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Jedrasiak-Cape I, Rybicki-Kler C, Brooks I, Ghosh M, Brennan EK, Kailasa S, Ekins TG, Rupp A, Ahmed OJ. Cell-type-specific cholinergic control of granular retrosplenial cortex with implications for angular velocity coding across brain states. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.04.597341. [PMID: 38895393 PMCID: PMC11185600 DOI: 10.1101/2024.06.04.597341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Cholinergic receptor activation enables the persistent firing of cortical pyramidal neurons, providing a key cellular basis for theories of spatial navigation involving working memory, path integration, and head direction encoding. The granular retrosplenial cortex (RSG) is important for spatially-guided behaviors, but how acetylcholine impacts RSG neurons is unknown. Here, we show that a transcriptomically, morphologically, and biophysically distinct RSG cell-type - the low-rheobase (LR) neuron - has a very distinct expression profile of cholinergic muscarinic receptors compared to all other neighboring excitatory neuronal subtypes. LR neurons do not fire persistently in response to cholinergic agonists, in stark contrast to all other principal neuronal subtypes examined within the RSG and across midline cortex. This lack of persistence allows LR neuron models to rapidly compute angular head velocity (AHV), independent of cholinergic changes seen during navigation. Thus, LR neurons can consistently compute AHV across brain states, highlighting the specialized RSG neural codes supporting navigation.
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Affiliation(s)
| | - Chloe Rybicki-Kler
- Dept. of Psychology, University of Michigan, Ann Arbor, MI 48109
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109
| | - Isla Brooks
- Dept. of Psychology, University of Michigan, Ann Arbor, MI 48109
| | - Megha Ghosh
- Dept. of Psychology, University of Michigan, Ann Arbor, MI 48109
| | - Ellen K.W. Brennan
- Dept. of Psychology, University of Michigan, Ann Arbor, MI 48109
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109
| | - Sameer Kailasa
- Dept. of Mathematics, University of Michigan, Ann Arbor, MI 48109
| | - Tyler G. Ekins
- Dept. of Psychology, University of Michigan, Ann Arbor, MI 48109
| | - Alan Rupp
- Dept. of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Omar J. Ahmed
- Dept. of Psychology, University of Michigan, Ann Arbor, MI 48109
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI 48109
- Dept. of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
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2
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Dillingham CM, Wilson JJ, Vann SD. Electrophysiological Properties of the Medial Mammillary Bodies across the Sleep-Wake Cycle. eNeuro 2024; 11:ENEURO.0447-23.2024. [PMID: 38621991 PMCID: PMC11055652 DOI: 10.1523/eneuro.0447-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 03/19/2024] [Accepted: 03/25/2024] [Indexed: 04/17/2024] Open
Abstract
The medial mammillary bodies (MBs) play an important role in the formation of spatial memories; their dense inputs from hippocampal and brainstem regions makes them well placed to integrate movement-related and spatial information, which is then extended to the anterior thalamic nuclei and beyond to the cortex. While the anatomical connectivity of the medial MBs has been well studied, much less is known about their physiological properties, particularly in freely moving animals. We therefore carried out a comprehensive characterization of medial MB electrophysiology across arousal states by concurrently recording from the medial MB and the CA1 field of the hippocampus in male rats. In agreement with previous studies, we found medial MB neurons to have firing rates modulated by running speed and angular head velocity, as well as theta-entrained firing. We extended the characterization of MB neuron electrophysiology in three key ways: (1) we identified a subset of neurons (25%) that exhibit dominant bursting activity; (2) we showed that ∼30% of theta-entrained neurons exhibit robust theta cycle skipping, a firing characteristic that implicates them in a network for prospective coding of position; and (3) a considerable proportion of medial MB units showed sharp-wave ripple (SWR) responsive firing (∼37%). The functional heterogeneity of MB electrophysiology reinforces their role as an integrative node for mnemonic processing and identifies potential roles for the MBs in memory consolidation through propagation of SWR-responsive activity to the anterior thalamus and prospective coding in the form of theta cycle skipping.
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Affiliation(s)
- Christopher M Dillingham
- School of Psychology, Cardiff University, Cardiff CF10 3AT, United Kingdom
- Neuroscience and Mental Health Innovation Institute, Cardiff CF24 4HQ, United Kingdom
| | - Jonathan J Wilson
- School of Psychology, Cardiff University, Cardiff CF10 3AT, United Kingdom
- Neuroscience and Mental Health Innovation Institute, Cardiff CF24 4HQ, United Kingdom
| | - Seralynne D Vann
- School of Psychology, Cardiff University, Cardiff CF10 3AT, United Kingdom
- Neuroscience and Mental Health Innovation Institute, Cardiff CF24 4HQ, United Kingdom
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3
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Muessig L, Ribeiro Rodrigues F, Bjerknes TL, Towse BW, Barry C, Burgess N, Moser EI, Moser MB, Cacucci F, Wills TJ. Environment geometry alters subiculum boundary vector cell receptive fields in adulthood and early development. Nat Commun 2024; 15:982. [PMID: 38302455 PMCID: PMC10834499 DOI: 10.1038/s41467-024-45098-1] [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: 05/03/2023] [Accepted: 01/15/2024] [Indexed: 02/03/2024] Open
Abstract
Boundaries to movement form a specific class of landmark information used for navigation: Boundary Vector Cells (BVCs) are neurons which encode an animal's location as a vector displacement from boundaries. Here we characterise the prevalence and spatial tuning of subiculum BVCs in adult and developing male rats, and investigate the relationship between BVC spatial firing and boundary geometry. BVC directional tunings align with environment walls in squares, but are uniformly distributed in circles, demonstrating that environmental geometry alters BVC receptive fields. Inserted barriers uncover both excitatory and inhibitory components to BVC receptive fields, demonstrating that inhibitory inputs contribute to BVC field formation. During post-natal development, subiculum BVCs mature slowly, contrasting with the earlier maturation of boundary-responsive cells in upstream Entorhinal Cortex. However, Subiculum and Entorhinal BVC receptive fields are altered by boundary geometry as early as tested, suggesting this is an inherent feature of the hippocampal representation of space.
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Affiliation(s)
- Laurenz Muessig
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | | | - Tale L Bjerknes
- Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - Benjamin W Towse
- Institute of Cognitive Neuroscience, University College London, London, WC1N 3AZ, UK
| | - Caswell Barry
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - Neil Burgess
- Institute of Cognitive Neuroscience, University College London, London, WC1N 3AZ, UK
- UCL Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Edvard I Moser
- Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - May-Britt Moser
- Kavli Institute for Systems Neuroscience, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - Francesca Cacucci
- Department of Neuroscience, Physiology and Pharmacology; University College London, London, WC1E 6BT, UK
| | - Thomas J Wills
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK.
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4
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Friedenberger Z, Harkin E, Tóth K, Naud R. Silences, spikes and bursts: Three-part knot of the neural code. J Physiol 2023; 601:5165-5193. [PMID: 37889516 DOI: 10.1113/jp281510] [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: 02/13/2023] [Accepted: 09/28/2023] [Indexed: 10/28/2023] Open
Abstract
When a neuron breaks silence, it can emit action potentials in a number of patterns. Some responses are so sudden and intense that electrophysiologists felt the need to single them out, labelling action potentials emitted at a particularly high frequency with a metonym - bursts. Is there more to bursts than a figure of speech? After all, sudden bouts of high-frequency firing are expected to occur whenever inputs surge. The burst coding hypothesis advances that the neural code has three syllables: silences, spikes and bursts. We review evidence supporting this ternary code in terms of devoted mechanisms for burst generation, synaptic transmission and synaptic plasticity. We also review the learning and attention theories for which such a triad is beneficial.
