory deficits, neuronal excitability of MECII pyramidal cells and MECIII excitatory neurons was largely normalized in 3xTg mice. However, MECII stellate cells remained hyperexcitable, and this was further exacerbated by an increased synaptic E/I ratio. This observed combination of increased intrinsic and synaptic hyperexcitability suggests a breakdown in homeostatic mechanisms specifically in MECII stellate cells at this postsymptomatic time point, which may contribute to the emergence of memory deficits in AD.SIGNIFICANCE STATEMENT AD causes cognitive deficits, but the specific neural circuits that are damaged to drive changes in memory remain unknown. Using a mouse model of AD pathology that expresses both amyloid and tau transgenes, we found that neurons in the MEC have altered excitability. Before the onset of memory impairments, neurons in layer 2 of MEC had increased intrinsic excitability, but this was balanced by reduced inputs onto the cell. However, after the onset of memory impairments, stellate cells in MEC became further hyperexcitable, with increased excitability exacerbated by increased synaptic inputs. Thus, it appears that MEC stellate cells are uniquely disrupted during the progression of memory deficits and may contribute to cognitive deficits in AD.
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Affiliation(s)
- Lingxuan Chen
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, California 92697
| | - Zoé Christenson Wick
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Lauren M Vetere
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Nick Vaughan
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Albert Jurkowski
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
- Hunter College, City University of New York, New York, New York 10065
| | - Angelina Galas
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
- New York University, New York, New York 10012
| | - Keziah S Diego
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Paul A Philipsberg
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Ivan Soler
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Yu Feng
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Denise J Cai
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Tristan Shuman
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York 10029
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5
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Chen L, Wick ZC, Vetere LM, Vaughan N, Jurkowski A, Galas A, Diego KS, Philipsberg P, Cai DJ, Shuman T. Progressive excitability changes in the medial entorhinal cortex in the 3xTg mouse model of Alzheimer's disease pathology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.30.542838. [PMID: 37398359 PMCID: PMC10312508 DOI: 10.1101/2023.05.30.542838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Alzheimer's disease (AD) is a chronic neurodegenerative disorder that is characterized by memory loss and progressive cognitive impairments. In mouse models of AD pathology, studies have found neuronal and synaptic deficits in the hippocampus, but less is known about what happens in the medial entorhinal cortex (MEC), which is the primary spatial input to the hippocampus and an early site of AD pathology. Here, we measured the neuronal intrinsic excitability and synaptic activity in MEC layer II (MECII) stellate cells, MECII pyramidal cells, and MEC layer III (MECIII) excitatory neurons at early (3 months) and late (10 months) time points in the 3xTg mouse model of AD pathology. At 3 months of age, prior to the onset of memory impairments, we found early hyperexcitability in MECII stellate and pyramidal cells' intrinsic properties, but this was balanced by a relative reduction in synaptic excitation (E) compared to inhibition (I), suggesting intact homeostatic mechanisms regulating activity in MECII. Conversely, MECIII neurons had reduced intrinsic excitability at this early time point with no change in the synaptic E/I ratio. By 10 months of age, after the onset of memory deficits, neuronal excitability of MECII pyramidal cells and MECIII excitatory neurons was largely normalized in 3xTg mice. However, MECII stellate cells remained hyperexcitable and this was further exacerbated by an increased synaptic E/I ratio. This observed combination of increased intrinsically and synaptically generated excitability suggests a breakdown in homeostatic mechanisms specifically in MECII stellate cells at this post-symptomatic time point. Together, these data suggest that the breakdown in homeostatic excitability mechanisms in MECII stellate cells may contribute to the emergence of memory deficits in AD.
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Affiliation(s)
- Lingxuan Chen
- Icahn School of Medicine at Mount Sinai, New York NY
- University of California Irvine, Irvine CA
| | | | | | - Nick Vaughan
- Icahn School of Medicine at Mount Sinai, New York NY
| | - Albert Jurkowski
- Icahn School of Medicine at Mount Sinai, New York NY
- CUNY Hunter College, New York NY
| | - Angelina Galas
- Icahn School of Medicine at Mount Sinai, New York NY
- New York University, New York NY
| | | | | | - Denise J. Cai
- Icahn School of Medicine at Mount Sinai, New York NY
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Froula JM, Hastings SD, Krook-Magnuson E. The little brain and the seahorse: Cerebellar-hippocampal interactions. Front Syst Neurosci 2023; 17:1158492. [PMID: 37034014 PMCID: PMC10076554 DOI: 10.3389/fnsys.2023.1158492] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Accepted: 03/06/2023] [Indexed: 04/11/2023] Open
Abstract
There is a growing appreciation for the cerebellum beyond its role in motor function and accumulating evidence that the cerebellum and hippocampus interact across a range of brain states and behaviors. Acute and chronic manipulations, simultaneous recordings, and imaging studies together indicate coordinated coactivation and a bidirectional functional connectivity relevant for various physiological functions, including spatiotemporal processing. This bidirectional functional connectivity is likely supported by multiple circuit paths. It is also important in temporal lobe epilepsy: the cerebellum is impacted by seizures and epilepsy, and modulation of cerebellar circuitry can be an effective strategy to inhibit hippocampal seizures. This review highlights some of the recent key hippobellum literature.
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7
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McNamee DC, Stachenfeld KL, Botvinick MM, Gershman SJ. Compositional Sequence Generation in the Entorhinal-Hippocampal System. ENTROPY (BASEL, SWITZERLAND) 2022; 24:1791. [PMID: 36554196 PMCID: PMC9778317 DOI: 10.3390/e24121791] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 11/01/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
Neurons in the medial entorhinal cortex exhibit multiple, periodically organized, firing fields which collectively appear to form an internal representation of space. Neuroimaging data suggest that this grid coding is also present in other cortical areas such as the prefrontal cortex, indicating that it may be a general principle of neural functionality in the brain. In a recent analysis through the lens of dynamical systems theory, we showed how grid coding can lead to the generation of a diversity of empirically observed sequential reactivations of hippocampal place cells corresponding to traversals of cognitive maps. Here, we extend this sequence generation model by describing how the synthesis of multiple dynamical systems can support compositional cognitive computations. To empirically validate the model, we simulate two experiments demonstrating compositionality in space or in time during sequence generation. Finally, we describe several neural network architectures supporting various types of compositionality based on grid coding and highlight connections to recent work in machine learning leveraging analogous techniques.
