1
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Robinson JC, Ying J, Hasselmo ME, Brandon MP. Optogenetic silencing of medial septal GABAergic neurons disrupts grid cell spatial and temporal coding in the medial entorhinal cortex. Cell Rep 2024; 43:114590. [PMID: 39163200 DOI: 10.1016/j.celrep.2024.114590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 05/29/2024] [Accepted: 07/21/2024] [Indexed: 08/22/2024] Open
Abstract
The hippocampus and medial entorhinal cortex (MEC) form a cognitive map that facilitates spatial navigation. As part of this map, MEC grid cells fire in a repeating hexagonal pattern across an environment. This grid pattern relies on inputs from the medial septum (MS). The MS, and specifically GABAergic neurons, are essential for theta rhythm oscillations in the entorhinal-hippocampal network; however, the role of this population in grid cell function is unclear. To investigate this, we use optogenetics to inhibit MS-GABAergic neurons and observe that MS-GABAergic inhibition disrupts grid cell spatial periodicity. Grid cell spatial periodicity is disrupted during both optogenetic inhibition periods and short inter-stimulus intervals. In contrast, longer inter-stimulus intervals allow for the recovery of grid cell spatial firing. In addition, grid cell phase precession is also disrupted. These findings highlight the critical role of MS-GABAergic neurons in maintaining grid cell spatial and temporal coding in the MEC.
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Affiliation(s)
- Jennifer C Robinson
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, MA, USA.
| | - Johnson Ying
- Department of Psychiatry, Douglas Hospital Research Centre, McGill University, Montreal QC, Canada; Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
| | - Michael E Hasselmo
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, MA, USA
| | - Mark P Brandon
- Department of Psychiatry, Douglas Hospital Research Centre, McGill University, Montreal QC, Canada; Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada.
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2
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Tan E, Troller-Renfree SV, Morales S, Buzzell GA, McSweeney M, Antúnez M, Fox NA. Theta activity and cognitive functioning: Integrating evidence from resting-state and task-related developmental electroencephalography (EEG) research. Dev Cogn Neurosci 2024; 67:101404. [PMID: 38852382 PMCID: PMC11214181 DOI: 10.1016/j.dcn.2024.101404] [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: 11/02/2023] [Revised: 05/28/2024] [Accepted: 06/06/2024] [Indexed: 06/11/2024] Open
Abstract
The theta band is one of the most prominent frequency bands in the electroencephalography (EEG) power spectrum and presents an interesting paradox: while elevated theta power during resting state is linked to lower cognitive abilities in children and adolescents, increased theta power during cognitive tasks is associated with higher cognitive performance. Why does theta power, measured during resting state versus cognitive tasks, show differential correlations with cognitive functioning? This review provides an integrated account of the functional correlates of theta across different contexts. We first present evidence that higher theta power during resting state is correlated with lower executive functioning, attentional abilities, language skills, and IQ. Next, we review research showing that theta power increases during memory, attention, and cognitive control, and that higher theta power during these processes is correlated with better performance. Finally, we discuss potential explanations for the differential correlations between resting/task-related theta and cognitive functioning, and offer suggestions for future research in this area.
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Affiliation(s)
- Enda Tan
- Department of Human Development and Quantitative Methodology, University of Maryland, College Park, MD 20740, USA; Neuroscience and Cognitive Science Program, University of Maryland, College Park, MD 20740, USA.
| | | | - Santiago Morales
- Department of Psychology, University of Southern California, CA 90007, USA
| | - George A Buzzell
- Department of Psychology, Florida International University, FL 33199, USA
| | - Marco McSweeney
- Department of Human Development and Quantitative Methodology, University of Maryland, College Park, MD 20740, USA
| | - Martín Antúnez
- Department of Human Development and Quantitative Methodology, University of Maryland, College Park, MD 20740, USA
| | - Nathan A Fox
- Department of Human Development and Quantitative Methodology, University of Maryland, College Park, MD 20740, USA; Neuroscience and Cognitive Science Program, University of Maryland, College Park, MD 20740, USA
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3
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Robinson JC, Ying J, Hasselmo ME, Brandon MP. Optogenetic Silencing of Medial Septal GABAergic Neurons Disrupts Grid Cell Spatial and Temporal Coding in the Medial Entorhinal Cortex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.566228. [PMID: 37986986 PMCID: PMC10659309 DOI: 10.1101/2023.11.08.566228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
The hippocampus and medial entorhinal cortex (MEC) form a cognitive map that facilitates spatial navigation. As part of this map, MEC grid cells fire in a repeating hexagonal pattern across an environment. This grid pattern relies on inputs from the medial septum (MS). The MS, and specifically its GABAergic neurons, are essential for theta rhythm oscillations in the entorhinal-hippocampal network, however, it is unknown if this subpopulation is also essential for grid cell function. To investigate this, we used optogenetics to inhibit MS-GABAergic neurons during grid cell recordings. We found that MS-GABAergic inhibition disrupted grid cell spatial periodicity both during optogenetic inhibition and during short 30-second recovery periods. Longer recovery periods of 60 seconds between the optogenetic inhibition periods allowed for the recovery of grid cell spatial firing. Grid cell temporal coding was also disrupted, as observed by a significant attenuation of theta phase precession. Together, these results demonstrate that MS-GABAergic neurons are critical for grid cell spatial and temporal coding in the MEC.
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4
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Király B, Domonkos A, Jelitai M, Lopes-Dos-Santos V, Martínez-Bellver S, Kocsis B, Schlingloff D, Joshi A, Salib M, Fiáth R, Barthó P, Ulbert I, Freund TF, Viney TJ, Dupret D, Varga V, Hangya B. The medial septum controls hippocampal supra-theta oscillations. Nat Commun 2023; 14:6159. [PMID: 37816713 PMCID: PMC10564782 DOI: 10.1038/s41467-023-41746-0] [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: 07/27/2022] [Accepted: 09/15/2023] [Indexed: 10/12/2023] Open
Abstract
Hippocampal theta oscillations orchestrate faster beta-to-gamma oscillations facilitating the segmentation of neural representations during navigation and episodic memory. Supra-theta rhythms of hippocampal CA1 are coordinated by local interactions as well as inputs from the entorhinal cortex (EC) and CA3 inputs. However, theta-nested gamma-band activity in the medial septum (MS) suggests that the MS may control supra-theta CA1 oscillations. To address this, we performed multi-electrode recordings of MS and CA1 activity in rodents and found that MS neuron firing showed strong phase-coupling to theta-nested supra-theta episodes and predicted changes in CA1 beta-to-gamma oscillations on a cycle-by-cycle basis. Unique coupling patterns of anatomically defined MS cell types suggested that indirect MS-to-CA1 pathways via the EC and CA3 mediate distinct CA1 gamma-band oscillations. Optogenetic activation of MS parvalbumin-expressing neurons elicited theta-nested beta-to-gamma oscillations in CA1. Thus, the MS orchestrates hippocampal network activity at multiple temporal scales to mediate memory encoding and retrieval.
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Affiliation(s)
- Bálint Király
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary
- Department of Biological Physics, Institute of Physics, Eötvös Loránd University, Budapest, Hungary
| | - Andor Domonkos
- Subcortical Modulation Research Group, Institute of Experimental Medicine, Budapest, Hungary
| | - Márta Jelitai
- Subcortical Modulation Research Group, Institute of Experimental Medicine, Budapest, Hungary
| | - Vítor Lopes-Dos-Santos
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Sergio Martínez-Bellver
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary
- Department of Anatomy and Human Embryology, Faculty of Medicine and Odontology, University of Valencia, Valencia, Spain
| | - Barnabás Kocsis
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary
- Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
| | - Dániel Schlingloff
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary
| | - Abhilasha Joshi
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Minas Salib
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Richárd Fiáth
- Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
- Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Péter Barthó
- Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Budapest, Hungary
| | - István Ulbert
- Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
- Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Tamás F Freund
- Laboratory of Cerebral Cortex Research, Institute of Experimental Medicine, Budapest, Hungary
| | - Tim J Viney
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - David Dupret
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Viktor Varga
- Subcortical Modulation Research Group, Institute of Experimental Medicine, Budapest, Hungary
| | - Balázs Hangya
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary.
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5
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Robinson JC, Wilmot JH, Hasselmo ME. Septo-hippocampal dynamics and the encoding of space and time. Trends Neurosci 2023; 46:712-725. [PMID: 37479632 PMCID: PMC10538955 DOI: 10.1016/j.tins.2023.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 05/12/2023] [Accepted: 06/27/2023] [Indexed: 07/23/2023]
Abstract
Encoding an event in memory requires neural activity to represent multiple dimensions of behavioral experience in space and time. Recent experiments have explored the influence of neural dynamics regulated by the medial septum on the functional encoding of space and time by neurons in the hippocampus and associated structures. This review addresses these dynamics, focusing on the role of theta rhythm, the differential effects of septal inactivation and activation on the functional coding of space and time by individual neurons, and the influence on phase coding that appears as phase precession. We also discuss data indicating that theta rhythm plays a role in timing the internal dynamics of memory encoding and retrieval, as well as the behavioral influences of these neuronal manipulations with regard to memory function.
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Affiliation(s)
- Jennifer C Robinson
- Center for Systems Neuroscience, Boston University, 610 Commonwealth Avenue, Boston, MA 02215, USA.
| | - Jacob H Wilmot
- Center for Systems Neuroscience, Boston University, 610 Commonwealth Avenue, Boston, MA 02215, USA.
| | - Michael E Hasselmo
- Center for Systems Neuroscience, Boston University, 610 Commonwealth Avenue, Boston, MA 02215, USA.