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Affiliation(s)
- Zachary Friedenberger
- Brain and Mind Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Centre for Neural Dynamics and Artifical Intelligence, Department of Physics, University of Ottawa, Ottawa, Ontario, Ottawa
| | - Emerson Harkin
- Brain and Mind Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Katalin Tóth
- Brain and Mind Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Richard Naud
- Brain and Mind Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Centre for Neural Dynamics and Artifical Intelligence, Department of Physics, University of Ottawa, Ottawa, Ontario, Ottawa
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5
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Islam A, Saito T, Saido T, Ali AB. Presubiculum principal cells are preserved from degeneration in knock-in APP/TAU mouse models of Alzheimer's disease. Semin Cell Dev Biol 2023; 139:55-72. [PMID: 35292192 PMCID: PMC10439011 DOI: 10.1016/j.semcdb.2022.03.001] [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: 12/24/2021] [Revised: 02/25/2022] [Accepted: 03/03/2022] [Indexed: 12/31/2022]
Abstract
The presubiculum (PRS) is an integral component of the perforant pathway that has recently been recognised as a relatively unscathed region in clinical Alzheimer's disease (AD), despite neighbouring components of the perforant pathway, CA1 and the entorhinal cortex, responsible for formation of episodic memory and storage, showing severe hallmarks of AD including, amyloid-beta (Aβ) plaques, tau tangles and marked gliosis. However, the question remains whether this anatomical resilience translates into functional resilience of the PRS neurons. Using neuroanatomy combined with whole-cell electrophysiological recordings, we investigated whether the unique spatial profile of the PRS was replicable in two knock-in mouse models of AD, APPNL-F/NL-F, and APPNL-F/MAPTHTAU and whether the intrinsic properties and morphological integrity of the PRS principal neurons was maintained compared to the lateral entorhinal cortex (LEC) and hippocampal CA1 principal cells. Our data revealed an age-dependent Aβ and tau pathology with neuroinflammation in the LEC and CA1, but a presence of fleece-like Aβ deposits with an absence of tau tangles and cellular markers of gliosis in the PRS of the mouse models at 11-16 and 18-22 months. These observations were consistent in human post-mortem AD tissue. This spatial profile also correlated with functional resilience of strong burst firing PRS pyramidal cells that showed unaltered sub- and suprathreshold intrinsic biophysical membrane properties and gross morphology in the AD models that were similar to the properties of pyramidal cells recorded in age-matched wild-type mice (11-14 months). This was in contrast to the LEC and CA1 principal cells which showed altered subthreshold intrinsic properties such as a higher input resistance, longer membrane time constants and hyperexcitability in response to suprathreshold stimulation that correlated with atrophied dendrites in both AD models. In conclusion, our data show for the first time that the unique anatomical profile of the PRS constitutes a diffuse AD pathology that is correlated with the preservation of principal pyramidal cell intrinsic biophysical and morphological properties despite alteration of LEC and CA1 pyramidal cells in two distinct genetic models of AD. Understanding the underlying mechanisms of this resilience could be beneficial in preventing the spread of disease pathology before cognitive deficits are precipitated in AD.
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Affiliation(s)
- Anam Islam
- UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Takashi Saito
- Department of Neurocognitive Science, Institute of Brain Science, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8601, Japan
| | - Takaomi Saido
- RIKEN Center for Brain Science, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Afia B Ali
- UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK.
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6
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Joksimovic SM, Ghodsi SM, Heinsbroek JA, Orfila JE, Busquet N, Tesic V, Valdez R, Fine-Raquet B, Jevtovic-Todorovic V, Raol YH, Herson PS, Todorovic SM. Ca V3.1 T-type calcium channels are important for spatial memory processing in the dorsal subiculum. Neuropharmacology 2023; 226:109400. [PMID: 36586474 PMCID: PMC9898223 DOI: 10.1016/j.neuropharm.2022.109400] [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: 08/26/2022] [Revised: 12/16/2022] [Accepted: 12/20/2022] [Indexed: 12/29/2022]
Abstract
The dorsal subiculum (dSub) is one of the key structures responsible for the formation of hippocampal memory traces but the contribution of individual ionic currents to its cognitive function is not well studied. Although we recently reported that low-voltage-activated T-type calcium channels (T-channels) are crucial for the burst firing pattern regulation in the dSub pyramidal neurons, their potential role in learning and memory remains unclear. Here we used in vivo local field potential recordings and miniscope calcium imaging in freely behaving mice coupled with pharmacological and genetic tools to address this gap in knowledge. We show that the CaV3.1 isoform of T-channels is critically involved in controlling neuronal activity in the dSub in vivo. Altering neuronal excitability by inhibiting T-channel activity markedly affects calcium dynamics, synaptic plasticity, neuronal oscillations and phase-amplitude coupling in the dSub, thereby disrupting spatial learning. These results provide an important causative link between the CaV3.1 channels, burst firing of dSub neurons and memory formation, thus further supporting the notion that changes in neuronal excitability regulate memory processing. We posit that subicular CaV3.1 T-channels could be a promising novel drug target for cognitive disorders.
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Affiliation(s)
- Srdjan M Joksimovic
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Division of Neurology and CHOP Research Institute, Children's Hospital of Philadelphia, Philadelphia, PA, USA; Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Seyed Mohammadreza Ghodsi
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Jasper A Heinsbroek
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Neuroscience Graduate Program, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - James E Orfila
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Department of Neurological Surgery, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Nicolas Busquet
- Department of Neurology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Vesna Tesic
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Robert Valdez
- Department of Pediatrics, Division of Neurology, Translational Epilepsy Research Program, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Brier Fine-Raquet
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Vesna Jevtovic-Todorovic
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Department of Pharmacology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Yogendra H Raol
- Department of Pediatrics, Division of Neurology, Translational Epilepsy Research Program, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; National Institute of Neurological Disorders and Stroke, National Institutes of Health, Rockville, MD, USA
| | - Paco S Herson
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Department of Neurological Surgery, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Slobodan M Todorovic
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA; Neuroscience Graduate Program, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA.
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7
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Talpo F, Spaiardi P, Castagno AN, Maniezzi C, Raffin F, Terribile G, Sancini G, Pisani A, Biella GR. Neuromodulatory functions exerted by oxytocin on different populations of hippocampal neurons in rodents. Front Cell Neurosci 2023; 17:1082010. [PMID: 36816855 PMCID: PMC9932910 DOI: 10.3389/fncel.2023.1082010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 01/16/2023] [Indexed: 02/05/2023] Open
Abstract
Oxytocin (OT) is a neuropeptide widely known for its peripheral hormonal effects (i.e., parturition and lactation) and central neuromodulatory functions, related especially to social behavior and social, spatial, and episodic memory. The hippocampus is a key structure for these functions, it is innervated by oxytocinergic fibers, and contains OT receptors (OTRs). The hippocampal OTR distribution is not homogeneous among its subregions and types of neuronal cells, reflecting the specificity of oxytocin's modulatory action. In this review, we describe the most recent discoveries in OT/OTR signaling in the hippocampus, focusing primarily on the electrophysiological oxytocinergic modulation of the OTR-expressing hippocampal neurons. We then look at the effect this modulation has on the balance of excitation/inhibition and synaptic plasticity in each hippocampal subregion. Additionally, we review OTR downstream signaling, which underlies the OT effects observed in different types of hippocampal neuron. Overall, this review comprehensively summarizes the advancements in unraveling the neuromodulatory functions exerted by OT on specific hippocampal networks.