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Affiliation(s)
- Daniel C. McNamee
- Neuroscience Programme, Champalimaud Research, 1400-038 Lisbon, Portugal
| | | | - Matthew M. Botvinick
- Google DeepMind, London N1C 4DN, UK
- Gatsby Computational Neuroscience Unit, University College London, London W1T 4JG, UK
| | - Samuel J. Gershman
- Department of Psychology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
- Center for Brains, Minds and Machines, MIT, Cambridge, MA 02139, USA
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8
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Machado JP, Athie MC, Matos AH, Lopes-Cendes I, Vieira A. The transcriptome of rat hippocampal subfields. IBRO Neurosci Rep 2022; 13:322-329. [PMID: 36247526 PMCID: PMC9561749 DOI: 10.1016/j.ibneur.2022.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 11/08/2022] Open
Abstract
The hippocampus comprises several neuronal populations such as CA1, CA2, CA3, and the dentate gyrus (DG), which present different neuronal origins, morphologies, and molecular mechanisms. Laser capture microdissection (LCM) allows selectively collecting samples from target regions and eliminating unwanted cells to obtain more specific results. LCM of hippocampus neuronal populations coupĺed with RNA-seq analysis has the potential to allow the exploration of the molecular machinery unique to each of these subfields. Previous RNA-seq investigation has already provided a molecular blueprint of the hippocampus, however, there is no RNA-seq data specific for each of the rat hippocampal regions. Serial tissue sections covering the hippocampus were produced from frozen brains of adult male Wistar rats, and the hippocampal subfields CA1, CA2, CA3, and DG were identified and isolated by LCM. We found evident segregation of the transcriptomic profile from different regions of the hippocampus and the expression of known, as well as novel, specific marker genes for each region. Gene ontology enrichment analysis of CA1 subfield indicates an enrichment of actin regulation and postsynaptic membrane AMPA receptors genes indispensable for long-term potentiation. CA2 and CA3 transcripts were found associated with the increased metabolic processes. DG expression was enriched for ribosome and spliceosome, both required for protein synthesis and maintenance of cell life. The present findings contribute to a deeper understanding of the differences in the molecular machinery expressed by the rat hippocampal neuronal populations, further exploring underlying mechanisms responsible for each subflied specific functions.
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Affiliation(s)
- João P.D. Machado
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology (BRAINN), Campinas, São Paulo, Brazil
| | - Maria C.P. Athie
- Department of Translational Medicine, School of Medical Sciences. University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology (BRAINN), Campinas, São Paulo, Brazil
| | - Alexandre H.B. Matos
- Department of Translational Medicine, School of Medical Sciences. University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology (BRAINN), Campinas, São Paulo, Brazil
| | - Iscia Lopes-Cendes
- Department of Translational Medicine, School of Medical Sciences. University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology (BRAINN), Campinas, São Paulo, Brazil
| | - André.S. Vieira
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
- Brazilian Institute of Neuroscience and Neurotechnology (BRAINN), Campinas, São Paulo, Brazil
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9
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Learning an Efficient Hippocampal Place Map from Entorhinal Inputs Using Non-Negative Sparse Coding. eNeuro 2021; 8:ENEURO.0557-20.2021. [PMID: 34162691 PMCID: PMC8266216 DOI: 10.1523/eneuro.0557-20.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 06/08/2021] [Accepted: 06/11/2021] [Indexed: 12/03/2022] Open
Abstract
Cells in the entorhinal cortex (EC) contain rich spatial information and project strongly to the hippocampus where a cognitive map is supposedly created. These cells range from cells with structured spatial selectivity, such as grid cells in the medial EC (MEC) that are selective to an array of spatial locations that form a hexagonal grid, to weakly spatial cells, such as non-grid cells in the MEC and lateral EC (LEC) that contain spatial information but have no structured spatial selectivity. However, in a small environment, place cells in the hippocampus are generally selective to a single location of the environment, while granule cells in the dentate gyrus of the hippocampus have multiple discrete firing locations but lack spatial periodicity. Given the anatomic connection from the EC to the hippocampus, how the hippocampus retrieves information from upstream EC remains unclear. Here, we propose a unified learning model that can describe the spatial tuning properties of both hippocampal place cells and dentate gyrus granule cells based on non-negative sparse coding from EC inputs. Sparse coding plays an important role in many cortical areas and is proposed here to have a key role in the hippocampus. Our results show that the hexagonal patterns of MEC grid cells with various orientations, grid spacings and phases are necessary for the model to learn different place cells that efficiently tile the entire spatial environment. However, if there is a lack of diversity in any grid parameters or a lack of hippocampal cells in the network, this will lead to the emergence of hippocampal cells that have multiple firing locations. More surprisingly, the model can also learn hippocampal place cells even when weakly spatial cells, instead of grid cells, are used as the input to the hippocampus. This work suggests that sparse coding may be one of the underlying organizing principles for the navigational system of the brain.
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10
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McNamee DC, Stachenfeld KL, Botvinick MM, Gershman SJ. Flexible modulation of sequence generation in the entorhinal-hippocampal system. Nat Neurosci 2021; 24:851-862. [PMID: 33846626 PMCID: PMC7610914 DOI: 10.1038/s41593-021-00831-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 03/03/2021] [Indexed: 02/01/2023]
Abstract
Exploration, consolidation and planning depend on the generation of sequential state representations. However, these algorithms require disparate forms of sampling dynamics for optimal performance. We theorize how the brain should adapt internally generated sequences for particular cognitive functions and propose a neural mechanism by which this may be accomplished within the entorhinal-hippocampal circuit. Specifically, we demonstrate that the systematic modulation along the medial entorhinal cortex dorsoventral axis of grid population input into the hippocampus facilitates a flexible generative process that can interpolate between qualitatively distinct regimes of sequential hippocampal reactivations. By relating the emergent hippocampal activity patterns drawn from our model to empirical data, we explain and reconcile a diversity of recently observed, but apparently unrelated, phenomena such as generative cycling, diffusive hippocampal reactivations and jumping trajectory events.
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Affiliation(s)
- Daniel C McNamee
- Wellcome Centre for Human Neuroimaging, University College London, London, UK.
- Max Planck UCL Centre for Computational Psychiatry, London, UK.
- Department of Psychology, Harvard University, Cambridge, MA, USA.
| | | | - Matthew M Botvinick
- Google DeepMind, London, UK
- Gatsby Computational Neuroscience Unit, University College London, London, UK
| | - Samuel J Gershman
- Department of Psychology, Harvard University, Cambridge, MA, USA
- Center for Brain Science, Harvard University, Cambridge, MA, USA
- Center for Brains, Minds and Machines, MIT, Cambridge, MA, USA
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11
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Bondi H, Bortolotto V, Canonico PL, Grilli M. Complex and regional-specific changes in the morphological complexity of GFAP + astrocytes in middle-aged mice. Neurobiol Aging 2021; 100:59-71. [PMID: 33493951 DOI: 10.1016/j.neurobiolaging.2020.12.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 12/14/2020] [Accepted: 12/19/2020] [Indexed: 02/06/2023]
Abstract
During aging, alterations in astrocyte phenotype occur in areas associated with age-related cognitive decline, including hippocampus. Previous work reported subregion-specific changes in surface, volume, and soma size of hippocampal astrocytes during physiological aging. Herein we extensively analyzed, by morphometric analysis, fine morphological features of GFAP+ astrocytes in young (6-month-old) and middle-aged (14-month-old) male mice. We observed remarkable heterogeneity in the astrocytic response to aging in distinct subfields and along the dorsoventral axis of hippocampus and in entorhinal cortex. In middle-aged mice dorsal granule cell and molecular layers, but not hilus, astrocytes underwent remarkable increase in their morphological complexity. These changes were absent in ventral Dentate Gyrus (DG). In addition, in entorhinal cortex, the major input to dorsal DG, astrocytes underwent remarkable atrophic changes in middle-aged mice. Since dorsal DG, and not ventral DG, is involved in cognitive functions, these findings appear worth of further evaluation. Our findings also suggest an additional level of complexity in the structural changes associated with brain aging.