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6
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George TM, de Cothi W, Stachenfeld KL, Barry C. Rapid learning of predictive maps with STDP and theta phase precession. eLife 2023; 12:e80663. [PMID: 36927826 PMCID: PMC10019887 DOI: 10.7554/elife.80663] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 02/26/2023] [Indexed: 03/18/2023] Open
Abstract
The predictive map hypothesis is a promising candidate principle for hippocampal function. A favoured formalisation of this hypothesis, called the successor representation, proposes that each place cell encodes the expected state occupancy of its target location in the near future. This predictive framework is supported by behavioural as well as electrophysiological evidence and has desirable consequences for both the generalisability and efficiency of reinforcement learning algorithms. However, it is unclear how the successor representation might be learnt in the brain. Error-driven temporal difference learning, commonly used to learn successor representations in artificial agents, is not known to be implemented in hippocampal networks. Instead, we demonstrate that spike-timing dependent plasticity (STDP), a form of Hebbian learning, acting on temporally compressed trajectories known as 'theta sweeps', is sufficient to rapidly learn a close approximation to the successor representation. The model is biologically plausible - it uses spiking neurons modulated by theta-band oscillations, diffuse and overlapping place cell-like state representations, and experimentally matched parameters. We show how this model maps onto known aspects of hippocampal circuitry and explains substantial variance in the temporal difference successor matrix, consequently giving rise to place cells that demonstrate experimentally observed successor representation-related phenomena including backwards expansion on a 1D track and elongation near walls in 2D. Finally, our model provides insight into the observed topographical ordering of place field sizes along the dorsal-ventral axis by showing this is necessary to prevent the detrimental mixing of larger place fields, which encode longer timescale successor representations, with more fine-grained predictions of spatial location.
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Affiliation(s)
- Tom M George
- Sainsbury Wellcome Centre for Neural Circuits and Behaviour, University College LondonLondonUnited Kingdom
| | - William de Cothi
- Research Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | | | - Caswell Barry
- Research Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
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7
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Deep Brain Stimulation of the Medial Septal Area Can Modulate Gene Expression in the Hippocampus of Rats under Urethane Anesthesia. Int J Mol Sci 2022; 23:ijms23116034. [PMID: 35682713 PMCID: PMC9181580 DOI: 10.3390/ijms23116034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 05/21/2022] [Accepted: 05/23/2022] [Indexed: 11/17/2022] Open
Abstract
We studied the effects of stimulation of the medial septal area on the gene expression in the dorsal and ventral hippocampus. Rats under urethane anesthesia were implanted with a recording electrode in the right hippocampus and stimulating electrode in the dorsal medial septum (dMS) or medial septal nucleus (MSN). After one-hour-long deep brain stimulation, we collected ipsi- and contralateral dorsal and ventral hippocampi. Quantitative PCR showed that deep brain stimulation did not cause any changes in the intact contralateral dorsal and ventral hippocampi. A comparison of ipsi- and contralateral hippocampi in the control unstimulated animals showed that electrode implantation in the ipsilateral dorsal hippocampus led to a dramatic increase in the expression of immediate early genes (c-fos, arc, egr1, npas4), neurotrophins (ngf, bdnf) and inflammatory cytokines (il1b and tnf, but not il6) not only in the area close to implantation site but also in the ventral hippocampus. Moreover, the stimulation of MSN but not dMS further increased the expression of c-fos, egr1, npas4, bdnf, and tnf in the ipsilateral ventral but not dorsal hippocampus. Our data suggest that the activation of medial septal nucleus can change the gene expression in ventral hippocampal cells after their priming by other stimuli.
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8
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Li Y, Wei S, Liu Q, Gong Q, Zhang Q, Zheng T, Yong Z, Chen F, Lawrence AJ, Liang J. Mu-opioid receptors in septum mediate the development of behavioural sensitization to a single morphine exposure in male rats. Addict Biol 2022; 27:e13066. [PMID: 34030217 DOI: 10.1111/adb.13066] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 05/01/2021] [Accepted: 05/17/2021] [Indexed: 12/14/2022]
Abstract
Behavioural sensitization (BS) is characterized by enhanced psychomotor responses to a dose of substance of abuse after prior repeated exposure. We previously reported that BS can be induced by a single injection of morphine in rats, whereas septal nuclei are specifically involved in the development phase of BS. Here, we demonstrated that intra-LS or intra-MS microinjections also incubated BS to a systemic morphine injection in a cross-sensitization fashion, whereas inactivation of either subdivision of septal nuclei (LS: lateral septum; MS: medial septum) can negate this ability of morphine. Then, non-selective (naloxone) and selective (μ-, δ- and κ-)opioid receptor antagonists were directly delivered into LS or MS, respectively, ahead of a morphine microinjection, whereas only μ-opioid receptors in both LS and MS play indispensable roles in mediating the BS development. Finally, there was a pronounced elevation in the levels of the monoamines (i.e. dopamine, homovanillic acid, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid) in the septum, 8 h after a morphine injection detected with a HPLC-ECD method, suggesting that dopaminergi and serotoninergic systems are implicated in the BS formation. Our studies demonstrated that septal nuclei critically participate in the BS development. Essentially, μ- instead of δ- or κ-opioid receptors in LS and MS mediate sensitization to opiates.
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Affiliation(s)
- Yu‐Ling Li
- Department of Pharmacology, School of Basic Medical Sciences Peking University Beijing China
- Department of Pharmacy, East Hospital Tongji University School of Medicine Shanghai China
| | - Shoupeng Wei
- Department of Pharmacology, School of Basic Medical Sciences Peking University Beijing China
- The Seventh Affiliated Hospital Sun Yat‐sen University Shenzhen China
| | - Qing Liu
- Department of Pharmacology, School of Basic Medical Sciences Peking University Beijing China
| | - Qi Gong
- Department of Pharmacology, School of Basic Medical Sciences Peking University Beijing China
| | - Qing‐Jie Zhang
- Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences Peking University Beijing China
| | - Tian‐Ge Zheng
- Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences Peking University Beijing China
| | - Zheng Yong
- Beijing Institute of Pharmacology and Toxicology Academy of Military Medical Sciences Beijing China
| | - Feng Chen
- The Florey Institute of Neuroscience and Mental Health University of Melbourne Parkville Victoria Australia
| | - Andrew J. Lawrence
- The Florey Institute of Neuroscience and Mental Health University of Melbourne Parkville Victoria Australia
| | - Jian‐Hui Liang
- Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences Peking University Beijing China
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9
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Do Q, Hasselmo ME. Neural circuits and symbolic processing. Neurobiol Learn Mem 2021; 186:107552. [PMID: 34763073 PMCID: PMC10121157 DOI: 10.1016/j.nlm.2021.107552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 10/14/2021] [Accepted: 11/02/2021] [Indexed: 11/29/2022]
Abstract
The ability to use symbols is a defining feature of human intelligence. However, neuroscience has yet to explain the fundamental neural circuit mechanisms for flexibly representing and manipulating abstract concepts. This article will review the research on neural models for symbolic processing. The review first focuses on the question of how symbols could possibly be represented in neural circuits. The review then addresses how neural symbolic representations could be flexibly combined to meet a wide range of reasoning demands. Finally, the review assesses the research on program synthesis and proposes that the most flexible neural representation of symbolic processing would involve the capacity to rapidly synthesize neural operations analogous to lambda calculus to solve complex cognitive tasks.
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Affiliation(s)
- Quan Do
- Center for Systems Neuroscience, Boston University, 610 Commonwealth Ave, Boston, MA 02215, United States.
| | - Michael E Hasselmo
- Center for Systems Neuroscience, Boston University, 610 Commonwealth Ave, Boston, MA 02215, United States.
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10
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Quirk CR, Zutshi I, Srikanth S, Fu ML, Marciano ND, Wright MK, Parsey DF, Liu S, Siretskiy RE, Huynh TL, Leutgeb JK, Leutgeb S. Precisely timed theta oscillations are selectively required during the encoding phase of memory. Nat Neurosci 2021; 24:1614-1627. [PMID: 34608335 PMCID: PMC8556344 DOI: 10.1038/s41593-021-00919-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 08/02/2021] [Indexed: 11/12/2022]
Abstract
Brain oscillations have been hypothesized to support cognitive function by coordinating spike timing within and across brain regions, yet it is often not known when timing is either critical for neural computations or an epiphenomenon. The entorhinal cortex and hippocampus are necessary for learning and memory and exhibit prominent theta oscillations (6-9 Hz), which are controlled by pacemaker cells in the medial septal area. Here we show that entorhinal and hippocampal neuronal activity patterns were strongly entrained by rhythmic optical stimulation of parvalbumin-positive medial septal area neurons in mice. Despite strong entrainment, memory impairments in a spatial working memory task were not observed with pacing frequencies at or below the endogenous theta frequency and only emerged at frequencies ≥10 Hz, and specifically when pacing was targeted to maze segments where encoding occurs. Neural computations during the encoding phase were therefore selectively disrupted by perturbations of the timing of neuronal firing patterns.
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Affiliation(s)
- Clare R. Quirk
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ipshita Zutshi
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Sunandha Srikanth
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Maylin L. Fu
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Naomie Devico Marciano
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Morgan K. Wright
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Darian F. Parsey
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stanley Liu
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Rachel E. Siretskiy
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Tiffany L. Huynh
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jill K. Leutgeb
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stefan Leutgeb
- Neurobiology Section and Center for Neural Circuits and Behavior, University of California, San Diego, La Jolla, CA 92093, USA,Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA 92093, USA,Correspondence should be addressed to S.L. ()
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11
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Mocellin P, Mikulovic S. The Role of the Medial Septum-Associated Networks in Controlling Locomotion and Motivation to Move. Front Neural Circuits 2021; 15:699798. [PMID: 34366795 PMCID: PMC8340000 DOI: 10.3389/fncir.2021.699798] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Accepted: 06/28/2021] [Indexed: 12/29/2022] Open
Abstract
The Medial Septum and diagonal Band of Broca (MSDB) was initially studied for its role in locomotion. However, the last several decades were focussed on its intriguing function in theta rhythm generation. Early studies relied on electrical stimulation, lesions and pharmacological manipulation, and reported an inconclusive picture regarding the role of the MSDB circuits. Recent studies using more specific methodologies have started to elucidate the differential role of the MSDB's specific cell populations in controlling both theta rhythm and behaviour. In particular, a novel theory is emerging showing that different MSDB's cell populations project to different brain regions and control distinct aspects of behaviour. While the majority of these behaviours involve movement, increasing evidence suggests that MSDB-related networks govern the motivational aspect of actions, rather than locomotion per se. Here, we review the literature that links MSDB, theta activity, and locomotion and propose open questions, future directions, and methods that could be employed to elucidate the diverse roles of the MSDB-associated networks.