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Affiliation(s)
- Francesca Talpo
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy
| | - Paolo Spaiardi
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy,Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia, Italy
| | - Antonio Nicolas Castagno
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy
| | - Claudia Maniezzi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Francesca Raffin
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy
| | - Giulia Terribile
- Department of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy
| | - Giulio Sancini
- Department of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy,Nanomedicine Center, Neuroscience Center, School of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy
| | - Antonio Pisani
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy,Neurological Institute Foundation Casimiro Mondino (IRCCS), Pavia, Italy
| | - Gerardo Rosario Biella
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy,Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia, Italy,*Correspondence: Gerardo Rosario Biella,
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8
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Basal Forebrain Cholinergic Innervation Induces Depression-Like Behaviors Through Ventral Subiculum Hyperactivation. Neurosci Bull 2022; 39:617-630. [PMID: 36342657 PMCID: PMC10073402 DOI: 10.1007/s12264-022-00962-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/12/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractMalfunction of the ventral subiculum (vSub), the main subregion controlling the output connections from the hippocampus, is associated with major depressive disorder (MDD). Although the vSub receives cholinergic innervation from the medial septum and diagonal band of Broca (MSDB), whether and how the MSDB-to-vSub cholinergic circuit is involved in MDD is elusive. Here, we found that chronic unpredictable mild stress (CUMS) induced depression-like behaviors with hyperactivation of vSub neurons, measured by c-fos staining and whole-cell patch-clamp recording. By retrograde and anterograde tracing, we confirmed the dense MSDB cholinergic innervation of the vSub. In addition, transient restraint stress in CUMS increased the level of ACh in the vSub. Furthermore, chemogenetic stimulation of this MSDB-vSub innervation in ChAT-Cre mice induced hyperactivation of vSub pyramidal neurons along with depression-like behaviors; and local infusion of atropine, a muscarinic receptor antagonist, into the vSub attenuated the depression-like behaviors induced by chemogenetic stimulation of this pathway and CUMS. Together, these findings suggest that activating the MSDB-vSub cholinergic pathway induces hyperactivation of vSub pyramidal neurons and depression-like behaviors, revealing a novel circuit underlying vSub pyramidal neuronal hyperactivation and its associated depression.
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9
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Bhasin G, Nair IR. Dynamic Hippocampal CA2 Responses to Contextual Spatial Novelty. Front Syst Neurosci 2022; 16:923911. [PMID: 36003545 PMCID: PMC9393711 DOI: 10.3389/fnsys.2022.923911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/17/2022] [Indexed: 11/13/2022] Open
Abstract
Hippocampal place cells are functional units of spatial navigation and are present in all subregions: CA1, CA2, CA3, and CA4. Recent studies on CA2 have indicated its role in social and contextual memories, but its contribution to spatial novelty detection and encoding remains largely unknown. The current study aims to uncover how CA2 processes spatial novelty and to distinguish its functional role towards the same from CA1. Accordingly, a novel 3-day paradigm was designed where animals were introduced to a completely new environment on the first day, and on subsequent days, novel segments were inserted into the existing spatial environment while the other segments remained the same, allowing us to compare novel and familiar parts of the same closed-loop track on multiple days. We found that spatial novelty leads to dynamic and complex hippocampal place cell firings at both individual neuron and population levels. Place cells in both CA1 and CA2 had strong responses to novel segments, leading to higher average firing rates and increased pairwise cross correlations across all days. However, CA2 place cells that fired for novel areas had lower spatial information scores than CA1 place cells active in the same areas. At the ensemble level, CA1 only responded to spatial novelty on day 1, when the environment was completely novel, whereas CA2 responded to it on all days, each time novelty was introduced. Therefore, CA2 was more sensitive and responsive to novel spatial features even when introduced in a familiar environment, unlike CA1.
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10
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Mizuseki K, Kitanishi T. Oscillation-coordinated, noise-resistant information distribution via the subiculum. Curr Opin Neurobiol 2022; 75:102556. [DOI: 10.1016/j.conb.2022.102556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/15/2022] [Accepted: 04/19/2022] [Indexed: 11/03/2022]
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11
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Corrigan BW, Gulli RA, Doucet G, Roussy M, Luna R, Pradeepan KS, Sachs AJ, Martinez-Trujillo JC. Distinct neural codes in primate hippocampus and lateral prefrontal cortex during associative learning in virtual environments. Neuron 2022; 110:2155-2169.e4. [PMID: 35561675 DOI: 10.1016/j.neuron.2022.04.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 02/24/2022] [Accepted: 04/14/2022] [Indexed: 11/26/2022]
Abstract
The hippocampus (HPC) and the lateral prefrontal cortex (LPFC) are two cortical areas of the primate brain deemed essential to cognition. Here, we hypothesized that the codes mediating neuronal communication in the HPC and LPFC microcircuits have distinctively evolved to serve plasticity and memory function at different spatiotemporal scales. We used a virtual reality task in which animals selected one of the two targets in the arms of the maze, according to a learned context-color rule. Our results show that during associative learning, HPC principal cells concentrate spikes in bursts, enabling temporal summation and fast synaptic plasticity in small populations of neurons and ultimately facilitating rapid encoding of associative memories. On the other hand, layer II/III LPFC pyramidal cells fire spikes more sparsely distributed over time. The latter would facilitate broadcasting of signals loaded in short-term memory across neuronal populations without necessarily triggering fast synaptic plasticity.
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Affiliation(s)
- Benjamin W Corrigan
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada; Robarts Research Institute, University of Western Ontario, London, ON, Canada; Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Roberto A Gulli
- Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY, USA
| | | | - Megan Roussy
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada; Robarts Research Institute, University of Western Ontario, London, ON, Canada; Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Rogelio Luna
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada; Robarts Research Institute, University of Western Ontario, London, ON, Canada
| | - Kartik S Pradeepan
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada; Robarts Research Institute, University of Western Ontario, London, ON, Canada; Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Adam J Sachs
- The Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada
| | - Julio C Martinez-Trujillo
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada; Robarts Research Institute, University of Western Ontario, London, ON, Canada; Brain and Mind Institute, University of Western Ontario, London, ON, Canada; Lawson Health Research Institute, London, ON, Canada.