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Affiliation(s)
- Heather Bondi
- Laboratory of Neuroplasticity, Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy; Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy
| | - Valeria Bortolotto
- Laboratory of Neuroplasticity, Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy; Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy
| | - Pier Luigi Canonico
- Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy
| | - Mariagrazia Grilli
- Laboratory of Neuroplasticity, Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy; Department of Pharmaceutical Sciences, University of Piemonte Orientale, Novara, Italy.
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12
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Signalling pathways contributing to learning and memory deficits in the Ts65Dn mouse model of Down syndrome. Neuronal Signal 2021; 5:NS20200011. [PMID: 33763235 PMCID: PMC7955101 DOI: 10.1042/ns20200011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 01/30/2023] Open
Abstract
Down syndrome (DS) is a genetic trisomic disorder that produces life-long changes in physiology and cognition. Many of the changes in learning and memory seen in DS are reminiscent of disorders involving the hippocampal/entorhinal circuit. Mouse models of DS typically involve trisomy of murine chromosome 16 is homologous for many of the genes triplicated in human trisomy 21, and provide us with good models of changes in, and potential pharmacotherapy for, human DS. Recent careful dissection of the Ts65Dn mouse model of DS has revealed differences in key signalling pathways from the basal forebrain to the hippocampus and associated rhinal cortices, as well as changes in the microstructure of the hippocampus itself. In vivo behavioural and electrophysiological studies have shown that Ts65Dn animals have difficulties in spatial memory that mirror hippocampal deficits, and have changes in hippocampal electrophysiological phenomenology that may explain these differences, and align with expectations generated from in vitro exploration of this model. Finally, given the existing data, we will examine the possibility for pharmacotherapy for DS, and outline the work that remains to be done to fully understand this system.
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Strategy-Specific Patterns of Arc Expression in the Retrosplenial Cortex and Hippocampus during T-Maze Learning in Rats. Brain Sci 2020; 10:brainsci10110854. [PMID: 33202708 PMCID: PMC7697392 DOI: 10.3390/brainsci10110854] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/04/2020] [Accepted: 11/10/2020] [Indexed: 11/16/2022] Open
Abstract
The retrosplenial cortex (RSC) belongs to the spatial memory circuit, but the precise timeline of its involvement and the relation to hippocampal activation have not been sufficiently described. We trained rats in a modified version of the T maze with transparent walls and distant visual cues to induce the formation of allocentric spatial memory. We used two distinct salient contexts associated with opposite sequences of turns. Switching between contexts allowed us to test the ability of animals to utilize spatial information. We then applied a CatFISH approach with a probe directed against the Arc immediate early gene in order to visualize the associated memory engrams in the RSC and the hippocampus. After training, rats displayed two strategies to solve the maze, with half of the animals relying on distant spatial cues (allocentric) and the other half using egocentric strategy. Rats that did not utilize the spatial cues showed higher Arc levels in the RSC compared to the allocentric group. The overlap between the two context engrams in the RSC was similar in both groups. These results show differential involvement of the RSC and hippocampus during spatial memory acquisition and point toward their distinct roles in forming the cognitive maps.
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14
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Malkemper EP, Nimpf S, Nordmann GC, Keays DA. Neuronal circuits and the magnetic sense: central questions. ACTA ACUST UNITED AC 2020; 223:223/21/jeb232371. [PMID: 33168544 DOI: 10.1242/jeb.232371] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Magnetoreception is the ability to sense the Earth's magnetic field, which is used for orientation and navigation. Behavioural experiments have shown that it is employed by many species across all vertebrate classes; however, our understanding of how magnetic information is processed and integrated within the central nervous system is limited. In this Commentary, we review the progress in birds and rodents, highlighting the role of the vestibular and trigeminal systems as well as that of the hippocampus. We reflect on the strengths and weaknesses of the methodologies currently at our disposal, the utility of emerging technologies and identify questions that we feel are critical for the advancement of the field. We expect that magnetic circuits are likely to share anatomical motifs with other senses, which culminates in the formation of spatial maps in telencephalic areas of the brain. Specifically, we predict the existence of spatial cells that encode defined components of the Earth's magnetic field.
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Affiliation(s)
- E Pascal Malkemper
- Max Planck Research Group Neurobiology of Magnetoreception, Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, Bonn 53175, Germany
| | - Simon Nimpf
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus Vienna Biocenter 1, Vienna 1030, Austria
| | - Gregory C Nordmann
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus Vienna Biocenter 1, Vienna 1030, Austria
| | - David A Keays
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus Vienna Biocenter 1, Vienna 1030, Austria .,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, VIC 3010, Australia.,Division of Neurobiology, Department Biology II, Ludwig-Maximilians-University Munich, Planegg-Martinsried 82152, Germany
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15
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Evidence for allocentric boundary and goal direction information in the human entorhinal cortex and subiculum. Nat Commun 2019; 10:4004. [PMID: 31488828 PMCID: PMC6728372 DOI: 10.1038/s41467-019-11802-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 08/01/2019] [Indexed: 12/15/2022] Open
Abstract
In rodents, cells in the medial entorhinal cortex (EC) and subiculum code for the allocentric direction to environment boundaries, which is an important prerequisite for accurate positional coding. Although in humans boundary-related signals have been reported, there is no evidence that they contain allocentric direction information. Furthermore, it has not been possible to separate boundary versus goal direction signals in the EC/subiculum. Here, to address these questions, we had participants learn a virtual environment containing four unique boundaries. Participants then underwent fMRI scanning where they made judgements about the allocentric direction of a cue object. Using multivariate decoding, we found information regarding allocentric boundary direction in posterior EC and subiculum, whereas allocentric goal direction was decodable from anterior EC and subiculum. These data provide the first evidence of allocentric boundary coding in humans, and are consistent with recent conceptualisations of a division of labour within the EC.
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16
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Gharib A, Komaki A, Manoochehri Khoshinani H, Saidijam M, Barkley V, Sarihi A, Mirnajafi-Zadeh J. Intrahippocampal 5-HT 1A receptor antagonist inhibits the improving effect of low-frequency stimulation on memory impairment in kindled rats. Brain Res Bull 2019; 148:109-117. [PMID: 30902574 DOI: 10.1016/j.brainresbull.2019.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 02/22/2019] [Accepted: 03/14/2019] [Indexed: 01/10/2023]
Abstract
In addition to its anticonvulsant effect, low frequency stimulation (LFS) improves learning and memory in kindled animals. In the present study, the role of 5-HT1A receptors in mediating LFS' improving effect on spatial learning and memory was investigated in amygdala-kindled rats. Amygdala kindling was conducted in a semi-rapid kindling stimulations (12 stimulations per day) in male Wistar rats. LFS (4 trains of 0.1 ms pulse duration at 1 Hz, 200 pulses, 50-150 μA, at 5 min intervals) was applied after termination of kindling stimulations. NAD-299 (a selective 5-HT1A receptor antagonist; 2.5 and 5 μg/μl) was microinjected into the hippocampal CA1 before applying LFS. The Morris water maze, and novel object recognition tests were conducted after the last kindling stimulation. Hippocampal samples were also prepared, and 5-HT1A receptor gene expression levels were assessed using quantitative RT-PCR. In kindled animals, LFS reduced impairments in spatial learning and memory in the Morris water maze and novel object recognition tests. Microinjection of NAD doses of 5 μg/μl reduced the effects of LFS on learning and memory. The gene expression level of 5-HT1A receptors increased significantly in the hippocampus of amygdala-kindled rats. However, LFS applied after kindling stimulations inhibited this effect. It seems that activation of 5-HT1A receptors in the CA1 field is necessary for LFS' improving effects on spatial learning and memory in kindled animals; although surprisingly, LFS application prevented the elevation in gene expression of 5-HT1A receptors in kindled animals.