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Affiliation(s)
- Petra Mocellin
- Department of Cellular Neuroscience, Leibniz Institute for Neurobiology, Magdeburg, Germany
- International Max Planck Research School for Brain and Behavior, Bonn, Germany
| | - Sanja Mikulovic
- Research Group Cognition and Emotion, Leibniz Institute for Neurobiology, Magdeburg, Germany
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12
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Dannenberg H, Lazaro H, Nambiar P, Hoyland A, Hasselmo ME. Effects of visual inputs on neural dynamics for coding of location and running speed in medial entorhinal cortex. eLife 2020; 9:62500. [PMID: 33300873 PMCID: PMC7773338 DOI: 10.7554/elife.62500] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 12/09/2020] [Indexed: 12/13/2022] Open
Abstract
Neuronal representations of spatial location and movement speed in the medial entorhinal cortex during the ‘active’ theta state of the brain are important for memory-guided navigation and rely on visual inputs. However, little is known about how visual inputs change neural dynamics as a function of running speed and time. By manipulating visual inputs in mice, we demonstrate that changes in spatial stability of grid cell firing correlate with changes in a proposed speed signal by local field potential theta frequency. In contrast, visual inputs do not alter the running speed-dependent gain in neuronal firing rates. Moreover, we provide evidence that sensory inputs other than visual inputs can support grid cell firing, though less accurately, in complete darkness. Finally, changes in spatial accuracy of grid cell firing on a 10 s time scale suggest that grid cell firing is a function of velocity signals integrated over past time.
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Affiliation(s)
- Holger Dannenberg
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, United States
| | - Hallie Lazaro
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, United States
| | - Pranav Nambiar
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, United States
| | - Alec Hoyland
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, United States
| | - Michael E Hasselmo
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, United States
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13
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Melzer S, Monyer H. Diversity and function of corticopetal and corticofugal GABAergic projection neurons. Nat Rev Neurosci 2020; 21:499-515. [PMID: 32747763 DOI: 10.1038/s41583-020-0344-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2020] [Indexed: 12/27/2022]
Abstract
It is still widely thought that cortical projections to distant brain areas derive by and large from glutamatergic neurons. However, an increasing number of reports provide evidence that cortical GABAergic neurons comprise a smaller population of 'projection neurons' in addition to the well-known and much-studied interneurons. GABAergic long-range axons that derive from, or project to, cortical areas are thought to entrain distant brain areas for efficient information transfer and processing. Research conducted over the past 10 years has revealed that cortical GABAergic projection neurons are highly diverse in terms of molecular marker expression, synaptic targeting (identity of targeted cell types), activity pattern during distinct behavioural states and precise temporal recruitment relative to ongoing neuronal network oscillations. As GABAergic projection neurons connect many cortical areas unidirectionally or bidirectionally, it is safe to assume that they participate in the modulation of a whole series of behavioural and cognitive functions. We expect future research to examine how long-range GABAergic projections fine-tune activity in distinct distant networks and how their recruitment alters the behaviours that are supported by these networks.
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Affiliation(s)
- Sarah Melzer
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, USA
| | - Hannah Monyer
- Department of Clinical Neurobiology of the Medical Faculty of Heidelberg University and German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany.
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14
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Petersen PC, Buzsáki G. Cooling of Medial Septum Reveals Theta Phase Lag Coordination of Hippocampal Cell Assemblies. Neuron 2020; 107:731-744.e3. [PMID: 32526196 DOI: 10.1016/j.neuron.2020.05.023] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 04/26/2020] [Accepted: 05/16/2020] [Indexed: 12/31/2022]
Abstract
Hippocampal theta oscillations coordinate neuronal firing to support memory and spatial navigation. The medial septum (MS) is critical in theta generation by two possible mechanisms: either a unitary "pacemaker" timing signal is imposed on the hippocampal system, or it may assist in organizing target subcircuits within the phase space of theta oscillations. We used temperature manipulation of the MS to test these models. Cooling of the MS reduced both theta frequency and power and was associated with an enhanced incidence of errors in a spatial navigation task, but it did not affect spatial correlates of neurons. MS cooling decreased theta frequency oscillations of place cells and reduced distance-time compression but preserved distance-phase compression of place field sequences within the theta cycle. Thus, the septum is critical for sustaining precise theta phase coordination of cell assemblies in the hippocampal system, a mechanism needed for spatial memory.
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Affiliation(s)
| | - György Buzsáki
- Neuroscience Institute, NYU Langone, New York University, New York, NY 10016, USA; Department of Neurology, NYU Langone, New York University, New York, NY 10016, USA; Center for Neural Science, New York University, New York, NY 10003, USA.
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15
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Lee SL(T, Lew D, Wickenheisser V, Markus EJ. Interdependence between dorsal and ventral hippocampus during spatial navigation. Brain Behav 2019; 9:e01410. [PMID: 31571397 PMCID: PMC6790314 DOI: 10.1002/brb3.1410] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 08/15/2019] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION The hippocampus is linked to the formation and retrieval of episodic memories and spatial navigation. In rats, it is an elongated structure divided into dorsal (septal) and ventral (temporal) regions paralleling the respective division in the posterior and anterior hippocampus in humans. The dorsal hippocampus has been suggested to be more important for spatial processing and the ventral to processing anxiety-based behaviors. Far less is known regarding the degree to which these different regions interact during information processing. The anatomical connectivity suggests a flow of information between the dorsal and ventral regions; conversely, there are also commissural connections to the contralateral hippocampus. The current study examined the extent to which information from the dorsal hippocampus interacts with processing in the ipsilateral and contralateral ventral hippocampus following the acquisition of a spatial task. METHODS Rats were well-trained on a spatial reference version of the water maze, followed by muscimol inactivation of different hippocampal subregions in a within-animal repeated design. Various combinations of bilateral, ipsilateral, and contralateral infusions were used. RESULTS Combined dorsal and ventral inactivation produced a severe impairment in spatial performance. Inactivation of only the dorsal or ventral regions resulted in intermediate impairment with performance levels falling between controls and combined inactivation. Performance was impaired during contralateral inactivation and was almost equivalent to bilateral dorsal and ventral hippocampus inactivation, while ipsilateral inactivation resulted in little impairment. CONCLUSIONS Taken together, results indicate that for spatial processing, the hippocampus functions as a single integrated structure along the longitudinal axis.
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Affiliation(s)
- Shang Lin (Tommy) Lee
- Behavioral Neuroscience DivisionDepartment of Psychological SciencesUniversity of ConnecticutStorrsCTUSA
| | - Dana Lew
- Behavioral Neuroscience DivisionDepartment of Psychological SciencesUniversity of ConnecticutStorrsCTUSA
| | - Victoria Wickenheisser
- Behavioral Neuroscience DivisionDepartment of Psychological SciencesUniversity of ConnecticutStorrsCTUSA
| | - Etan J. Markus
- Behavioral Neuroscience DivisionDepartment of Psychological SciencesUniversity of ConnecticutStorrsCTUSA
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16
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Dannenberg H, Alexander AS, Robinson JC, Hasselmo ME. The Role of Hierarchical Dynamical Functions in Coding for Episodic Memory and Cognition. J Cogn Neurosci 2019; 31:1271-1289. [PMID: 31251890 DOI: 10.1162/jocn_a_01439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Behavioral research in human verbal memory function led to the initial definition of episodic memory and semantic memory. A complete model of the neural mechanisms of episodic memory must include the capacity to encode and mentally reconstruct everything that humans can recall from their experience. This article proposes new model features necessary to address the complexity of episodic memory encoding and recall in the context of broader cognition and the functional properties of neurons that could contribute to this broader scope of memory. Many episodic memory models represent individual snapshots of the world with a sequence of vectors, but a full model must represent complex functions encoding and retrieving the relations between multiple stimulus features across space and time on multiple hierarchical scales. Episodic memory involves not only the space and time of an agent experiencing events within an episode but also features shown in neurophysiological data such as coding of speed, direction, boundaries, and objects. Episodic memory includes not only a spatio-temporal trajectory of a single agent but also segments of spatio-temporal trajectories for other agents and objects encountered in the environment consistent with data on encoding the position and angle of sensory features of objects and boundaries. We will discuss potential interactions of episodic memory circuits in the hippocampus and entorhinal cortex with distributed neocortical circuits that must represent all features of human cognition.
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17
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Ewell LA, Fischer KB, Leibold C, Leutgeb S, Leutgeb JK. The impact of pathological high-frequency oscillations on hippocampal network activity in rats with chronic epilepsy. eLife 2019; 8:42148. [PMID: 30794155 PMCID: PMC6386518 DOI: 10.7554/elife.42148] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 02/09/2019] [Indexed: 11/29/2022] Open
Abstract
In epilepsy, brain networks generate pathological high-frequency oscillations (pHFOs) during interictal periods. To understand how pHFOs differ from normal oscillations in overlapping frequency bands and potentially perturb hippocampal processing, we performed high-density single unit and local field potential recordings from hippocampi of behaving rats with and without chronic epilepsy. In epileptic animals, we observed two types of co-occurring fast oscillations, which by comparison to control animals we could classify as ‘ripple-like’ or ‘pHFO’. We compared their spectral characteristics, brain state dependence, and cellular participants. Strikingly, pHFO occurred irrespective of brain state, were associated with interictal spikes, engaged distinct subnetworks of principal neurons compared to ripple-like events, increased the sparsity of network activity, and initiated both general and immediate disruptions in spatial information coding. Taken together, our findings suggest that events that result in pHFOs have an immediate impact on memory processes, corroborating the need for proper classification of pHFOs to facilitate therapeutic interventions that selectively target pathological activity.