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12
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Intrinsic bursts facilitate learning of Lévy flight movements in recurrent neural network models. Sci Rep 2022; 12:4951. [PMID: 35322813 PMCID: PMC8943163 DOI: 10.1038/s41598-022-08953-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/09/2022] [Indexed: 11/24/2022] Open
Abstract
Isolated spikes and bursts of spikes are thought to provide the two major modes of information coding by neurons. Bursts are known to be crucial for fundamental processes between neuron pairs, such as neuronal communications and synaptic plasticity. Neuronal bursting also has implications in neurodegenerative diseases and mental disorders. Despite these findings on the roles of bursts, whether and how bursts have an advantage over isolated spikes in the network-level computation remains elusive. Here, we demonstrate in a computational model that not isolated spikes, but intrinsic bursts can greatly facilitate learning of Lévy flight random walk trajectories by synchronizing burst onsets across a neural population. Lévy flight is a hallmark of optimal search strategies and appears in cognitive behaviors such as saccadic eye movements and memory retrieval. Our results suggest that bursting is crucial for sequence learning by recurrent neural networks when sequences comprise long-tailed distributed discrete jumps.
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13
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Yu Q, Song S, Ma C, Pan L, Tan KC. Synaptic Learning With Augmented Spikes. IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS 2022; 33:1134-1146. [PMID: 33471768 DOI: 10.1109/tnnls.2020.3040969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Traditional neuron models use analog values for information representation and computation, while all-or-nothing spikes are employed in the spiking ones. With a more brain-like processing paradigm, spiking neurons are more promising for improvements in efficiency and computational capability. They extend the computation of traditional neurons with an additional dimension of time carried by all-or-nothing spikes. Could one benefit from both the accuracy of analog values and the time-processing capability of spikes? In this article, we introduce a concept of augmented spikes to carry complementary information with spike coefficients in addition to spike latencies. New augmented spiking neuron model and synaptic learning rules are proposed to process and learn patterns of augmented spikes. We provide systematic insights into the properties and characteristics of our methods, including classification of augmented spike patterns, learning capacity, construction of causality, feature detection, robustness, and applicability to practical tasks, such as acoustic and visual pattern recognition. Our augmented approaches show several advanced learning properties and reliably outperform the baseline ones that use typical all-or-nothing spikes. Our approaches significantly improve the accuracies of a temporal-based approach on sound and MNIST recognition tasks to 99.38% and 97.90%, respectively, highlighting the effectiveness and potential merits of our methods. More importantly, our augmented approaches are versatile and can be easily generalized to other spike-based systems, contributing to a potential development for them, including neuromorphic computing.
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14
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Turk AZ, Bishop M, Adeck A, SheikhBahaei S. Astrocytic modulation of central pattern generating motor circuits. Glia 2022; 70:1506-1519. [PMID: 35212422 DOI: 10.1002/glia.24162] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 12/26/2022]
Abstract
Central pattern generators (CPGs) generate the rhythmic and coordinated neural features necessary for the proper conduction of complex behaviors. In particular, CPGs are crucial for complex motor behaviors such as locomotion, mastication, respiration, and vocal production. While the importance of these networks in modulating behavior is evident, the mechanisms driving these CPGs are still not fully understood. On the other hand, accumulating evidence suggests that astrocytes have a significant role in regulating the function of some of these CPGs. Here, we review the location, function, and role of astrocytes in locomotion, respiration, and mastication CPGs and propose that, similarly, astrocytes may also play a significant role in the vocalization CPG.
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Affiliation(s)
- Ariana Z Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Mitchell Bishop
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Afuh Adeck
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
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15
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Lee SM, Seol JM, Lee I. Subicular neurons represent multiple variables of a hippocampal-dependent task by using theta rhythm. PLoS Biol 2022; 20:e3001546. [PMID: 35100261 PMCID: PMC8830791 DOI: 10.1371/journal.pbio.3001546] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 02/10/2022] [Accepted: 01/18/2022] [Indexed: 01/31/2023] Open
Abstract
The subiculum is positioned at a critical juncture at the interface of the hippocampus with the rest of the brain. However, the exact roles of the subiculum in most hippocampal-dependent memory tasks remain largely unknown. One obstacle to make comparisons of neural firing patterns between the subiculum and hippocampus is the broad firing fields of the subicular cells. Here, we used spiking phases in relation to theta rhythm to parse the broad firing field of a subicular neuron into multiple subfields to find the unique functional contribution of the subiculum while male rats performed a hippocampal-dependent visual scene memory task. Some of the broad firing fields of the subicular neurons were successfully divided into multiple subfields similar to those in the CA1 by using the theta phase precession cycle. The new paradigm significantly improved the detection of task-relevant information in subicular cells without affecting the information content represented by CA1 cells. Notably, we found that multiple fields of a single subicular neuron, unlike those in the CA1, carried heterogeneous task-related information such as visual context and choice response. Our findings suggest that the subicular cells integrate multiple task-related factors by using theta rhythm to associate environmental context with action.
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Affiliation(s)
- Su-Min Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea
| | - Jae-Min Seol
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea
| | - Inah Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea
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Shao J, Liu Y, Gao D, Tu J, Yang F. Neural Burst Firing and Its Roles in Mental and Neurological Disorders. Front Cell Neurosci 2021; 15:741292. [PMID: 34646123 PMCID: PMC8502892 DOI: 10.3389/fncel.2021.741292] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 08/26/2021] [Indexed: 11/29/2022] Open
Abstract
Neural firing patterns are critical for specific information coding and transmission, and abnormal firing is implicated in a series of neural pathologies. Recent studies have indicated that enhanced burst firing mediated by T-type voltage-gated calcium channels (T-VGCCs) in specific neuronal subtypes is involved in several mental or neurological disorders such as depression and epilepsy, while suppression of T-VGCCs relieve related symptoms. Burst firing consists of groups of relatively high-frequency spikes separated by quiescence. Neurons in a variety of brain areas, including the thalamus, hypothalamus, cortex, and hippocampus, display burst firing, but the ionic mechanisms that generating burst firing and the related physiological functions vary among regions. In this review, we summarize recent findings on the mechanisms underlying burst firing in various brain areas, as well as the roles of burst firing in several mental and neurological disorders. We also discuss the ion channels and receptors that may regulate burst firing directly or indirectly, with these molecules highlighted as potential intervention targets for the treatment of mental and neurological disorders.