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Affiliation(s)
- Alireza Gharib
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Alireza Komaki
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Hamed Manoochehri Khoshinani
- Department of Molecular Medicine and Genetics, School of Medicine, Hamedan University of Medical Sciences, Hamadan, Iran
| | - Massoud Saidijam
- Department of Molecular Medicine and Genetics, School of Medicine, Hamedan University of Medical Sciences, Hamadan, Iran
| | - Victoria Barkley
- Krembil Research Institute, University Health Network, Toronto, Canada
| | - Abdolrahman Sarihi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
| | - Javad Mirnajafi-Zadeh
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran; Institute for Brain Sciences and Cognition, Tarbiat Modares University, Tehran, Iran.
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17
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Robin J, Rai Y, Valli M, Olsen RK. Category specificity in the medial temporal lobe: A systematic review. Hippocampus 2018; 29:313-339. [PMID: 30155943 DOI: 10.1002/hipo.23024] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 08/03/2018] [Accepted: 08/07/2018] [Indexed: 01/30/2023]
Abstract
Theoretical accounts of medial temporal lobe (MTL) function ascribe different functions to subregions of the MTL including perirhinal, entorhinal, parahippocampal cortices, and the hippocampus. Some have suggested that the functional roles of these subregions vary in terms of their category specificity, showing preferential coding for certain stimulus types, but the evidence for this functional organization is mixed. In this systematic review, we evaluate existing evidence for regional specialization in the MTL for three categories of visual stimuli: faces, objects, and scenes. We review and synthesize across univariate and multivariate neuroimaging studies, as well as neuropsychological studies of cases with lesions to the MTL. Neuroimaging evidence suggests that faces activate the perirhinal cortex, entorhinal cortex, and the anterior hippocampus, while scenes engage the parahippocampal cortex and both the anterior and posterior hippocampus, depending on the contrast condition. There is some evidence for object-related activity in anterior MTL regions when compared to scenes, and in posterior MTL regions when compared to faces, suggesting that aspects of object representations may share similarities with face and scene representations. While neuroimaging evidence suggests some hippocampal specialization for faces and scenes, neuropsychological evidence shows that hippocampal damage leads to impairments in scene memory and perception, but does not entail equivalent impairments for faces in cases where the perirhinal cortex remains intact. Regional specialization based on stimulus categories has implications for understanding the mechanisms of MTL subregions, and highlights the need for the development of theoretical models of MTL function that can accommodate the differential patterns of specificity observed in the MTL.
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Affiliation(s)
- Jessica Robin
- Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada
| | - Yeshith Rai
- Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada
| | - Mikaeel Valli
- Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Rosanna K Olsen
- Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada.,Department of Psychology, University of Toronto, Toronto, Ontario, Canada
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18
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Stagni F, Giacomini A, Emili M, Uguagliati B, Bonasoni MP, Bartesaghi R, Guidi S. Subicular hypotrophy in fetuses with Down syndrome and in the Ts65Dn model of Down syndrome. Brain Pathol 2018; 29:366-379. [PMID: 30325080 DOI: 10.1111/bpa.12663] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 09/07/2018] [Accepted: 10/02/2018] [Indexed: 12/30/2022] Open
Abstract
Intellectual disability in Down syndrome (DS) has been attributed to neurogenesis impairment during fetal brain development. Consistently with explicit memory alterations observed in children with DS, fetuses with DS exhibit neurogenesis impairment in the hippocampus, a key region involved in memory formation and consolidation. Recent evidence suggests that the subiculum plays a unique role in memory retrieval, a process that is also altered in DS. While much attention has been devoted to the hippocampus, there is a striking lack of information regarding the subiculum of individuals with DS and DS models. In order to fill this gap, in the current study, we examined the subiculum of fetuses with DS and of the Ts65Dn mouse model of DS. We found that in fetuses with DS (gestational week: 17-21), the subiculum had a reduced thickness, a reduced cell density, a reduced density of progenitor cells in the ventricular zone, a reduced percentage of neurons, and an increased percentage of astrocytes and of cells immunopositive for calretinin-a protein expressed by inhibitory interneurons. Similarly to fetuses with DS, the subiculum of neonate Ts65Dn mice was reduced in size, had a reduced number of neurons and a reduced number of proliferating cells. Results suggest that the developmental defects in the subiculum of fetuses with DS may underlie impairment in recall memory and possibly other functions played by the subiculum. The finding that the subiculum of the Ts65Dn mouse exhibits neuroanatomical defects resembling those seen in fetuses with DS further validates the use of this model for preclinical studies.
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Affiliation(s)
- Fiorenza Stagni
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Andrea Giacomini
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Marco Emili
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Beatrice Uguagliati
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | | | - Renata Bartesaghi
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Sandra Guidi
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
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19
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Lee HW, Lee SM, Lee I. Neural Firing Patterns Are More Schematic and Less Sensitive to Changes in Background Visual Scenes in the Subiculum than in the Hippocampus. J Neurosci 2018; 38:7392-7408. [PMID: 30012689 PMCID: PMC6596140 DOI: 10.1523/jneurosci.0156-18.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 06/28/2018] [Accepted: 06/30/2018] [Indexed: 11/21/2022] Open
Abstract
Literature suggests that the hippocampus is central to processing visual scenes to remember contextual information, but the roles of its downstream structure, subiculum, remain unknown. Here, single units were recorded simultaneously in the dorsal CA1 and subiculum while male rats made spatial choices using visual scenes as cues in a T-maze. The firing fields of subicular neurons were schematically organized following the task structure, largely divided into pre-choice and post-choice epochs, whereas those of CA1 cells were more punctate and bound to specific locations. When the rats were tested with highly familiar scenes, neurons in the CA1 and subiculum were indistinguishable in coding the task-related information (e.g., scene, choice) through rate remapping. However, when the familiar scenes were blurred parametrically, the neurons in the CA1 responded sensitively to the novelty in task demand and changed its representations parametrically following the physical changes of the stimuli, whereas these functional characteristics were absent in the subiculum. These results suggest that the unique function of the hippocampus is to acquire contextual representations in association with discrete positions in space, especially when facing new and ambiguous scenes, whereas the subiculum may translate the position-bound visual contextual information of the hippocampus into schematic codes once learning is established.SIGNIFICANCE STATEMENT Although the potential functional significance has been recognized for decades for the subiculum, its exact roles in a goal-directed memory task still remain elusive. In the current study, we present experimental evidence that may indicate that the neural population in the subiculum could translate the location-bound spatial representations of the hippocampus into more schematic representations of task demands. Our findings also imply that the visual scene-based codes conveyed by the hippocampus and subiculum may be identical in a well learned task, whereas the hippocampus may be more specialized in representing altered visual scenes than the subiculum.