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Affiliation(s)
- Laura A Ewell
- Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, United States.,Institute of Experimental Epileptology and Cognition Research, University of Bonn Medical Center, Bonn, Germany
| | - Kyle B Fischer
- Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, United States.,Neuroscience Graduate Program, University of California, San Diego, La Jolla, United States
| | - Christian Leibold
- Department Biologie II, Ludwig-Maximilians-Universität München, Martinsried, Germany.,Berstein Center for Computational Neuroscience Munich, Martinried, Germany
| | - Stefan Leutgeb
- Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, United States.,Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, United States
| | - Jill K Leutgeb
- Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, United States
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18
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Moxon KA, Shahlaie K, Girgis F, Saez I, Kennedy J, Gurkoff GG. From adagio to allegretto: The changing tempo of theta frequencies in epilepsy and its relation to interneuron function. Neurobiol Dis 2019; 129:169-181. [PMID: 30798003 DOI: 10.1016/j.nbd.2019.02.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 02/06/2019] [Accepted: 02/20/2019] [Indexed: 12/29/2022] Open
Abstract
Despite decades of research, our understanding of epilepsy, including how seizures are generated and propagate, is incomplete. However, there is growing recognition that epilepsy is more than just the occurrence of seizures, with patients often experiencing comorbid deficits in cognition that are poorly understood. In addition, the available therapies for treatment of epilepsy, from pharmaceutical treatment to surgical resection and seizure prevention devices, often exacerbate deficits in cognitive function. In this review, we discuss the hypothesis that seizure generation and cognitive deficits have a similar pathological source characterized by, but not limited to, deficits in theta oscillations and their influence on interneurons. We present a new framework that describes oscillatory states in epilepsy as alternating between hyper- and hypo-synchrony rather than solely the spontaneous transition to hyper-excitability characterized by the seizures. This framework suggests that as neural oscillations, specifically in the theta range, vary their tempo from a slowed almost adagio tempo during interictal periods to faster, more rhythmic allegretto tempo preictally, they impact the function of interneurons, modulating their ability to control seizures and their role in cognitive processing. This slow wave oscillatory framework may help explain why current therapies that work to reduce hyper-excitability do not completely eliminate seizures and often lead to exacerbated cognitive deficits.
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Affiliation(s)
- Karen A Moxon
- Department of Biomedical Engineering, University of California Davis, Davis, CA 95616, United States of America.
| | - Kiarash Shahlaie
- Department of Neurological Surgery, University of California Davis, Sacramento, CA 95817, United States of America; Center for Neuroscience, University of California Davis, Davis, CA 95618, United States of America
| | - Fady Girgis
- Department of Neurological Surgery, University of California Davis, Sacramento, CA 95817, United States of America
| | - Ignacio Saez
- Department of Neurological Surgery, University of California Davis, Sacramento, CA 95817, United States of America; Center for Neuroscience, University of California Davis, Davis, CA 95618, United States of America
| | - Jeffrey Kennedy
- Department of Neurology, University of California Davis, Sacramento, CA 95817, United States of America
| | - Gene G Gurkoff
- Department of Neurological Surgery, University of California Davis, Sacramento, CA 95817, United States of America; Center for Neuroscience, University of California Davis, Davis, CA 95618, United States of America
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19
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Levcik D, Nekovarova T, Antosova E, Stuchlik A, Klement D. The role of the hippocampus in object discrimination based on visual features. Neurobiol Learn Mem 2018; 155:127-135. [PMID: 29886092 DOI: 10.1016/j.nlm.2018.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 05/09/2018] [Accepted: 06/06/2018] [Indexed: 11/24/2022]
Abstract
The role of rodent hippocampus has been intensively studied in different cognitive tasks. However, its role in discrimination of objects remains controversial due to conflicting findings. We tested whether the number and type of features available for the identification of objects might affect the strategy (hippocampal-independent vs. hippocampal-dependent) that rats adopt to solve object discrimination tasks. We trained rats to discriminate 2D visual objects presented on a computer screen. The objects were defined either by their shape only or by multiple-features (a combination of filling pattern and brightness in addition to the shape). Our data showed that objects displayed as simple geometric shapes are not discriminated by trained rats after their hippocampi had been bilaterally inactivated by the GABAA-agonist muscimol. On the other hand, objects containing a specific combination of non-geometric features in addition to the shape are discriminated even without the hippocampus. Our results suggest that the involvement of the hippocampus in visual object discrimination depends on the abundance of object's features.
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Affiliation(s)
- David Levcik
- Department of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic; Department of Pharmacology, Federal University of Parana, Av. Cel. Francisco Heraclito dos Santos 100, 81531-980 Curitiba, PR, Brazil.
| | - Tereza Nekovarova
- Department of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic; Department of Applied Neurosciences and Brain Imaging, National Institute of Mental Health, Topolova 748, 250 67 Klecany, Czech Republic; Department of Zoology, Faculty of Natural Science, Charles University in Prague, Vinicna 7, 128 00 Prague 2, Czech Republic; Department of Normal, Pathological and Clinical Physiology, 3rd Faculty of Medicine, Charles University, Ke Karlovu 6, 12000 Prague 2, Czech Republic
| | - Eliska Antosova
- Department of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic; Department of Applied Neurosciences and Brain Imaging, National Institute of Mental Health, Topolova 748, 250 67 Klecany, Czech Republic
| | - Ales Stuchlik
- Department of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic
| | - Daniel Klement
- Department of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague 4, Czech Republic
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20
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Hinman JR, Dannenberg H, Alexander AS, Hasselmo ME. Neural mechanisms of navigation involving interactions of cortical and subcortical structures. J Neurophysiol 2018; 119:2007-2029. [PMID: 29442559 DOI: 10.1152/jn.00498.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Animals must perform spatial navigation for a range of different behaviors, including selection of trajectories toward goal locations and foraging for food sources. To serve this function, a number of different brain regions play a role in coding different dimensions of sensory input important for spatial behavior, including the entorhinal cortex, the retrosplenial cortex, the hippocampus, and the medial septum. This article will review data concerning the coding of the spatial aspects of animal behavior, including location of the animal within an environment, the speed of movement, the trajectory of movement, the direction of the head in the environment, and the position of barriers and objects both relative to the animal's head direction (egocentric) and relative to the layout of the environment (allocentric). The mechanisms for coding these important spatial representations are not yet fully understood but could involve mechanisms including integration of self-motion information or coding of location based on the angle of sensory features in the environment. We will review available data and theories about the mechanisms for coding of spatial representations. The computation of different aspects of spatial representation from available sensory input requires complex cortical processing mechanisms for transformation from egocentric to allocentric coordinates that will only be understood through a combination of neurophysiological studies and computational modeling.
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Affiliation(s)
- James R Hinman
- Center for Systems Neuroscience, Boston University , Boston, Massachusetts
| | - Holger Dannenberg
- Center for Systems Neuroscience, Boston University , Boston, Massachusetts
| | - Andrew S Alexander
- Center for Systems Neuroscience, Boston University , Boston, Massachusetts
| | - Michael E Hasselmo
- Center for Systems Neuroscience, Boston University , Boston, Massachusetts
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21
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Korotkova T, Ponomarenko A, Monaghan CK, Poulter SL, Cacucci F, Wills T, Hasselmo ME, Lever C. Reconciling the different faces of hippocampal theta: The role of theta oscillations in cognitive, emotional and innate behaviors. Neurosci Biobehav Rev 2018; 85:65-80. [DOI: 10.1016/j.neubiorev.2017.09.004] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 08/22/2017] [Accepted: 09/02/2017] [Indexed: 12/30/2022]
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22
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Dannenberg H, Young K, Hasselmo M. Modulation of Hippocampal Circuits by Muscarinic and Nicotinic Receptors. Front Neural Circuits 2017; 11:102. [PMID: 29321728 PMCID: PMC5733553 DOI: 10.3389/fncir.2017.00102] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 11/27/2017] [Indexed: 01/02/2023] Open
Abstract
This article provides a review of the effects of activation of muscarinic and nicotinic receptors on the physiological properties of circuits in the hippocampal formation. Previous articles have described detailed computational hypotheses about the role of cholinergic neuromodulation in enhancing the dynamics for encoding in cortical structures and the role of reduced cholinergic modulation in allowing consolidation of previously encoded information. This article will focus on addressing the broad scope of different modulatory effects observed within hippocampal circuits, highlighting the heterogeneity of cholinergic modulation in terms of the physiological effects of activation of muscarinic and nicotinic receptors and the heterogeneity of effects on different subclasses of neurons.
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Affiliation(s)
- Holger Dannenberg
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, MA, United States
| | - Kimberly Young
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, MA, United States
| | - Michael Hasselmo
- Center for Systems Neuroscience, Department of Psychological and Brain Sciences, Boston University, Boston, MA, United States
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23
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Reciprocal changes in noradrenaline and GABA levels in discrete brain regions upon rapid eye movement sleep deprivation in rats. Neurochem Int 2017; 108:190-198. [DOI: 10.1016/j.neuint.2017.03.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 03/19/2017] [Accepted: 03/24/2017] [Indexed: 12/11/2022]
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24
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Jacob PY, Gordillo-Salas M, Facchini J, Poucet B, Save E, Sargolini F. Medial entorhinal cortex and medial septum contribute to self-motion-based linear distance estimation. Brain Struct Funct 2017; 222:2727-2742. [DOI: 10.1007/s00429-017-1368-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 01/11/2017] [Indexed: 11/25/2022]
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25
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First exposure to an alive conspecific activates septal and amygdaloid nuclei in visually-naïve domestic chicks (Gallus gallus). Behav Brain Res 2017; 317:71-81. [DOI: 10.1016/j.bbr.2016.09.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Revised: 09/05/2016] [Accepted: 09/11/2016] [Indexed: 12/29/2022]
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26
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Wang Y, Roth Z, Pastalkova E. Synchronized excitability in a network enables generation of internal neuronal sequences. eLife 2016; 5. [PMID: 27677848 PMCID: PMC5089858 DOI: 10.7554/elife.20697] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 09/13/2016] [Indexed: 02/05/2023] Open
Abstract
Hippocampal place field sequences are supported by sensory cues and network internal mechanisms. In contrast, sharp-wave (SPW) sequences, theta sequences, and episode field sequences are internally generated. The relationship of these sequences to memory is unclear. SPW sequences have been shown to support learning and have been assumed to also support episodic memory. Conversely, we demonstrate these SPW sequences were present in trained rats even after episodic memory was impaired and after other internal sequences - episode field and theta sequences - were eliminated. SPW sequences did not support memory despite continuing to 'replay' all task-related sequences - place- field and episode field sequences. Sequence replay occurred selectively during synchronous increases of population excitability -- SPWs. Similarly, theta sequences depended on the presence of repeated synchronized waves of excitability - theta oscillations. Thus, we suggest that either intermittent or rhythmic synchronized changes of excitability trigger sequential firing of neurons, which in turn supports learning and/or memory.