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Affiliation(s)
- Jie Shao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Yunhui Liu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China
| | - Dashuang Gao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Jie Tu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Fan Yang
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
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17
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Rayi PR, Kaphzan H. Electrophysiological Characterization of Regular and Burst Firing Pyramidal Neurons of the Dorsal Subiculum in an Angelman Syndrome Mouse Model. Front Cell Neurosci 2021; 15:670998. [PMID: 34512263 PMCID: PMC8427506 DOI: 10.3389/fncel.2021.670998] [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: 02/22/2021] [Accepted: 08/04/2021] [Indexed: 11/21/2022] Open
Abstract
Angelman syndrome (AS) is a debilitating neurogenetic disorder characterized by severe developmental delay, speech impairment, gait ataxia, sleep disturbances, epilepsy, and a unique behavioral phenotype. AS is caused by a microdeletion or mutation in the maternal 15q11-q13 chromosome region containing UBE3A gene. The hippocampus is one of the important brain regions affected in AS mice leading to substantial hippocampal-dependent cognitive and behavioral deficits. Recent studies have suggested an abnormal increase in the α1-Na/K-ATPase (α1-NaKA) in AS mice as the precipitating factor leading to the hippocampal deficits. A subsequent study showed that the hippocampal-dependent behavioral deficits occur as a result of altered calcium (Ca+2) dynamics in the CA1 pyramidal neurons (PNs) caused by the elevated α1-NaKA expression levels in the AS mice. Nonetheless, a causal link between hippocampal deficits and major behavioral phenotypes in AS is still obscure. Subiculum, a region adjacent to the hippocampal CA1 is the major output source of the hippocampus and plays an important role in the transfer of information from the CA1 region to the cortical areas. However, in spite of the robust hippocampal deficits and several known electrophysiological alterations in multiple brain regions in AS mice, the neuronal properties of the subicular neurons were never investigated in these mice. Additionally, subicular function is also implied in many neuropsychiatric disorders such as autism, schizophrenia, Alzheimer’s disease, and epilepsy that share some common features with AS. Therefore, given the importance of the subiculum in these neuropsychiatric disorders and the altered electrophysiological properties of the hippocampal CA1 PNs projecting to the subiculum, we sought to examine the subicular PNs. We performed whole-cell recordings from dorsal subiculum of both WT and AS mice and found three distinct populations of PNs based on their ability to fire bursts or single action potentials following somatic current injection: strong bursting, weak bursting, and regular firing neurons. We found no overall differences in the distribution of these different subicular PN populations among AS and WT controls. However, the different cell types showed distinct alterations in their intrinsic membrane properties. Further, none of these populations were altered in their excitatory synaptic properties. Altogether, our study characterized the different subtypes of PNs in the subicular region of an AS mouse model.
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Affiliation(s)
- Prudhvi Raj Rayi
- Sagol Department of Neurobiology, The Integrated Brain and Behavior Research Center, University of Haifa, Haifa, Israel
| | - Hanoch Kaphzan
- Sagol Department of Neurobiology, The Integrated Brain and Behavior Research Center, University of Haifa, Haifa, Israel
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18
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Aggleton JP, Yanakieva S, Sengpiel F, Nelson AJ. The separate and combined properties of the granular (area 29) and dysgranular (area 30) retrosplenial cortex. Neurobiol Learn Mem 2021; 185:107516. [PMID: 34481970 DOI: 10.1016/j.nlm.2021.107516] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/27/2021] [Accepted: 08/30/2021] [Indexed: 12/31/2022]
Abstract
Retrosplenial cortex contains two principal subdivisions, area 29 (granular) and area 30 (dysgranular). Their respective anatomical connections in the rat brain reveal that area 29 is the primary recipient of hippocampal and parahippocampal spatial and contextual information while area 30 is the primary interactor with current visual information. Lesion studies and measures of neuronal activity in rodents indicate that retrosplenial cortex helps to integrate space from different perspectives, e.g., egocentric and allocentric, providing landmark and heading cues for navigation and spatial learning. It provides a repository of scene information that, over time, becomes increasingly independent of the hippocampus. These processes, reflect the interactive actions between areas 29 and 30, along with their convergent influences on cortical and thalamic targets. Consequently, despite their differences, both areas 29 and 30 are necessary for an array of spatial and learning problems.
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Affiliation(s)
- John P Aggleton
- School of Psychology, Cardiff University, Tower Building, Park Place, Cardiff, Wales CF10 3AT, UK.
| | - Steliana Yanakieva
- School of Psychology, Cardiff University, Tower Building, Park Place, Cardiff, Wales CF10 3AT, UK
| | - Frank Sengpiel
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, Wales CF10 3AX, UK
| | - Andrew J Nelson
- School of Psychology, Cardiff University, Tower Building, Park Place, Cardiff, Wales CF10 3AT, UK
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19
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Climer JR, Dombeck DA. Information Theoretic Approaches to Deciphering the Neural Code with Functional Fluorescence Imaging. eNeuro 2021; 8:ENEURO.0266-21.2021. [PMID: 34433574 PMCID: PMC8474651 DOI: 10.1523/eneuro.0266-21.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 07/22/2021] [Accepted: 08/04/2021] [Indexed: 11/21/2022] Open
Abstract
Information theoretic metrics have proven useful in quantifying the relationship between behaviorally relevant parameters and neuronal activity with relatively few assumptions. However, these metrics are typically applied to action potential (AP) recordings and were not designed for the slow timescales and variable amplitudes typical of functional fluorescence recordings (e.g., calcium imaging). The lack of research guidelines on how to apply and interpret these metrics with fluorescence traces means the neuroscience community has yet to realize the power of information theoretic metrics. Here, we used computational methods to create mock AP traces with known amounts of information. From these, we generated fluorescence traces and examined the ability of different information metrics to recover the known information values. We provide guidelines for how to use information metrics when applying them to functional fluorescence and demonstrate their appropriate application to GCaMP6f population recordings from mouse hippocampal neurons imaged during virtual navigation.
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Affiliation(s)
- Jason R Climer
- Department of Neurobiology, Northwestern University, Evanston, 60208 IL
| | - Daniel A Dombeck
- Department of Neurobiology, Northwestern University, Evanston, 60208 IL
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20
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Frost BE, Martin SK, Cafalchio M, Islam MN, Aggleton JP, O'Mara SM. Anterior Thalamic Inputs Are Required for Subiculum Spatial Coding, with Associated Consequences for Hippocampal Spatial Memory. J Neurosci 2021; 41:6511-6525. [PMID: 34131030 PMCID: PMC8318085 DOI: 10.1523/jneurosci.2868-20.2021] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 03/24/2021] [Accepted: 03/28/2021] [Indexed: 11/21/2022] Open
Abstract
Just as hippocampal lesions are principally responsible for "temporal lobe" amnesia, lesions affecting the anterior thalamic nuclei seem principally responsible for a similar loss of memory, "diencephalic" amnesia. Compared with the former, the causes of diencephalic amnesia have remained elusive. A potential clue comes from how the two sites are interconnected, as within the hippocampal formation, only the subiculum has direct, reciprocal connections with the anterior thalamic nuclei. We found that both permanent and reversible anterior thalamic nuclei lesions in male rats cause a cessation of subicular spatial signaling, reduce spatial memory performance to chance, but leave hippocampal CA1 place cells largely unaffected. We suggest that a core element of diencephalic amnesia stems from the information loss in hippocampal output regions following anterior thalamic pathology.SIGNIFICANCE STATEMENT At present, we know little about interactions between temporal lobe and diencephalic memory systems. Here, we focused on the subiculum, as the sole hippocampal formation region directly interconnected with the anterior thalamic nuclei. We combined reversible and permanent lesions of the anterior thalamic nuclei, electrophysiological recordings of the subiculum, and behavioral analyses. Our results were striking and clear: following permanent thalamic lesions, the diverse spatial signals normally found in the subiculum (including place cells, grid cells, and head-direction cells) all disappeared. Anterior thalamic lesions had no discernible impact on hippocampal CA1 place fields. Thus, spatial firing activity within the subiculum requires anterior thalamic function, as does successful spatial memory performance. Our findings provide a key missing part of the much bigger puzzle concerning why anterior thalamic damage is so catastrophic for spatial memory in rodents and episodic memory in humans.