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Affiliation(s)
- Hyun-Woo Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Gwanak-gu, Seoul, Korea 08826
| | - Su-Min Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Gwanak-gu, Seoul, Korea 08826
| | - Inah Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Gwanak-gu, Seoul, Korea 08826
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20
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Hébert M, Anfray A, Chevilley A, Martinez de Lizarrondo S, Quenault A, Louessard M, Roussel BD, Obiang P, Save E, Orset C, Maubert E, Vivien D, Agin V. Distant Space Processing is Controlled by tPA-dependent NMDA Receptor Signaling in the Entorhinal Cortex. Cereb Cortex 2018; 27:4783-4796. [PMID: 27613436 DOI: 10.1093/cercor/bhw275] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 08/10/2016] [Indexed: 11/14/2022] Open
Abstract
In humans, spatial cognition and navigation impairments are a frequent situation during physiological and pathological aging, leading to a dramatic deterioration in the quality of life. Despite the discovery of neurons with location-specific activity in rodents, that is, place cells in the hippocampus and later on grid cells in the entorhinal cortex (EC), the molecular mechanisms underlying spatial cognition are still poorly known. Our present data bring together in an unusual combination 2 molecules of primary biological importance: a major neuronal excitatory receptor, N-methyl-D-aspartate receptor (NMDAR), and an extracellular protease, tissue plasminogen activator (tPA), in the control of spatial navigation. By using tPA-deficient mice and a structure-selective pharmacological approach, we demonstrate that the tPA-dependent NMDAR signaling potentiation in the EC plays a key and selective role in the encoding and the subsequent use of distant landmarks during spatial learning. We also demonstrate that this novel function of tPA in the EC is reduced during aging. Overall, these results argue for the concept that encoding of proximal versus distal landmarks is mediated not only by different anatomical pathways but also by different molecular mechanisms, with the tPA-dependent potentiation of NMDAR signaling in the EC that plays an important role.
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Affiliation(s)
- Marie Hébert
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Antoine Anfray
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Arnaud Chevilley
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Sara Martinez de Lizarrondo
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Aurélien Quenault
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Morgane Louessard
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Benoit D Roussel
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Pauline Obiang
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Etienne Save
- Laboratory of Cognitive Neuroscience UMR 7291, Aix-Marseille University, CNRS, 3 Place Victor Hugo, F-13331 Marseille Cedex 3, France
| | - Cyrille Orset
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Eric Maubert
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
| | - Denis Vivien
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France.,Biology Department, Clinical Research Department Medical Center, Normandie Université, UNICAEN, 14000 Caen, France
| | - Véronique Agin
- Normandie Univ, UNICAEN, INSERM, Sérine protéases et physiopathologie de l'unité neurovasculaire, 14000 Caen, France
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21
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Place and Grid Cells in a Loop: Implications for Memory Function and Spatial Coding. J Neurosci 2017; 37:8062-8076. [PMID: 28701481 DOI: 10.1523/jneurosci.3490-16.2017] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 05/25/2017] [Accepted: 05/27/2017] [Indexed: 11/21/2022] Open
Abstract
Place cells in the hippocampus and grid cells in the medial entorhinal cortex have different codes for space. However, how one code relates to the other is ill understood. Based on the anatomy of the entorhinal-hippocampal circuitry, we constructed a model of place and grid cells organized in a loop to investigate their mutual influence in the establishment of their codes for space. Using computer simulations, we first replicated experiments in rats that measured place and grid cell activity in different environments, and then assessed which features of the model account for different phenomena observed in neurophysiological data, such as pattern completion and pattern separation, global and rate remapping of place cells, and realignment of grid cells. We found that (1) the interaction between grid and place cells converges quickly; (2) the spatial code of place cells does not require, but is altered by, grid cell input; (3) plasticity in sensory inputs to place cells is key for pattern completion but not pattern separation; (4) grid realignment can be explained in terms of place cell remapping as opposed to the other way around; (5) the switch between global and rate remapping is self-organized; and (6) grid cell input to place cells helps stabilize their code under noisy and/or inconsistent sensory input. We conclude that the hippocampus-entorhinal circuit uses the mutual interaction of place and grid cells to encode the surrounding environment and propose a theory on how such interdependence underlies the formation and use of the cognitive map.SIGNIFICANCE STATEMENT The mammalian brain implements a positional system with two key pieces: place and grid cells. To gain insight into the dynamics of place and grid cell interaction, we built a computational model with the two cell types organized in a loop. The proposed model accounts for differences in how place and grid cells represent different environments and provides a new interpretation in which place and grid cells mutually interact to form a coupled code for space.
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22
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Hao X, Huang Y, Song Y, Kong X, Liu J. Experience with the Cardinal Coordinate System Contributes to the Precision of Cognitive Maps. Front Psychol 2017; 8:1166. [PMID: 28744248 PMCID: PMC5504278 DOI: 10.3389/fpsyg.2017.01166] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 06/26/2017] [Indexed: 01/15/2023] Open
Abstract
The coordinate system has been proposed as a fundamental and cross-culturally used spatial representation, through which people code location and direction information in the environment. Here we provided direct evidence demonstrating that daily experience with the cardinal coordinate system (i.e., east, west, north, and south) contributed to the representation of cognitive maps. Behaviorally, we found that individuals who relied more on the cardinal coordinate system for daily navigation made smaller errors in an indoor pointing task, suggesting that the cardinal coordinate system is an important element of cognitive maps. Neurally, the extent to which individuals relied on the cardinal coordinate system was positively correlated with the gray matter volume of the entorhinal cortex, suggesting that the entorhinal cortex may serve as the neuroanatomical basis of coordinate-based navigation (the entorhinal coordinate area, ECA). Further analyses on the resting-state functional connectivity revealed that the intrinsic interaction between the ECA and two hippocampal sub-regions, the subiculum and cornu ammonis, might be linked with the representation precision of cognitive maps. In sum, our study reveals an association between daily experience with the cardinal coordinate system and cognitive maps, and suggests that the ECA works in collaboration with hippocampal sub-regions to represent cognitive maps.