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Affiliation(s)
- Yingxue Wang
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Zachary Roth
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States.,Department of Mathematics, University of Nebraska-Lincoln, Lincoln, United States
| | - Eva Pastalkova
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
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27
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Stackman RW, Cohen SJ, Lora JC, Rios LM. Temporary inactivation reveals that the CA1 region of the mouse dorsal hippocampus plays an equivalent role in the retrieval of long-term object memory and spatial memory. Neurobiol Learn Mem 2016; 133:118-128. [PMID: 27330015 PMCID: PMC8746693 DOI: 10.1016/j.nlm.2016.06.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 05/10/2016] [Accepted: 06/17/2016] [Indexed: 10/21/2022]
Abstract
Recognition of a previously experienced item or object depends upon the successful retrieval of memory for the object. The neural mechanisms that support object recognition memory in the mammalian brain are not well understood. The rodent hippocampus plays a well-established role in spatial memory, and we previously demonstrated that temporary inactivation of the mouse hippocampus impairs object memory, as assessed with a novel object preference (NOP) test. The present studies were designed to test some remaining issues regarding the contribution of the CA1 sub-region of the mouse dorsal hippocampus to long-term object memory. Specifically, we examined whether the retrieval of spatial memory (as assessed by the Morris water maze; MWM) and object recognition memory are differentially sensitive to inactivation of the CA1 region. The current study used pre-test local microinfusion of muscimol directly into the CA1 region of dorsal hippocampus to temporarily interrupt its function during the respective retrieval phases of both behavioral tasks, in order to compare the contribution of the CA1 to object memory and spatial memory. Histological analyses revealed that local intra-CA1 injection of muscimol diffused within, and not beyond, the CA1 region of dorsal hippocampus. The degree of memory retrieval impairment induced by muscimol was comparable in the two tasks, supporting the view that object memory and spatial memory depend similarly on the CA1 region of rodent hippocampus. Further, we confirmed that the muscimol-induced impairment of CA1 function is temporary. First, mice that exhibited impaired object memory retrieval immediately after intra-CA1 muscimol, subsequently exhibited unimpaired retrieval of object memory when tested 24h later. Secondly, a cohort of mice that exhibited impaired object memory retrieval after intra-CA1 muscimol later acquired spatial memory in the MWM comparable to that of control mice. Together, these results offer further support for the involvement of the CA1 region of mouse hippocampus in object recognition memory, and provide evidence to suggest that the NOP task is as much a test of hippocampal function as the classic MWM test.
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Affiliation(s)
- Robert W Stackman
- Department of Psychology, Florida Atlantic University, John D. MacArthur Campus, Jupiter, FL 33458, USA; Center for Complex Systems & Brain Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA.
| | - Sarah J Cohen
- Center for Complex Systems & Brain Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA
| | - Joan C Lora
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA
| | - Lisa M Rios
- Department of Psychology, Florida Atlantic University, John D. MacArthur Campus, Jupiter, FL 33458, USA; Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA
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28
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Ang ST, Ariffin MZ, Khanna S. The forebrain medial septal region and nociception. Neurobiol Learn Mem 2016; 138:238-251. [PMID: 27444843 DOI: 10.1016/j.nlm.2016.07.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 07/08/2016] [Accepted: 07/17/2016] [Indexed: 10/21/2022]
Abstract
The forebrain medial septum, which is an integral part of the septo-hippocampal network, is implicated in sensorimotor integration, fear and anxiety, and spatial learning and memory. A body of evidence also suggests that the septal region affects experimental pain. Indeed, some explorations in humans have raised the possibility that the region may modulate clinical pain as well. This review explores the evidence that implicates the medial septum in nociception and suggests that non-overlapping circuits in the region facilitate acute nociceptive behaviors and defensive behaviors that reflect affect and cognitive appraisal, especially in relation to persistent nociception. In line with a role in nociception, the region modulates nociceptive responses in the neuraxis, including the hippocampus and the anterior cingulate cortex. The aforementioned forebrain regions have also been implicated in persistent/long-lasting nociception. The review also weighs the effects of the medial septum on nociception vis-à-vis the known roles of the region and emphasizes the fact that the region is a part of network of forebrain structures which have been long associated with reward, cognition and affect-motivation and are now implicated in persistent/long-lasting nociception.
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Affiliation(s)
- Seok Ting Ang
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Mohammed Zacky Ariffin
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Sanjay Khanna
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Neurobiology Program, Life Sciences Institute, National University of Singapore, Singapore.
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29
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Raudies F, Hinman JR, Hasselmo ME. Modelling effects on grid cells of sensory input during self-motion. J Physiol 2016; 594:6513-6526. [PMID: 27094096 DOI: 10.1113/jp270649] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 01/29/2016] [Indexed: 01/07/2023] Open
Abstract
The neural coding of spatial location for memory function may involve grid cells in the medial entorhinal cortex, but the mechanism of generating the spatial responses of grid cells remains unclear. This review describes some current theories and experimental data concerning the role of sensory input in generating the regular spatial firing patterns of grid cells, and changes in grid cell firing fields with movement of environmental barriers. As described here, the influence of visual features on spatial firing could involve either computations of self-motion based on optic flow, or computations of absolute position based on the angle and distance of static visual cues. Due to anatomical selectivity of retinotopic processing, the sensory features on the walls of an environment may have a stronger effect on ventral grid cells that have wider spaced firing fields, whereas the sensory features on the ground plane may influence the firing of dorsal grid cells with narrower spacing between firing fields. These sensory influences could contribute to the potential functional role of grid cells in guiding goal-directed navigation.
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Affiliation(s)
- Florian Raudies
- Center for Systems Neuroscience, Centre for Memory and Brain, Department of Psychological and Brain Sciences and Graduate Program for Neuroscience, Boston University, 2 Cummington Mall, Boston, MA, 02215, USA
| | - James R Hinman
- Center for Systems Neuroscience, Centre for Memory and Brain, Department of Psychological and Brain Sciences and Graduate Program for Neuroscience, Boston University, 2 Cummington Mall, Boston, MA, 02215, USA
| | - Michael E Hasselmo
- Center for Systems Neuroscience, Centre for Memory and Brain, Department of Psychological and Brain Sciences and Graduate Program for Neuroscience, Boston University, 2 Cummington Mall, Boston, MA, 02215, USA
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30
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Synaptic Targets of Medial Septal Projections in the Hippocampus and Extrahippocampal Cortices of the Mouse. J Neurosci 2016; 35:15812-26. [PMID: 26631464 DOI: 10.1523/jneurosci.2639-15.2015] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Temporal coordination of neuronal assemblies among cortical areas is essential for behavioral performance. GABAergic projections from the medial septum and diagonal band complex exclusively innervate GABAergic interneurons in the rat hippocampus, contributing to the coordination of neuronal activity, including the generation of theta oscillations. Much less is known about the synaptic target neurons outside the hippocampus. To reveal the contribution of synaptic circuits involving the medial septum of mice, we have identified postsynaptic cortical neurons in wild-type and parvalbumin-Cre knock-in mice. Anterograde axonal tracing from the septum revealed extensive innervation of the hippocampus as well as the subiculum, presubiculum, parasubiculum, the medial and lateral entorhinal cortices, and the retrosplenial cortex. In all examined cortical regions, many septal GABAergic boutons were in close apposition to somata or dendrites immunopositive for interneuron cell-type molecular markers, such as parvalbumin, calbindin, calretinin, N-terminal EF-hand calcium-binding protein 1, cholecystokinin, reelin, or a combination of these molecules. Electron microscopic observations revealed septal boutons forming axosomatic or axodendritic type II synapses. In the CA1 region of hippocampus, septal GABAergic projections exclusively targeted interneurons. In the retrosplenial cortex, 93% of identified postsynaptic targets belonged to interneurons and the rest to pyramidal cells. These results suggest that the GABAergic innervation from the medial septum and diagonal band complex contributes to temporal coordination of neuronal activity via several types of cortical GABAergic interneurons in both hippocampal and extrahippocampal cortices. Oscillatory septal neuronal firing at delta, theta, and gamma frequencies may phase interneuron activity.
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Synergy of direct and indirect cholinergic septo-hippocampal pathways coordinates firing in hippocampal networks. J Neurosci 2015; 35:8394-410. [PMID: 26041909 DOI: 10.1523/jneurosci.4460-14.2015] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The medial septum/diagonal band of Broca complex (MSDB) is a key structure that modulates hippocampal rhythmogenesis. Cholinergic neurons of the MSDB play a central role in generating and pacing theta-band oscillations in the hippocampal formation during exploration, novelty detection, and memory encoding. How precisely cholinergic neurons affect hippocampal network dynamics in vivo, however, has remained elusive. In this study, we show that stimulation of cholinergic MSDB neurons in urethane-anesthetized mice acts on hippocampal networks via two distinct pathways. A direct septo-hippocampal cholinergic projection causes increased firing of hippocampal inhibitory interneurons with concomitantly decreased firing of principal cells. In addition, cholinergic neurons recruit noncholinergic neurons within the MSDB. This indirect pathway is required for hippocampal theta synchronization. Activation of both pathways causes a reduction in pyramidal neuron firing and a more precise coupling to the theta oscillatory phase. These two anatomically and functionally distinct pathways are likely relevant for cholinergic control of encoding versus retrieval modes in the hippocampus.