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Affiliation(s)
- Bethany E Frost
- School of Psychology and Institute of Neuroscience, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Sean K Martin
- School of Psychology and Institute of Neuroscience, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Matheus Cafalchio
- School of Psychology and Institute of Neuroscience, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Md Nurul Islam
- School of Psychology and Institute of Neuroscience, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - John P Aggleton
- School of Psychology, Cardiff University, Cardiff, CF10 3AS, United Kingdom
| | - Shane M O'Mara
- School of Psychology and Institute of Neuroscience, Trinity College Dublin, Dublin, D02 PN40, Ireland
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21
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Brennan EKW, Jedrasiak-Cape I, Kailasa S, Rice SP, Sudhakar SK, Ahmed OJ. Thalamus and claustrum control parallel layer 1 circuits in retrosplenial cortex. eLife 2021; 10:e62207. [PMID: 34170817 PMCID: PMC8233040 DOI: 10.7554/elife.62207] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 05/17/2021] [Indexed: 11/13/2022] Open
Abstract
The granular retrosplenial cortex (RSG) is critical for both spatial and non-spatial behaviors, but the underlying neural codes remain poorly understood. Here, we use optogenetic circuit mapping in mice to reveal a double dissociation that allows parallel circuits in superficial RSG to process disparate inputs. The anterior thalamus and dorsal subiculum, sources of spatial information, strongly and selectively recruit small low-rheobase (LR) pyramidal cells in RSG. In contrast, neighboring regular-spiking (RS) cells are preferentially controlled by claustral and anterior cingulate inputs, sources of mostly non-spatial information. Precise sublaminar axonal and dendritic arborization within RSG layer 1, in particular, permits this parallel processing. Observed thalamocortical synaptic dynamics enable computational models of LR neurons to compute the speed of head rotation, despite receiving head direction inputs that do not explicitly encode speed. Thus, parallel input streams identify a distinct principal neuronal subtype ideally positioned to support spatial orientation computations in the RSG.
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Affiliation(s)
- Ellen KW Brennan
- Department of Psychology, University of MichiganAnn ArborUnited States
- Neuroscience Graduate Program, University of MichiganAnn ArborUnited States
| | | | - Sameer Kailasa
- Department of Mathematics, University of MichiganAnn ArborUnited States
| | - Sharena P Rice
- Department of Psychology, University of MichiganAnn ArborUnited States
- Neuroscience Graduate Program, University of MichiganAnn ArborUnited States
| | | | - Omar J Ahmed
- Department of Psychology, University of MichiganAnn ArborUnited States
- Neuroscience Graduate Program, University of MichiganAnn ArborUnited States
- Michigan Center for Integrative Research in Critical Care, University of MichiganAnn ArborUnited States
- Kresge Hearing Research Institute, University of MichiganAnn ArborUnited States
- Department of Biomedical Engineering, University of MichiganAnn ArborUnited States
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22
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Song S, Ma C, Sun W, Xu J, Dang J, Yu Q. Efficient learning with augmented spikes: A case study with image classification. Neural Netw 2021; 142:205-212. [PMID: 34023641 DOI: 10.1016/j.neunet.2021.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 02/15/2021] [Accepted: 05/06/2021] [Indexed: 10/21/2022]
Abstract
Efficient learning of spikes plays a valuable role in training spiking neural networks (SNNs) to have desired responses to input stimuli. However, current learning rules are limited to a binary form of spikes. The seemingly ubiquitous phenomenon of burst in nervous systems suggests a new way to carry more information with spike bursts in addition to times. Based on this, we introduce an advanced form, the augmented spikes, where spike coefficients are used to carry additional information. How could neurons learn and benefit from augmented spikes remains unclear. In this paper, we propose two new efficient learning rules to process spatiotemporal patterns composed of augmented spikes. Moreover, we examine the learning abilities of our methods with a synthetic recognition task of augmented spike patterns and two practical ones for image classification. Experimental results demonstrate that our rules are capable of extracting information carried by both the timing and coefficient of spikes. Our proposed approaches achieve remarkable performance and good robustness under various noise conditions, as compared to benchmarks. The improved performance indicates the merits of augmented spikes and our learning rules, which could be beneficial and generalized to a broad range of spike-based platforms.
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Affiliation(s)
- Shiming Song
- Tianjin Key Laboratory of Cognitive Computing and Application, College of Intelligence and Computing, Tianjin University, Tianjin, 300350, China
| | - Chenxiang Ma
- Tianjin Key Laboratory of Cognitive Computing and Application, College of Intelligence and Computing, Tianjin University, Tianjin, 300350, China
| | - Wei Sun
- Tianjin Key Laboratory of Cognitive Computing and Application, College of Intelligence and Computing, Tianjin University, Tianjin, 300350, China
| | - Junhai Xu
- Tianjin Key Laboratory of Cognitive Computing and Application, College of Intelligence and Computing, Tianjin University, Tianjin, 300350, China
| | - Jianwu Dang
- Tianjin Key Laboratory of Cognitive Computing and Application, College of Intelligence and Computing, Tianjin University, Tianjin, 300350, China
| | - Qiang Yu
- Tianjin Key Laboratory of Cognitive Computing and Application, College of Intelligence and Computing, Tianjin University, Tianjin, 300350, China.
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23
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Brennan EKW, Sudhakar SK, Jedrasiak-Cape I, John TT, Ahmed OJ. Hyperexcitable Neurons Enable Precise and Persistent Information Encoding in the Superficial Retrosplenial Cortex. Cell Rep 2021; 30:1598-1612.e8. [PMID: 32023472 DOI: 10.1016/j.celrep.2019.12.093] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 10/25/2019] [Accepted: 12/27/2019] [Indexed: 11/29/2022] Open
Abstract
The retrosplenial cortex (RSC) is essential for memory and navigation, but the neural codes underlying these functions remain largely unknown. Here, we show that the most prominent cell type in layers 2/3 (L2/3) of the mouse granular RSC is a hyperexcitable, small pyramidal cell. These cells have a low rheobase (LR), high input resistance, lack of spike frequency adaptation, and spike widths intermediate to those of neighboring fast-spiking (FS) inhibitory neurons and regular-spiking (RS) excitatory neurons. LR cells are excitatory but rarely synapse onto neighboring neurons. Instead, L2/3 is a feedforward, not feedback, inhibition-dominated network with dense connectivity between FS cells and from FS to LR neurons. Biophysical models of LR but not RS cells precisely and continuously encode sustained input from afferent postsubicular head-direction cells. Thus, the distinct intrinsic properties of LR neurons can support both the precision and persistence necessary to encode information over multiple timescales in the RSC.
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Affiliation(s)
- Ellen K W Brennan
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | | | | | - Tibin T John
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Omar J Ahmed
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA; Michigan Center for Integrative Research in Critical Care, University of Michigan, Ann Arbor, MI 48109, USA; Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
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24
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Bant JS, Hardcastle K, Ocko SA, Giocomo LM. Topography in the Bursting Dynamics of Entorhinal Neurons. Cell Rep 2021; 30:2349-2359.e7. [PMID: 32075768 DOI: 10.1016/j.celrep.2020.01.057] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 11/28/2019] [Accepted: 01/17/2020] [Indexed: 12/18/2022] Open
Abstract
Medial entorhinal cortex contains neural substrates for representing space. These substrates include grid cells that fire in repeating locations and increase in scale progressively along the dorsal-to-ventral entorhinal axis, with the physical distance between grid firing nodes increasing from tens of centimeters to several meters in rodents. Whether the temporal scale of grid cell spiking dynamics shows a similar dorsal-to-ventral organization remains unknown. Here, we report the presence of a dorsal-to-ventral gradient in the temporal spiking dynamics of grid cells in behaving mice. This gradient in bursting supports the emergence of a dorsal grid cell population with a high signal-to-noise ratio. In vitro recordings combined with a computational model point to a role for gradients in non-inactivating sodium conductances in supporting the bursting gradient in vivo. Taken together, these results reveal a complementary organization in the temporal and intrinsic properties of entorhinal cells.