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Affiliation(s)
- Xin Hao
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal UniversityBeijing, China
| | - Yi Huang
- Department of Psychology, Tsinghua UniversityBeijing, China
| | - Yiying Song
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal UniversityBeijing, China
| | - Xiangzhen Kong
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, Beijing Normal UniversityBeijing, China
| | - Jia Liu
- Beijing Key Laboratory of Applied Experimental Psychology, School of Psychology, Beijing Normal UniversityBeijing, China
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23
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The Dendrites of CA2 and CA1 Pyramidal Neurons Differentially Regulate Information Flow in the Cortico-Hippocampal Circuit. J Neurosci 2017; 37:3276-3293. [PMID: 28213444 DOI: 10.1523/jneurosci.2219-16.2017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 12/27/2016] [Accepted: 02/07/2017] [Indexed: 12/29/2022] Open
Abstract
The impact of a given neuronal pathway depends on the number of synapses it makes with its postsynaptic target, the strength of each individual synapse, and the integrative properties of the postsynaptic dendrites. Here we explore the cellular and synaptic mechanisms responsible for the differential excitatory drive from the entorhinal cortical pathway onto mouse CA2 compared with CA1 pyramidal neurons (PNs). Although both types of neurons receive direct input from entorhinal cortex onto their distal dendrites, these inputs produce a 5- to 6-fold larger EPSP at the soma of CA2 compared with CA1 PNs, which is sufficient to drive action potential output from CA2 but not CA1. Experimental and computational approaches reveal that dendritic propagation is more efficient in CA2 than CA1 as a result of differences in dendritic morphology and dendritic expression of the hyperpolarization-activated cation current (Ih). Furthermore, there are three times as many cortical inputs onto CA2 compared with CA1 PN distal dendrites. Using a computational model, we demonstrate that the differences in dendritic properties of CA2 compared with CA1 PNs are necessary to enable the CA2 PNs to generate their characteristically large EPSPs in response to their cortical inputs; in contrast, CA1 dendritic properties limit the size of the EPSPs they generate, even to a similar number of cortical inputs. Thus, the matching of dendritic integrative properties with the density of innervation is crucial for the differential processing of information from the direct cortical inputs by CA2 compared with CA1 PNs.SIGNIFICANCE STATEMENT Recent discoveries have shown that the long-neglected hippocampal CA2 region has distinct synaptic properties and plays a prominent role in social memory and schizophrenia. This study addresses the puzzling finding that the direct entorhinal cortical inputs to hippocampus, which target the very distal pyramidal neuron dendrites, provide an unusually strong excitatory drive at the soma of CA2 pyramidal neurons, with EPSPs that are 5-6 times larger than those in CA1 pyramidal neurons. We here elucidate synaptic and dendritic mechanisms that account quantitatively for the marked difference in EPSP size. Our findings further demonstrate the general importance of fine-tuning the integrative properties of neuronal dendrites to their density of synaptic innervation.
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24
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Keene CS, Bladon J, McKenzie S, Liu CD, O'Keefe J, Eichenbaum H. Complementary Functional Organization of Neuronal Activity Patterns in the Perirhinal, Lateral Entorhinal, and Medial Entorhinal Cortices. J Neurosci 2016; 36:3660-75. [PMID: 27030753 PMCID: PMC4812128 DOI: 10.1523/jneurosci.4368-15.2016] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 02/16/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED It is commonly conceived that the cortical areas of the hippocampal region are functionally divided into the perirhinal cortex (PRC) and the lateral entorhinal cortex (LEC), which selectively process object information; and the medial entorhinal cortex (MEC), which selectively processes spatial information. Contrary to this notion, in rats performing a task that demands both object and spatial information processing, single neurons in PRC, LEC, and MEC, including those in both superficial and deep cortical areas and in grid, border, and head direction cells of MEC, have a highly similar range of selectivity to object and spatial dimensions of the task. By contrast, representational similarity analysis of population activity reveals a key distinction in the organization of information in these areas, such that PRC and LEC populations prioritize object over location information, whereas MEC populations prioritize location over object information. These findings bring to the hippocampal system a growing emphasis on population analyses as a powerful tool for characterizing neural representations supporting cognition and memory. SIGNIFICANCE STATEMENT Contrary to the common view that brain regions in the "what" and "where" streams distinctly process object and spatial cues, respectively, we found that both streams encode both object and spatial information but distinctly organize memories for objects and space. Specifically, perirhinal cortex and lateral entorhinal cortex represent objects and, within the object-specific representations, the locations where they occur. Conversely, medial entorhinal cortex represents relevant locations and, within those spatial representations, the objects that occupy them. Furthermore, these findings reach beyond simple notions of perirhinal cortex and lateral entorhinal cortex neurons as object detectors and MEC neurons as position detectors, and point to a more complex organization of memory representations within the medial temporal lobe system.
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Affiliation(s)
- Christopher S Keene
- Center for Memory and Brain, Boston University, Boston, Massachusetts 02215, and
| | - John Bladon
- Center for Memory and Brain, Boston University, Boston, Massachusetts 02215, and
| | - Sam McKenzie
- The Neuroscience Institute, New York University Langone Medical Center, New York, New York 10016
| | - Cindy D Liu
- Center for Memory and Brain, Boston University, Boston, Massachusetts 02215, and
| | - Joseph O'Keefe
- Center for Memory and Brain, Boston University, Boston, Massachusetts 02215, and
| | - Howard Eichenbaum
- Center for Memory and Brain, Boston University, Boston, Massachusetts 02215, and
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Abstract
The postrhinal cortex (POR) provides substantial input to the entorhinal cortex, mainly targeting superficial layers of the medial entorhinal cortex (MEC). Major inputs to POR originate in the visual and parietal cortex, thus providing neurons in MEC with a subset of cortical information relevant to their spatial firing properties. The POR takes a position that is comparable with that of the perirhinal cortex (PER) with regard to the lateral entorhinal cortex (LEC). Neurons in LEC and MEC show different functional properties likely reflecting differences in their respective inputs. Projections from PER to LEC exert a main inhibitory influence, which may relate to the sparse object-selective firing in LEC. In view of the continuous, spatially modulated firing properties of principal neurons in MEC, we tested in rats the hypothesis that projections from POR to MEC are functionally different from the PER-to-LEC counterpart in providing an excitatory drive to MEC. Our combined confocal and quantitative electron-microscopic observations indicated that POR projections target mainly principal cells in MEC, including neurons that project to the hippocampus. The ultrastructure of the majority of the synapses indicated that they are excitatory. Voltage-sensitive dye imaging in sagittal slices confirmed this morphologically derived conclusion, showing that the MEC network always responded with an overall depolarization, indicative for net excitatory transmission. In vitro single-cell recordings from principal cells showed only excitatory responses upon POR stimulation. These results show that POR provides an excitatory projection to MEC, differing fundamentally from the inhibitory projection of PER to LEC.
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Sugar J, Witter MP. Postnatal development of retrosplenial projections to the parahippocampal region of the rat. eLife 2016; 5:e13925. [PMID: 27008178 PMCID: PMC4859804 DOI: 10.7554/elife.13925] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/23/2016] [Indexed: 01/16/2023] Open
Abstract
The rat parahippocampal region (PHR) and retrosplenial cortex (RSC) are cortical areas important for spatial cognition. In PHR, head-direction cells are present before eye-opening, earliest detected in postnatal day (P)11 animals. Border cells have been recorded around eye-opening (P16), while grid cells do not obtain adult-like features until the fourth postnatal week. In view of these developmental time-lines, we aimed to explore when afferents originating in RSC arrive in PHR. To this end, we injected rats aged P0-P28 with anterograde tracers into RSC. First, we characterized the organization of RSC-PHR projections in postnatal rats and compared these results with data obtained in the adult. Second, we described the morphological development of axonal plexus in PHR. We conclude that the first arriving RSC-axons in PHR, present from P1 onwards, already show a topographical organization similar to that seen in adults, although the labeled plexus does not obtain adult-like densities until P12.