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Hasselmo ME. If I had a million neurons: Potential tests of cortico-hippocampal theories. PROGRESS IN BRAIN RESEARCH 2015; 219:1-19. [PMID: 26072231 DOI: 10.1016/bs.pbr.2015.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Considerable excitement surrounds new initiatives to develop techniques for simultaneous recording of large populations of neurons in cortical structures. This chapter focuses on the potential value of large-scale simultaneous recording for advancing research on current issues in the function of cortical circuits, including the interaction of the hippocampus with cortical and subcortical structures. The review describes specific research questions that could be answered using large-scale population recording, including questions about the circuit dynamics underlying coding of dimensions of space and time for episodic memory, the role of GABAergic and cholinergic innervation from the medial septum, the functional role of spatial representations coded by grid cells, boundary cells, head direction cells, and place cells, and the fact that many models require cells coding movement direction.
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Affiliation(s)
- Michael E Hasselmo
- Department of Psychological and Brain Sciences, Center for Memory and Brain, Center for Systems Neuroscience, Graduate Program for Neuroscience, Boston University, Boston, MA, USA.
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Hasselmo ME, Stern CE. Current questions on space and time encoding. Hippocampus 2015; 25:744-52. [PMID: 25786389 DOI: 10.1002/hipo.22454] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2015] [Indexed: 01/18/2023]
Abstract
The Nobel Prize in Physiology or Medicine 2014 celebrated the groundbreaking findings on place cells and grid cells by John O'Keefe and May-Britt Moser and Edvard Moser. These findings provided an essential foothold for understanding the cognitive encoding of space and time in episodic memory function. This foothold provides a closer view of a broad new world of important research questions raised by the phenomena of place cells and grid cells. These questions concern the mechanisms of generation of place and grid cell firing, including sensory influences, circuit dynamics and intrinsic properties. Similar questions concern the generation of time cells. In addition, questions concern the functional role of place cells, grid cells and time cells in mediating goal-directed behavior and episodic memory function.
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Affiliation(s)
- Michael E Hasselmo
- Center for Systems Neuroscience, Center for Memory and Brain, Department of Psychological and Brain Sciences and Graduate Program for Neuroscience, Boston University, Boston, Massachusetts
| | - Chantal E Stern
- Center for Systems Neuroscience, Center for Memory and Brain, Department of Psychological and Brain Sciences and Graduate Program for Neuroscience, Boston University, Boston, Massachusetts
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Wang Y, Romani S, Lustig B, Leonardo A, Pastalkova E. Theta sequences are essential for internally generated hippocampal firing fields. Nat Neurosci 2014; 18:282-8. [PMID: 25531571 DOI: 10.1038/nn.3904] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 11/24/2014] [Indexed: 11/09/2022]
Abstract
Sensory cue inputs and memory-related internal brain activities govern the firing of hippocampal neurons, but which specific firing patterns are induced by either of the two processes remains unclear. We found that sensory cues guided the firing of neurons in rats on a timescale of seconds and supported the formation of spatial firing fields. Independently of the sensory inputs, the memory-related network activity coordinated the firing of neurons not only on a second-long timescale, but also on a millisecond-long timescale, and was dependent on medial septum inputs. We propose a network mechanism that might coordinate this internally generated firing. Overall, we suggest that two independent mechanisms support the formation of spatial firing fields in hippocampus, but only the internally organized system supports short-timescale sequential firing and episodic memory.
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Affiliation(s)
| | - Sandro Romani
- 1] Janelia Research Campus, Ashburn, Virginia, USA. [2] Center for Theoretical Neuroscience, Columbia University, New York, New York, USA
| | - Brian Lustig
- 1] Janelia Research Campus, Ashburn, Virginia, USA. [2] University of Chicago, Neuroscience Graduate Program, Chicago, Illinois, USA
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Sandler RA, Song D, Hampson RE, Deadwyler SA, Berger TW, Marmarelis VZ. Model-based asessment of an in-vivo predictive relationship from CA1 to CA3 in the rodent hippocampus. J Comput Neurosci 2014; 38:89-103. [PMID: 25260381 DOI: 10.1007/s10827-014-0530-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 09/02/2014] [Accepted: 09/05/2014] [Indexed: 01/02/2023]
Abstract
Although an anatomical connection from CA1 to CA3 via the Entorhinal Cortex (EC) and through backprojecting interneurons has long been known it exist, it has never been examined quantitatively on the single neuron level, in the in-vivo nonpatholgical, nonperturbed brain. Here, single spike activity was recorded using a multi-electrode array from the CA3 and CA1 areas of the rodent hippocampus (N = 7) during a behavioral task. The predictive power from CA3→CA1 and CA1→CA3 was examined by constructing Multivariate Autoregressive (MVAR) models from recorded neurons in both directions. All nonsignificant inputs and models were identified and removed by means of Monte Carlo simulation methods. It was found that 121/166 (73 %) CA3→CA1 models and 96/145 (66 %) CA1→CA3 models had significant predictive power, thus confirming a predictive 'Granger' causal relationship from CA1 to CA3. This relationship is thought to be caused by a combination of truly causal connections such as the CA1→EC→CA3 pathway and common inputs such as those from the Septum. All MVAR models were then examined in the frequency domain and it was found that CA3 kernels had significantly more power in the theta and beta range than those of CA1, confirming CA3's role as an endogenous hippocampal pacemaker.
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Affiliation(s)
- Roman A Sandler
- Department of Biomedical Engineering, University of Southern California, DRB 367, 1042 Downey Way Los Angeles, Los Angeles, CA, 90089, USA,
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Cohen SJ, Stackman RW. Assessing rodent hippocampal involvement in the novel object recognition task. A review. Behav Brain Res 2014; 285:105-17. [PMID: 25169255 DOI: 10.1016/j.bbr.2014.08.002] [Citation(s) in RCA: 379] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Revised: 07/18/2014] [Accepted: 08/01/2014] [Indexed: 12/15/2022]
Abstract
The novel object recognition (NOR) task has emerged as a popular method for testing the neurobiology of nonspatial memory in rodents. This task exploits the natural tendency of rodents to explore novel items and depending on the amount of time that rodents spend exploring the presented objects, inferences about memory can be established. Despite its wide use, the underlying neural circuitry and mechanisms supporting NOR have not been clearly defined. In particular, considerable debate has focused on whether the hippocampus plays a significant role in the object memory that is encoded, consolidated and then retrieved during discrete stages of the NOR task. Here we analyzed the results of all published reports in which the role of the rodent hippocampus in object memory was inferred from performance in the task with restricted parameters. We note that the remarkable variability in NOR methods across studies complicates the ability to draw meaningful conclusions from the work. Focusing on 12 reports in which a minimum criterion of sample session object exploration was imposed, we find that temporary or permanent lesion of the hippocampus consistently disrupts object memory when a delay of 10 min or greater is imposed between the sample and test sessions. We discuss the significance of a delay-dependent role of the hippocampus in NOR within the framework of the medial temporal lobe. We assert that standardization of the NOR protocol is essential for obtaining reliable data that can then be compared across studies to build consensus as to the specific contribution of the rodent hippocampus to object memory.
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Affiliation(s)
- Sarah J Cohen
- Center for Complex Systems & Brain Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA.
| | - Robert W Stackman
- Center for Complex Systems & Brain Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA; Department of Psychology, Charles E. Schmidt College of Science, Florida Atlantic University, John D. MacArthur Campus, 5353 Parkside Drive, Jupiter, FL 33458, USA.
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Medial septum-diagonal band of Broca (MSDB) GABAergic regulation of hippocampal acetylcholine efflux is dependent on cognitive demands. J Neurosci 2014; 34:506-14. [PMID: 24403150 DOI: 10.1523/jneurosci.2352-13.2014] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The septohippocampal pathway contains cholinergic, GABAergic, and glutamatergic projections and has an established role in learning, memory, and hippocampal theta rhythm. Both GABAergic and cholinergic neurons in the medial septum-diagonal band of Broca (MSDB) have been associated with spatial memory, but the relationship between the two neuronal populations is not fully understood. The present study investigated the effect of selective GABAergic MSDB lesions on hippocampal acetylcholine (ACh) efflux and spatial memory during tasks that varied in memory demand. Male Sprague Dawley rats were given GABAergic lesions of the MSDB using GAT1-saporin (GAT1-SAP) and examined on spontaneous exploration (Experiment 1) and non-matching to position without (NMTP; Experiment 2) and with a delay (DNMTP; Experiment 3), while concurrently using in vivo microdialysis to measure hippocampal ACh efflux. Intraseptal GAT1-SAP treatment did not alter baseline or behaviorally stimulated hippocampal ACh efflux or maze exploration (Experiment 1). Moreover, GAT1-SAP did not alter evoked hippocampal ACh efflux related to NMTP nor did it impair working memory in NMTP (Experiment 2). In contrast, both ACh efflux and performance in DNMTP were impaired by intraseptal GAT1-SAP. Thus, GABAergic MSDB neurons are important for spatial working memory and modulate hippocampal ACh efflux under conditions of high memory load. The relationship between the septohippocampal cholinergic and GABAergic systems and working memory will be discussed.