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Affiliation(s)
- Jason S Bant
- Department of Neurobiology, Stanford University School of Medicine, Stanford CA 94305, USA
| | - Kiah Hardcastle
- Department of Neurobiology, Stanford University School of Medicine, Stanford CA 94305, USA
| | - Samuel A Ocko
- Department of Applied Physics, Stanford University, Stanford CA 94305, USA
| | - Lisa M Giocomo
- Department of Neurobiology, Stanford University School of Medicine, Stanford CA 94305, USA.
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25
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Kitanishi T, Umaba R, Mizuseki K. Robust information routing by dorsal subiculum neurons. SCIENCE ADVANCES 2021; 7:7/11/eabf1913. [PMID: 33692111 PMCID: PMC7946376 DOI: 10.1126/sciadv.abf1913] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 01/25/2021] [Indexed: 05/27/2023]
Abstract
The dorsal hippocampus conveys various information associated with spatial navigation; however, how the information is distributed to multiple downstream areas remains unknown. We investigated this by identifying axonal projections using optogenetics during large-scale recordings from the rat subiculum, the major hippocampal output structure. Subicular neurons demonstrated a noise-resistant representation of place, speed, and trajectory, which was as accurate as or even more accurate than that of hippocampal CA1 neurons. Speed- and trajectory-dependent firings were most prominent in neurons projecting to the retrosplenial cortex and nucleus accumbens, respectively. Place-related firing was uniformly observed in neurons targeting the retrosplenial cortex, nucleus accumbens, anteroventral thalamus, and medial mammillary body. Theta oscillations and sharp-wave/ripples tightly controlled the firing of projection neurons in a target region-specific manner. In conclusion, the dorsal subiculum robustly routes diverse navigation-associated information to downstream areas.
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Affiliation(s)
- Takuma Kitanishi
- Department of Physiology, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan.
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Ryoko Umaba
- Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan
| | - Kenji Mizuseki
- Department of Physiology, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan.
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26
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Fei F, Wang X, Wang Y, Chen Z. Dissecting the role of subiculum in epilepsy: Research update and translational potential. Prog Neurobiol 2021; 201:102029. [PMID: 33636224 DOI: 10.1016/j.pneurobio.2021.102029] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 01/12/2021] [Accepted: 02/21/2021] [Indexed: 11/25/2022]
Abstract
The subiculum serves as the strategic core output of the hippocampus, through which neural activity exits the hippocampal proper and targets the entorhinal cortex and other more distant subcortical and cortical areas. The past decade has witnessed a growing interest in the subiculum, owing to discoveries revealing its critical role in regulating many physiological and pathophysiological processes. Notably, accumulating evidence from both clinical and experimental studies suggests that the subiculum plays a vital role in seizure initiation and propagation, in epilepsy. In this review, we briefly describe the structure and connectivity of the subiculum and then summarize the molecular and cellular mechanisms in the subiculum underlying the epileptic brain, in both epilepsy patients and animal models. Next, we review some translational approaches targeting the malfunctioned subiculum to treat epilepsy. Finally, we pose open questions for future research in the subiculum and their clinical translation challenges.
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Affiliation(s)
- Fan Fei
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Xia Wang
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yi Wang
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China; Key Laboratory of Neuropharmacology and Translational Medicine of Zhejiang Province, College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology & Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China; Key Laboratory of Neuropharmacology and Translational Medicine of Zhejiang Province, College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, China; Epilepsy Center, Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
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27
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Lévesque M, Avoli M. The subiculum and its role in focal epileptic disorders. Rev Neurosci 2020; 32:249-273. [PMID: 33661586 DOI: 10.1515/revneuro-2020-0091] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 09/29/2020] [Indexed: 01/07/2023]
Abstract
The subicular complex (hereafter referred as subiculum), which is reciprocally connected with the hippocampus and rhinal cortices, exerts a major control on hippocampal outputs. Over the last three decades, several studies have revealed that the subiculum plays a pivotal role in learning and memory but also in pathological conditions such as mesial temporal lobe epilepsy (MTLE). Indeed, subicular networks actively contribute to seizure generation and this structure is relatively spared from the cell loss encountered in this focal epileptic disorder. In this review, we will address: (i) the functional properties of subicular principal cells under normal and pathological conditions; (ii) the subiculum role in sustaining seizures in in vivo models of MTLE and in in vitro models of epileptiform synchronization; (iii) its presumptive role in human MTLE; and (iv) evidence underscoring the relationship between subiculum and antiepileptic drug effects. The studies reviewed here reinforce the view that the subiculum represents a limbic area with relevant, as yet unexplored, roles in focal epilepsy.
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Affiliation(s)
- Maxime Lévesque
- Departments of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, H3A 2B4Québec, Canada
| | - Massimo Avoli
- Departments of Neurology, Neurosurgery, and Physiology, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, H3A 2B4Québec, Canada
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28
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Yanagihara S, Ikebuchi M, Mori C, Tachibana RO, Okanoya K. Arousal State-Dependent Alterations in Neural Activity in the Zebra Finch VTA/SNc. Front Neurosci 2020; 14:897. [PMID: 32973441 PMCID: PMC7472990 DOI: 10.3389/fnins.2020.00897] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/31/2020] [Indexed: 11/13/2022] Open
Abstract
Sleep-wake behaviors are important for survival and highly conserved among animal species. A growing body of evidence indicates that the midbrain dopaminergic system is associated with sleep-wake regulation in mammals. Songbirds exhibit mammalian-like sleep structures, and neurons in the midbrain ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) possess physiological properties similar to those in mammals. However, it remains uncertain whether the neurons in the songbird VTA/SNc are associated with sleep-wake regulation. Here, we show that VTA/SNc neurons in zebra finches exhibit arousal state-dependent alterations in spontaneous neural activity. By recording extracellular single-unit activity from anesthetized or freely behaving zebra finches, we found that VTA/SNc neurons exhibited increased firing rates during wakefulness, and the same population of neurons displayed reduced firing rates during anesthesia and slow-wave sleep. These results suggest that the songbird VTA/SNc is associated with the regulation of sleep and wakefulness along with other arousal regulatory systems. These findings raise the possibility that fundamental neural mechanisms of sleep-wake behaviors are evolutionarily conserved between birds and mammals.