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Affiliation(s)
- Jørgen Sugar
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University for Science and Technology, Trondheim, Norway
| | - Menno P Witter
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University for Science and Technology, Trondheim, Norway
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Shima Y, Sugino K, Hempel CM, Shima M, Taneja P, Bullis JB, Mehta S, Lois C, Nelson SB. A Mammalian enhancer trap resource for discovering and manipulating neuronal cell types. eLife 2016; 5:e13503. [PMID: 26999799 PMCID: PMC4846381 DOI: 10.7554/elife.13503] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 03/18/2016] [Indexed: 12/16/2022] Open
Abstract
There is a continuing need for driver strains to enable cell-type-specific manipulation in the nervous system. Each cell type expresses a unique set of genes, and recapitulating expression of marker genes by BAC transgenesis or knock-in has generated useful transgenic mouse lines. However, since genes are often expressed in many cell types, many of these lines have relatively broad expression patterns. We report an alternative transgenic approach capturing distal enhancers for more focused expression. We identified an enhancer trap probe often producing restricted reporter expression and developed efficient enhancer trap screening with the PiggyBac transposon. We established more than 200 lines and found many lines that label small subsets of neurons in brain substructures, including known and novel cell types. Images and other information about each line are available online (enhancertrap.bio.brandeis.edu). DOI:http://dx.doi.org/10.7554/eLife.13503.001 Scientists can track and even alter the activity of different kinds of neurons, as well as the connections between neurons, by manipulating their genes. However, most genes are active in many different kinds of cells in many different places in the brain, making it difficult to track or target only a particular neuron or brain area. Enhancers are sections of DNA that can regulate the activity of nearby genes so that they are only active in very specific cell types, and an “enhancer trap” is a genetic approach that essentially hijacks enhancers to express artificial genes in those same cell types. The technique relies on inserting a genetic marker, which can be easily tracked, into random locations in the genome. If this marker then interacts with an enhancer, it is activated and the effect of the enhancer on gene expression can be assessed. This method has been used in fruit flies and fish to identify enhancers that specifically restrict gene expression to a small subset of cells. Now, Shima et al. show that enhancer traps can be used successfully in mammals too. The experiments produced over 200 different strains of mice, many with the fluorescent marker only in specific brain areas or in specific kinds of brain cells. Some of the types of brain cells uncovered by these experiments are new, and the labelling of specific brain cells and brain areas in different strains makes these mice a useful resource for future work. Furthermore, it will be relatively straightforward to produce many more strains of these mice, because it would simply involve crossbreeding mice. It is likely that some of these to-be-discovered strains will be useful tools for research as well. DOI:http://dx.doi.org/10.7554/eLife.13503.002
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Affiliation(s)
- Yasuyuki Shima
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Ken Sugino
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Chris Martin Hempel
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Masami Shima
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Praveen Taneja
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - James B Bullis
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Sonam Mehta
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
| | - Carlos Lois
- Division of Biology and Biological Engineering, Beckman Institute, California Institute of Technology, Pasadena, United States
| | - Sacha B Nelson
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, Waltham, United States
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Duzel E, van Praag H, Sendtner M. Can physical exercise in old age improve memory and hippocampal function? Brain 2016; 139:662-73. [PMID: 26912638 PMCID: PMC4766381 DOI: 10.1093/brain/awv407] [Citation(s) in RCA: 196] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 12/19/2015] [Accepted: 12/21/2015] [Indexed: 01/19/2023] Open
Abstract
Physical exercise can convey a protective effect against cognitive decline in ageing and Alzheimer's disease. While the long-term health-promoting and protective effects of exercise are encouraging, it's potential to induce neuronal and vascular plasticity in the ageing brain is still poorly understood. It remains unclear whether exercise slows the trajectory of normal ageing by modifying vascular and metabolic risk factors and/or consistently boosts brain function by inducing structural and neurochemical changes in the hippocampus and related medial temporal lobe circuitry-brain areas that are important for learning and memory. Hence, it remains to be established to what extent exercise interventions in old age can improve brain plasticity above and beyond preservation of function. Existing data suggest that exercise trials aiming for improvement and preservation may require different outcome measures and that the balance between the two may depend on exercise intensity and duration, the presence of preclinical Alzheimer's disease pathology, vascular and metabolic risk factors and genetic variability.
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Affiliation(s)
- Emrah Duzel
- 1 Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke University Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany 2 German Center for Neurodegenerative Diseases (DZNE), Leipziger Str. 44, 39120 Magdeburg, Germany 3 Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London, UK
| | - Henriette van Praag
- 4 Neuroplasticity and Behavior Unit, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Michael Sendtner
- 5 Institute of Clinical Neurobiology, University of Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
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29
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Calhoon GG, Tye KM. Resolving the neural circuits of anxiety. Nat Neurosci 2015; 18:1394-404. [PMID: 26404714 DOI: 10.1038/nn.4101] [Citation(s) in RCA: 432] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 07/30/2015] [Indexed: 12/12/2022]
Abstract
Although anxiety disorders represent a major societal problem demanding new therapeutic targets, these efforts have languished in the absence of a mechanistic understanding of this subjective emotional state. While it is impossible to know with certainty the subjective experience of a rodent, rodent models hold promise in dissecting well-conserved limbic circuits. The application of modern approaches in neuroscience has already begun to unmask the neural circuit intricacies underlying anxiety by allowing direct examination of hypotheses drawn from existing psychological concepts. This information points toward an updated conceptual model for what neural circuit perturbations could give rise to pathological anxiety and thereby provides a roadmap for future therapeutic development.
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Affiliation(s)
- Gwendolyn G Calhoon
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Kay M Tye
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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30
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Yuan RK, Hebert JC, Thomas AS, Wann EG, Muzzio IA. HDAC I inhibition in the dorsal and ventral hippocampus differentially modulates predator-odor fear learning and generalization. Front Neurosci 2015; 9:319. [PMID: 26441495 PMCID: PMC4585269 DOI: 10.3389/fnins.2015.00319] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/27/2015] [Indexed: 12/13/2022] Open
Abstract
Although predator odors are ethologically relevant stimuli for rodents, the molecular pathways and contribution of some brain regions involved in predator odor conditioning remain elusive. Inhibition of histone deacetylases (HDACs) in the dorsal hippocampus has been shown to enhance shock-induced contextual fear learning, but it is unknown if HDACs have differential effects along the dorso-ventral hippocampal axis during predator odor fear learning. We injected MS-275, a class I HDAC inhibitor, bilaterally in the dorsal or ventral hippocampus of mice and found that it had no effects on innate anxiety in either region. We then assessed the effects of MS-275 at different stages of fear learning along the longitudinal hippocampal axis. Animals were injected with MS-275 or vehicle after context pre-exposure (pre-conditioning injections), when a representation of the context is first formed, or after exposure to coyote urine (post-conditioning injections), when the context becomes associated with predator odor. When MS-275 was administered after context pre-exposure, dorsally injected animals showed enhanced fear in the training context but were able to discriminate it from a neutral environment. Conversely, ventrally injected animals did not display enhanced learning in the training context but generalized the fear response to a neutral context. However, when MS-275 was administered after conditioning, there were no differences between the MS-275 and vehicle control groups in either the dorsal or ventral hippocampus. Surprisingly, all groups displayed generalization to a neutral context, suggesting that predator odor exposure followed by a mild stressor such as restraint leads to fear generalization. These results may elucidate distinct functions of the dorsal and ventral hippocampus in predator odor-induced fear conditioning as well as some of the molecular mechanisms underlying fear generalization.