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Raccuglia D, Mueller U. Focal uncaging of GABA reveals a temporally defined role for GABAergic inhibition during appetitive associative olfactory conditioning in honeybees. Learn Mem 2013; 20:410-6. [PMID: 23860600 DOI: 10.1101/lm.030205.112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Throughout the animal kingdom, the inhibitory neurotransmitter γ-aminobutyric acid (GABA) is a key modulator of physiological processes including learning. With respect to associative learning, the exact time in which GABA interferes with the molecular events of learning has not yet been clearly defined. To address this issue, we used two different approaches to activate GABA receptors during appetitive olfactory conditioning in the honeybee. Injection of GABA-A receptor agonist muscimol 20 min before but not 20 min after associative conditioning affects memory performance. These memory deficits were attenuated by additional training sessions. Muscimol has no effect on sensory perception, odor generalization, and nonassociative learning, indicating a specific role of GABA during associative conditioning. We used photolytic uncaging of GABA to identify the GABA-sensitive time window during the short pairing of the conditioned stimulus (CS) and the unconditioned stimulus (US) that lasts only seconds. Either uncaging of GABA in the antennal lobes or the mushroom bodies during the CS presentation of the CS-US pairing impairs memory formation, while uncaging GABA during the US phase has no effect on memory. Uncaging GABA during the CS presentation in memory retrieval also has no effect. Thus, in honeybee appetitive olfactory learning GABA specifically interferes with the integration of CS and US during associative conditioning and exerts a modulatory role in memory formation depending on the training strength.
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Affiliation(s)
- Davide Raccuglia
- Department 8.3 Biosciences Zoology/Physiology-Neurobiology, ZHMB Center of Human and Molecular Biology, Faculty 8-Natural Science and Technology III, Saarland University, D-66041 Saarbrücken, Germany
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Hasselmo ME, Stern CE. Theta rhythm and the encoding and retrieval of space and time. Neuroimage 2013; 85 Pt 2:656-66. [PMID: 23774394 DOI: 10.1016/j.neuroimage.2013.06.022] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 05/28/2013] [Accepted: 06/04/2013] [Indexed: 11/25/2022] Open
Abstract
Physiological data demonstrates theta frequency oscillations associated with memory function and spatial behavior. Modeling and data from animals provide a perspective on the functional role of theta rhythm, including correlations with behavioral performance and coding by timing of spikes relative to phase of oscillations. Data supports a theorized role of theta rhythm in setting the dynamics for encoding and retrieval within cortical circuits. Recent data also supports models showing how network and cellular theta rhythmicity allows neurons in the entorhinal cortex and hippocampus to code time and space as a possible substrate for encoding events in episodic memory. Here we discuss these models and relate them to current physiological and behavioral data.
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Affiliation(s)
- Michael E Hasselmo
- Center for Memory and Brain, Department of Psychology and Graduate Program for Neuroscience, Boston University, 2 Cummington Mall, Boston, MA, 02215, USA.
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40
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Segregation of cortical head direction cell assemblies on alternating θ cycles. Nat Neurosci 2013; 16:739-48. [PMID: 23603709 PMCID: PMC3703458 DOI: 10.1038/nn.3383] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 03/19/2013] [Indexed: 12/20/2022]
Abstract
High-level cortical systems for spatial navigation, including entorhinal grid cells, critically depend on input from the head direction system. We examined spiking rhythms and modes of synchrony between neurons participating in head direction networks for evidence of internal processing, independent of direct sensory drive, which may be important for grid cell function. We demonstrate that head direction networks of rats are segregated into at least two populations of neurons firing on alternate theta cycles (theta cycle skipping) with fixed synchronous or anti-synchronous relationships. Pairs of anti-synchronous theta cycle skipping neurons exhibited larger differences in head direction tuning with a minimum difference of 40 degrees of head direction. Septal inactivation preserved the head direction signal but eliminated theta cycle skipping of head direction cells and grid cell spatial periodicity. We propose that internal mechanisms underlying cycle skipping in head direction networks may be critical for downstream spatial computation by grid cells.
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Gould KL, Gilbertson KE, Hrvol AJ, Nelson JC, Seyfer AL, Brantner RM, Kamil AC. Differences in relative hippocampus volume and number of hippocampus neurons among five corvid species. BRAIN, BEHAVIOR AND EVOLUTION 2013; 81:56-70. [PMID: 23364270 DOI: 10.1159/000345560] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 05/02/2012] [Indexed: 11/19/2022]
Abstract
The relative size of the avian hippocampus (Hp) has been shown to be related to spatial memory and food storing in two avian families, the parids and corvids. Basil et al. [Brain Behav Evol 1996;47:156-164] examined North American food-storing birds in the corvid family and found that Clark's nutcrackers had a larger relative Hp than pinyon jays and Western scrub jays. These results correlated with the nutcracker's better performance on most spatial memory tasks and their strong reliance on stored food in the wild. However, Pravosudov and de Kort [Brain Behav Evol 2006;67:1-9] raised questions about the methodology used in the 1996 study, specifically the use of paraffin as an embedding material and recalculation for shrinkage. Therefore, we measured relative Hp volume using gelatin as the embedding material in four North American species of food-storing corvids (Clark's nutcrackers, pinyon jays, Western scrub jays and blue jays) and one Eurasian corvid that stores little to no food (azure-winged magpies). Although there was a significant overall effect of species on relative Hp volume among the five species, subsequent tests found only one pairwise difference, blue jays having a larger Hp than the azure-winged magpies. We also examined the relative size of the septum in the five species. Although Shiflett et al. [J Neurobiol 2002;51:215-222] found a difference in relative septum volume amongst three species of parids that correlated with storing food, we did not find significant differences amongst the five species in relative septum. Finally, we calculated the number of neurons in the Hp relative to body mass in the five species and found statistically significant differences, some of which are in accord with the adaptive specialization hypothesis and some are not.
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Affiliation(s)
- Kristy L Gould
- Department of Psychology, Luther College, Decorah, IA 52101, USA.
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Talishinsky A, Rosen GD. Systems genetics of the lateral septal nucleus in mouse: heritability, genetic control, and covariation with behavioral and morphological traits. PLoS One 2012; 7:e44236. [PMID: 22952935 PMCID: PMC3432065 DOI: 10.1371/journal.pone.0044236] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 07/30/2012] [Indexed: 11/19/2022] Open
Abstract
The lateral septum has strong efferent projections to hypothalamic and midbrain regions, and has been associated with modulation of social behavior, anxiety, fear conditioning, memory-related behaviors, and the mesolimbic reward pathways. Understanding natural variation of lateral septal anatomy and function, as well as its genetic modulation, may provide important insights into individual differences in these evolutionarily important functions. Here we address these issues by using efficient and unbiased stereological probes to estimate the volume of the lateral septum in the BXD line of recombinant inbred mice. Lateral septum volume is a highly variable trait, with a 2.5-fold difference among animals. We find that this trait covaries with a number of behavioral and physiological phenotypes, many of which have already been associated with behaviors modulated by the lateral septum, such as spatial learning, anxiety, and reward-seeking. Heritability of lateral septal volume is moderate (h(2) = 0.52), and much of the heritable variation is caused by a locus on the distal portion of chromosome (Chr) 1. Composite interval analysis identified a secondary interval on Chr 2 that works additively with the Chr 1 locus to increase lateral septum volume. Using bioinformatic resources, we identified plausible candidate genes in both intervals that may influence the volume of this key nucleus, as well as associated behaviors.
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Affiliation(s)
- Alexander Talishinsky
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
| | - Glenn D. Rosen
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America
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Hasselmo ME, Brandon MP. A model combining oscillations and attractor dynamics for generation of grid cell firing. Front Neural Circuits 2012; 6:30. [PMID: 22654735 PMCID: PMC3361022 DOI: 10.3389/fncir.2012.00030] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Accepted: 05/04/2012] [Indexed: 11/24/2022] Open
Abstract
Different models have been able to account for different features of the data on grid cell firing properties, including the relationship of grid cells to cellular properties and network oscillations. This paper describes a model that combines elements of two major classes of models of grid cells: models using interactions of oscillations and models using attractor dynamics. This model includes a population of units with oscillatory input representing input from the medial septum. These units are termed heading angle cells because their connectivity depends upon heading angle in the environment as well as the spatial phase coded by the cell. These cells project to a population of grid cells. The sum of the heading angle input results in standing waves of circularly symmetric input to the grid cell population. Feedback from the grid cell population increases the activity of subsets of the heading angle cells, resulting in the network settling into activity patterns that resemble the patterns of firing fields in a population of grid cells. The properties of heading angle cells firing as conjunctive grid-by-head-direction cells can shift the grid cell firing according to movement velocity. The pattern of interaction of oscillations requires use of separate populations that fire on alternate cycles of the net theta rhythmic input to grid cells.
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Affiliation(s)
- Michael E Hasselmo
- Graduate Program for Neuroscience, Department of Psychology, Center for Memory and Brain, Boston University Boston, MA, USA
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Hippocampal extracellular signal-regulated kinase signaling has a role in passive avoidance memory retrieval induced by GABAA Receptor modulation in mice. Neuropsychopharmacology 2012; 37:1234-44. [PMID: 22169949 PMCID: PMC3306885 DOI: 10.1038/npp.2011.311] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Available evidence strongly suggests that the γ-aminobutyric acid type A (GABA(A)) receptor has a crucial role in memory retrieval. However, the signaling mechanisms underlying the role of GABA(A) receptor modulation in memory retrieval are unclear. We conducted one-trial passive avoidance task with pre-retention trial drug administration in the hippocampus to test the effects of GABA(A) receptor modulation on memory retrieval. We further tested the co-involvement of signaling molecules: extracellular signal-regulated kinase (ERK), Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), and cAMP responsive element-binding protein (CREB). First, we observed that the phosphorylation of hippocampal ERK was required for memory retrieval during the task. Accordingly, to investigate whether GABA(A) receptor activation or inhibition induces ERK phosphorylation during memory retrieval, drugs that target the GABA(A) receptor were administered into the hippocampus before the retention trial. Muscimol, a GABA(A) receptor agonist, and diazepam, an agonist to benzodiazepine-binding site of GABA(A) receptor, blocked retention trial-induced ERK phosphorylation and impaired memory retrieval. Furthermore, co-treatment with sub-effective dose of U0126, a mitogen-activated protein kinase inhibitor, blocked the upregulation of ERK phosphorylation and impaired memory retrieval, and bicuculline methiodide (BMI), a GABA(A) receptor antagonist, increased ERK phosphorylation induced by the retention trial and facilitated memory retrieval. Finally, the effects of BMI were blocked by the co-application of a sub-effective dose of U0126. These results suggest that GABA(A) receptor-mediated memory retrieval is closely related to ERK activity.