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Affiliation(s)
- Shin Yanagihara
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | | | - Chihiro Mori
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | | | - Kazuo Okanoya
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.,RIKEN Center for Brain Science, Wako, Japan
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29
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Spike Afterpotentials Shape the In Vivo Burst Activity of Principal Cells in Medial Entorhinal Cortex. J Neurosci 2020; 40:4512-4524. [PMID: 32332120 DOI: 10.1523/jneurosci.2569-19.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 04/03/2020] [Accepted: 04/11/2020] [Indexed: 11/21/2022] Open
Abstract
Principal neurons in rodent medial entorhinal cortex (MEC) generate high-frequency bursts during natural behavior. While in vitro studies point to potential mechanisms that could support such burst sequences, it remains unclear whether these mechanisms are effective under in vivo conditions. In this study, we focused on the membrane-potential dynamics immediately following action potentials (APs), as measured in whole-cell recordings from male mice running in virtual corridors (Domnisoru et al., 2013). These afterpotentials consisted either of a hyperpolarization, an extended ramp-like shoulder, or a depolarization reminiscent of depolarizing afterpotentials (DAPs) recorded in vitro in MEC principal neurons. Next, we correlated the afterpotentials with the cells' propensity to fire bursts. All DAP cells with known location resided in Layer II, generated bursts, and their interspike intervals (ISIs) were typically between 5 and 15 ms. The ISI distributions of Layer-II cells without DAPs peaked sharply at around 4 ms and varied only minimally across that group. This dichotomy in burst behavior is explained by cell-group-specific DAP dynamics. The same two groups of bursting neurons also emerged when we clustered extracellular spike-train autocorrelations measured in real 2D arenas (Latuske et al., 2015). Apart from slight variations in grid spacing, no difference in the spatial coding properties of the grid cells across all three groups was discernible. Layer III neurons were only sparsely bursting (SB) and had no DAPs. As various mechanisms for modulating ion-channels underlying DAPs exist, our results suggest that temporal features of MEC activity can be altered while maintaining the cells' overall spatial tuning characteristics.SIGNIFICANCE STATEMENT Depolarizing afterpotentials (DAPs) are frequently observed in principal neurons from slice preparations of rodent medial entorhinal cortex (MEC), but their functional role in vivo is unknown. Analyzing whole-cell data from mice running on virtual tracks, we show that DAPs do occur during behavior. Cells with prominent DAPs are found in Layer II; their interspike intervals (ISIs) reflect DAP time-scales. In contrast, neither the rarely bursting cells in Layer III, nor the high-frequency bursters in Layer II, have a DAP. Extracellular recordings from mice exploring real 2D arenas demonstrate that grid cells within these three groups have similar spatial coding properties. We conclude that DAPs shape the temporal response characteristics of principal neurons in MEC with little effect on spatial properties.
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Fiske MP, Anstötz M, Welty LJ, Maccaferri G. The intrinsic cell type-specific excitatory connectivity of the developing mouse subiculum is sufficient to generate synchronous epileptiform activity. J Physiol 2020; 598:1965-1985. [PMID: 32119127 DOI: 10.1113/jp279561] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 02/18/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The activity of local excitatory circuits of the subiculum has been suggested to be involved in the initiation of pathological activity in epileptic patients and experimental animal models of temporal lobe epilepsy. We have taken advantage of multimodal techniques to classify subicular cells in distinct subclasses and have investigated their morphofunctional properties and connectivity in vitro. Our results indicate that local subicular excitatory circuits are connected in a cell type-specific fashion and that synapses are preferentially established on basal vs. apical dendrites. We show that local excitatory circuits, isolated from extrasubicular inputs and pharmacologically disinhibited, are sufficient to initiate synchronous epileptiform activity in vitro. In conclusion, this work provides a high-resolution description of local excitatory circuits of the subiculum and highlights their mechanistic involvement in the generation of pathological activity. ABSTRACT The subiculum has been suggested to be involved in the initiation of pathological discharges in human patients and animal models of temporal lobe epilepsy. Although converging evidence has revealed the existence of functional diversity within its principal neurons, much less attention has been devoted to its intrinsic connectivity and whether its local excitatory circuits are sufficient to generate epileptiform activity. Here, we have directly addressed these two key points in mouse subicular slices. First, using multivariate techniques, we have distinguished two groups of principal cells, which we have termed type 1 and type 2. These subgroups roughly overlap with what were classically indicated as regular and bursting cells, and showed differences in the extension and complexity of their apical dendrites. Functional connectivity was found both between similar (homotypic) and different (heterotypic) types of cells, with a marked asymmetry within heterotypic pairs. Unitary excitatory postsynaptic potentials (uEPSPs) revealed a high degree of variability both in amplitude, failure rate, rise time and half-width. Post hoc analysis of functionally connected pairs suggested that the observed uEPSPs were mediated by few contact sites, predominantly located on the basal dendrites. When surgically isolated from extrasubicular excitatory afferents, pharmacologically disinhibited subicular slices generated hyper-synchronous discharges. Thus, we conclude that local subicular excitatory circuits, connected according to cell type-specific rules, are sufficient to promote epileptiform activity. This conclusion fits well with a previous suggestion that local subicular events, purely mediated by excitatory connections, may underlie the pre-ictal discharges that govern interictal-ictal transitions.
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Affiliation(s)
- Michael Patrick Fiske
- Northwestern University Interdepartmental PhD Program & Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Max Anstötz
- Northwestern University Interdepartmental PhD Program & Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Leah J Welty
- Biostatistics Collaboration Center, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Gianmaria Maccaferri
- Northwestern University Interdepartmental PhD Program & Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
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31
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Valero M, English DF. Head-mounted approaches for targeting single-cells in freely moving animals. J Neurosci Methods 2019; 326:108397. [DOI: 10.1016/j.jneumeth.2019.108397] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/30/2019] [Accepted: 08/06/2019] [Indexed: 12/11/2022]
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O’Mara SM, Aggleton JP. Space and Memory (Far) Beyond the Hippocampus: Many Subcortical Structures Also Support Cognitive Mapping and Mnemonic Processing. Front Neural Circuits 2019; 13:52. [PMID: 31447653 PMCID: PMC6692652 DOI: 10.3389/fncir.2019.00052] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 07/22/2019] [Indexed: 11/13/2022] Open
Abstract
Memory research remains focused on just a few brain structures-in particular, the hippocampal formation (the hippocampus and entorhinal cortex). Three key discoveries promote this continued focus: the striking demonstrations of enduring anterograde amnesia after bilateral hippocampal damage; the realization that synapses in the hippocampal formation are plastic e.g., when responding to short bursts of patterned stimulation ("long-term potentiation" or LTP); and the discovery of a panoply of spatially-tuned cells, principally surveyed in the hippocampal formation (place cells coding for position; head-direction cells, providing compass-like information; and grid cells, providing a metric for 3D space). Recent anatomical, behavioral, and electrophysiological work extends this picture to a growing network of subcortical brain structures, including the anterior thalamic nuclei, rostral midline thalamic nuclei, and the claustrum. There are, for example, spatially-tuned cells in all of these regions, including cells with properties similar to place cells of the hippocampus proper. These findings add new perspectives to what had been originally been proposed-but often overlooked-half a century ago: that damage to an extended network of structures connected to the hippocampal formation results in diencephalic amnesia. We suggest these new findings extend spatial signaling in the brain far beyond the hippocampal formation, with profound implications for theories of the neural bases of spatial and mnemonic functions.
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Affiliation(s)
- Shane M. O’Mara
- School of Psychology and Institute of Neuroscience, Trinity College, Dublin, Ireland
| | - John P. Aggleton
- School of Psychology, Cardiff University, Cardiff, United Kingdom
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