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Affiliation(s)
- Robin K Yuan
- Department of Psychology, University of Pennsylvania Philadelphia, PA, USA
| | - Jenna C Hebert
- Biological Basis of Behavior, University of Pennsylvania Philadelphia, PA, USA
| | - Arthur S Thomas
- Department of Biology, University of Pennsylvania Philadelphia, PA, USA
| | - Ellen G Wann
- Department of Psychology, University of Pennsylvania Philadelphia, PA, USA
| | - Isabel A Muzzio
- Department of Psychology, University of Pennsylvania Philadelphia, PA, USA ; Department of Biology, University of Texas at San Antonio San Antonio, TX, USA
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31
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Maass A, Berron D, Libby LA, Ranganath C, Düzel E. Functional subregions of the human entorhinal cortex. eLife 2015; 4. [PMID: 26052749 PMCID: PMC4458841 DOI: 10.7554/elife.06426] [Citation(s) in RCA: 156] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 05/06/2015] [Indexed: 11/13/2022] Open
Abstract
The entorhinal cortex (EC) is the primary site of interactions between the neocortex and hippocampus. Studies in rodents and nonhuman primates suggest that EC can be divided into subregions that connect differentially with perirhinal cortex (PRC) vs parahippocampal cortex (PHC) and with hippocampal subfields along the proximo-distal axis. Here, we used high-resolution functional magnetic resonance imaging at 7 Tesla to identify functional subdivisions of the human EC. In two independent datasets, PRC showed preferential intrinsic functional connectivity with anterior-lateral EC and PHC with posterior-medial EC. These EC subregions, in turn, exhibited differential connectivity with proximal and distal subiculum. In contrast, connectivity of PRC and PHC with subiculum followed not only a proximal-distal but also an anterior-posterior gradient. Our data provide the first evidence that the human EC can be divided into functional subdivisions whose functional connectivity closely parallels the known anatomical connectivity patterns of the rodent and nonhuman primate EC.
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Affiliation(s)
- Anne Maass
- Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - David Berron
- Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Laura A Libby
- Center for Neuroscience, University of California at Davis, Davis, United States
| | - Charan Ranganath
- Department of Psychology, University of California at Davis, Davis, United States
| | - Emrah Düzel
- German Center for Neurodegenerative Diseases, Magdeburg, Germany
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32
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Harland BC, Collings DA, McNaughton N, Abraham WC, Dalrymple-Alford JC. Anterior thalamic lesions reduce spine density in both hippocampal CA1 and retrosplenial cortex, but enrichment rescues CA1 spines only. Hippocampus 2014; 24:1232-47. [PMID: 24862603 DOI: 10.1002/hipo.22309] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2014] [Indexed: 12/14/2022]
Abstract
Injury to the anterior thalamic nuclei (ATN) may affect both hippocampus and retrosplenial cortex thus explaining some parallels between diencephalic and medial temporal lobe amnesias. We found that standard-housed rats with ATN lesions, compared with standard-housed controls, showed reduced spine density in hippocampal CA1 neurons (basal dendrites, -11.2%; apical dendrites, -9.6%) and in retrospenial granular b cortex (Rgb) neurons (apical dendrites, -20.1%) together with spatial memory deficits on cross maze and radial-arm maze tasks. Additional rats with ATN lesions were also shown to display a severe deficit on spatial working memory in the cross-maze, but subsequent enriched housing ameliorated their performance on both this task and the radial-arm maze. These enriched rats with ATN lesions also showed recovery of both basal and apical CA1 spine density to levels comparable to that of the standard-housed controls, but no recovery of Rgb spine density. Inspection of spine types in the CA1 neurons showed that ATN lesions reduced the density of thin spines and mushroom spines, but not stubby spines; while enrichment promoted recovery of thin spines. Comparison with enriched rats that received pseudo-training, which provided comparable task-related experience, but no explicit spatial memory training, suggested that basal CA1 spine density in particular was associated with spatial learning and memory performance. Distal pathology in terms of reduced integrity of hippocampal and retrosplenial microstructure provides clear support for the influence of the ATN lesions on the extended hippocampal system. The reversal by postoperative enrichment of this deficit in the hippocampus but not the retrosplenial cortex may indicate region-specific mechanisms of recovery after ATN injury.
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Affiliation(s)
- Bruce C Harland
- Department of Psychology, University of Canterbury, Christchurch, New Zealand
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33
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Hartley T, Lever C, Burgess N, O'Keefe J. Space in the brain: how the hippocampal formation supports spatial cognition. Philos Trans R Soc Lond B Biol Sci 2014; 369:20120510. [PMID: 24366125 PMCID: PMC3866435 DOI: 10.1098/rstb.2012.0510] [Citation(s) in RCA: 275] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Over the past four decades, research has revealed that cells in the hippocampal formation provide an exquisitely detailed representation of an animal's current location and heading. These findings have provided the foundations for a growing understanding of the mechanisms of spatial cognition in mammals, including humans. We describe the key properties of the major categories of spatial cells: place cells, head direction cells, grid cells and boundary cells, each of which has a characteristic firing pattern that encodes spatial parameters relating to the animal's current position and orientation. These properties also include the theta oscillation, which appears to play a functional role in the representation and processing of spatial information. Reviewing recent work, we identify some themes of current research and introduce approaches to computational modelling that have helped to bridge the different levels of description at which these mechanisms have been investigated. These range from the level of molecular biology and genetics to the behaviour and brain activity of entire organisms. We argue that the neuroscience of spatial cognition is emerging as an exceptionally integrative field which provides an ideal test-bed for theories linking neural coding, learning, memory and cognition.
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Affiliation(s)
- Tom Hartley
- Department of Psychology, University of York, York, UK
| | - Colin Lever
- Department of Psychology, University of Durham, Durham, UK
| | - Neil Burgess
- Institute of Cognitive Neuroscience and Institute of Neurology, University College London, London, UK
| | - John O'Keefe
- Sainsbury Wellcome Centre, University College London, London, UK
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34
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Knierim JJ, Neunuebel JP, Deshmukh SS. Functional correlates of the lateral and medial entorhinal cortex: objects, path integration and local-global reference frames. Philos Trans R Soc Lond B Biol Sci 2013; 369:20130369. [PMID: 24366146 DOI: 10.1098/rstb.2013.0369] [Citation(s) in RCA: 271] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The hippocampus receives its major cortical input from the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). It is commonly believed that the MEC provides spatial input to the hippocampus, whereas the LEC provides non-spatial input. We review new data which suggest that this simple dichotomy between 'where' versus 'what' needs revision. We propose a refinement of this model, which is more complex than the simple spatial-non-spatial dichotomy. MEC is proposed to be involved in path integration computations based on a global frame of reference, primarily using internally generated, self-motion cues and external input about environmental boundaries and scenes; it provides the hippocampus with a coordinate system that underlies the spatial context of an experience. LEC is proposed to process information about individual items and locations based on a local frame of reference, primarily using external sensory input; it provides the hippocampus with information about the content of an experience.
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Affiliation(s)
- James J Knierim
- Solomon H. Snyder Department of Neuroscience, Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, , Baltimore, MD 21218, USA
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