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Brandon MP, Bogaard AR, Libby CP, Connerney MA, Gupta K, Hasselmo ME. Reduction of theta rhythm dissociates grid cell spatial periodicity from directional tuning. Science 2011; 332:595-9. [PMID: 21527714 PMCID: PMC3252766 DOI: 10.1126/science.1201652] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Grid cells recorded in the medial entorhinal cortex of freely moving rats exhibit firing at regular spatial locations and temporal modulation with theta rhythm oscillations (4 to 11 hertz). We analyzed grid cell spatial coding during reduction of network theta rhythm oscillations caused by medial septum (MS) inactivation with muscimol. During MS inactivation, grid cells lost their spatial periodicity, whereas head-direction cells maintained their selectivity. Conjunctive grid-by-head-direction cells lost grid cell spatial periodicity but retained head-direction specificity. All cells showed reduced rhythmicity in autocorrelations and cross-correlations. This supports the hypothesis that spatial coding by grid cells requires theta oscillations, and dissociates the mechanisms underlying the generation of entorhinal grid cell periodicity and head-direction selectivity.
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Affiliation(s)
- Mark P. Brandon
- Center for Memory and Brain, Department of Psychology, Graduate Program in Neuroscience, Boston University, Boston Massachusetts, 02215, U.S.A
| | - Andrew R. Bogaard
- Center for Memory and Brain, Department of Psychology, Graduate Program in Neuroscience, Boston University, Boston Massachusetts, 02215, U.S.A
| | - Christopher P. Libby
- Center for Memory and Brain, Department of Psychology, Graduate Program in Neuroscience, Boston University, Boston Massachusetts, 02215, U.S.A
| | - Michael A. Connerney
- Center for Memory and Brain, Department of Psychology, Graduate Program in Neuroscience, Boston University, Boston Massachusetts, 02215, U.S.A
| | - Kishan Gupta
- Center for Memory and Brain, Department of Psychology, Graduate Program in Neuroscience, Boston University, Boston Massachusetts, 02215, U.S.A
| | - Michael E. Hasselmo
- Center for Memory and Brain, Department of Psychology, Graduate Program in Neuroscience, Boston University, Boston Massachusetts, 02215, U.S.A
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Villette V, Poindessous-Jazat F, Simon A, Léna C, Roullot E, Bellessort B, Epelbaum J, Dutar P, Stéphan A. Decreased rhythmic GABAergic septal activity and memory-associated theta oscillations after hippocampal amyloid-beta pathology in the rat. J Neurosci 2010; 30:10991-1003. [PMID: 20720106 PMCID: PMC6633464 DOI: 10.1523/jneurosci.6284-09.2010] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Revised: 05/26/2010] [Accepted: 06/22/2010] [Indexed: 01/22/2023] Open
Abstract
The memory deficits associated with Alzheimer's disease result to a great extent from hippocampal network dysfunction. The coordination of this network relies on theta (symbol) oscillations generated in the medial septum. Here, we investigated in rats the impact of hippocampal amyloid beta (Abeta) injections on the physiological and cognitive functions that depend on the septohippocampal system. Hippocampal Abeta injections progressively impaired behavioral performances, the associated hippocampal theta power, and theta frequency response in a visuospatial recognition test. These alterations were associated with a specific reduction in the firing of the identified rhythmic bursting GABAergic neurons responsible for the propagation of the theta rhythm to the hippocampus, but without loss of medial septal neurons. Such results indicate that hippocampal Abeta treatment leads to a specific functional depression of inhibitory projection neurons of the medial septum, resulting in the functional impairment of the temporal network.
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Affiliation(s)
- Vincent Villette
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
| | - Frédérique Poindessous-Jazat
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
| | - Axelle Simon
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
| | - Clément Léna
- Laboratoire de Neurobiologie, UMR 8544, Ecole Normale Supérieure, 75005 Paris, France, and
| | - Elodie Roullot
- Ecole Spéciale de Mécanique et d'Electricité-Sudria, Pôle de Recherche en Imagerie Appliquée à la Médecine, 94200 Ivry sur Seine, France
| | - Brice Bellessort
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
| | - Jacques Epelbaum
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
| | - Patrick Dutar
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
| | - Aline Stéphan
- Inserm Centre de Psychiatrie et Neurosciences, Unité Mixte de Recherche (UMR) 894, 75014 Paris, France
- Université Paris Descartes, Faculté de Médecine, 75005 Paris, France
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Bidirectional changes to hippocampal theta-gamma comodulation predict memory for recent spatial episodes. Proc Natl Acad Sci U S A 2010; 107:7054-9. [PMID: 20351262 DOI: 10.1073/pnas.0911184107] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Episodic memory requires the hippocampus, which is thought to bind cortical inputs into conjunctive codes. Local field potentials (LFPs) reflect dendritic and synaptic oscillations whose temporal structure may coordinate cellular mechanisms of plasticity and memory. We now report that single-trial spatial memory performance in rats was predicted by the power comodulation of theta (4-10 Hz) and low gamma (30-50 Hz) rhythms in the hippocampus. Theta-gamma comodulation (TGC) was prominent during successful memory retrieval but was weak when memory failed or was unavailable during spatial exploration in sample trials. Muscimol infusion into medial septum reduced the probability of TGC and successful memory retrieval. In contrast, patterned electrical stimulation of the fimbria-fornix increased TGC in amnestic animals and partially rescued memory performance in the water maze. The results suggest that TGC accompanies memory retrieval in the hippocampus and that patterned brain stimulation may inform therapeutic strategies for cognitive disorders.
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Krebs-Kraft DL, Wheeler MG, Parent MB. The memory-impairing effects of septal GABA receptor activation involve GABAergic septo-hippocampal projection neurons. Learn Mem 2007; 14:833-41. [PMID: 18086826 DOI: 10.1101/lm.809407] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Septal infusions of the gamma-aminobutyric acid (GABA)(A) agonist muscimol impair memory, and the effect likely involves the hippocampus. GABA(A) receptors are present on the perikarya of cholinergic and GABAergic septo-hippocampal (SH) projections. The current experiments determined whether GABAergic SH projections are involved in the memory-impairing effects of septal GABA(A) receptor activation. Experiment 1 tested whether combining septal co-infusions of subeffective doses of muscimol with scopolamine, a drug that selectively influences GABA SH projections, would produce memory deficits. Experiment 2 tested whether hippocampal infusions of a GABA(A) receptor antagonist would block the effects of septal muscimol infusions. Fifteen minutes prior to assessing spontaneous alternation (SA) or training in a multiple trial inhibitory avoidance (CMIA) task, male Sprague-Dawley rats were given septal infusions of vehicle, muscimol, scopolamine, or co-infusions of muscimol with scopolamine, or septal infusions of vehicle or muscimol combined with hippocampal infusions of vehicle or bicuculline. Septal co-infusions of muscimol with scopolamine significantly impaired SA and CMIA. Hippocampal bicuculline infusions blocked deficits produced by septal muscimol infusions in SA and attenuated deficits produced in CMIA. Combined, these findings suggest that GABAergic SH projections are involved in the memory-impairing effects of septal GABA receptor activation.
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Yamamoto Y, Mikami A, Fujii Y, Kamei C. Effect of histamine on muscimol-induced working memory deficits in radial maze performance. J Pharmacol Sci 2007; 104:252-7. [PMID: 17598950 DOI: 10.1254/jphs.fp0061472] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
We investigated the participation of gamma-aminobutyric acid (GABA) neurons of the medial septal area in eight-arm radial maze performance in rats. The intra-septal injection of muscimol, a GABA(A) agonist, caused an increase in total error and working memory error. On the other hand, no significant effect was observed with reference memory error. Donepezil and tacrine (cholinesterase inhibitors) antagonized the muscimol-induced spatial memory deficits. Histidine (1500 mg/kg, i.p.) also improved the total error and working memory error induced by muscimol. At this dose, histidine caused a significant increase in the histamine content of the cortex, hippocampus, and hypothalamus in rats. In addition, the intra-hippocampal injection of histamine also antagonized muscimol-induced spatial memory deficits. The practical conclusion is that the GABA(A) receptor of the medial septal area plays an important role in working memory, and also, the disturbance of working memory induced by muscimol is mediated not only by cholinergic but also by histaminergic systems in the spatial memory of rats.
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Affiliation(s)
- Yasuko Yamamoto
- Department of Medicinal Pharmacology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8530, Japan
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50
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McNay EC, Canal CE, Sherwin RS, Gold PE. Modulation of memory with septal injections of morphine and glucose: effects on extracellular glucose levels in the hippocampus. Physiol Behav 2005; 87:298-303. [PMID: 16343563 DOI: 10.1016/j.physbeh.2005.10.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Revised: 09/19/2005] [Accepted: 10/19/2005] [Indexed: 11/26/2022]
Abstract
The concentration of glucose in the extracellular fluid (ECF) of the hippocampus decreases substantially during memory testing on a hippocampus-dependent memory task. Administration of exogenous glucose, which enhances task performance, prevents this decrease, suggesting a relationship between hippocampal glucose availability and memory performance. In the present experiment, spontaneous alternation performance and task-related changes in hippocampal ECF glucose were assessed in rats after intraseptal administration of morphine, which impairs memory on a spontaneous alternation task, and after co-administration of intraseptal glucose, which attenuates that impairment. Consistent with previous findings, spontaneous alternation testing resulted in a decrease in hippocampal ECF glucose levels in control rats. However, rats that received intraseptal morphine prior to testing showed memory impairments and an absence of the task-related decrease in hippocampal ECF glucose levels. Intraseptal co-administration of glucose with morphine attenuated the memory impairment, and ECF glucose levels in the hippocampus decreased in a manner comparable to that seen in control rats. These data suggest that fluctuations in hippocampal ECF glucose levels may be a marker of mnemonic processing and support the view that decreases in extracellular glucose during memory testing reflect increased glucose demand during memory processing.
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Affiliation(s)
- Ewan C McNay
- Section of Endocrinology, Yale University School of Medicine, USA
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