1
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Ohara S, Yoshino R, Kimura K, Kawamura T, Tanabe S, Zheng A, Nakamura S, Inoue KI, Takada M, Tsutsui KI, Witter MP. Laminar Organization of the Entorhinal Cortex in Macaque Monkeys Based on Cell-Type-Specific Markers and Connectivity. Front Neural Circuits 2021; 15:790116. [PMID: 34949991 PMCID: PMC8688913 DOI: 10.3389/fncir.2021.790116] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 11/16/2021] [Indexed: 11/13/2022] Open
Abstract
The entorhinal cortex (EC) is a major gateway between the hippocampus and telencephalic structures, and plays a critical role in memory and navigation. Through the use of various molecular markers and genetic tools, neuron types constituting EC are well studied in rodents, and their layer-dependent distributions, connections, and functions have also been characterized. In primates, however, such cell-type-specific understandings are lagging. To bridge the gap between rodents and primates, here we provide the first cell-type-based global map of EC in macaque monkeys. The laminar organization of the monkey EC was systematically examined and compared with that of the rodent EC by using immunohistochemistry for molecular markers which have been well characterized in the rodent EC: reelin, calbindin, and Purkinje cell protein 4 (PCP4). We further employed retrograde neuron labeling from the nucleus accumbens and amygdala to identify the EC output layer. This cell-type-based approach enabled us to apply the latest laminar definition of rodent EC to monkeys. Based on the similarity of the laminar organization, the monkey EC can be divided into two subdivisions: rostral and caudal EC. These subdivisions likely correspond to the lateral and medial EC in rodents, respectively. In addition, we found an overall absence of a clear laminar arrangement of layer V neurons in the rostral EC, unlike rodents. The cell-type-based architectural map provided in this study will accelerate the application of genetic tools in monkeys for better understanding of the role of EC in memory and navigation.
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Affiliation(s)
- Shinya Ohara
- Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.,PRESTO, Japan Science and Technology Agency (JST), Tokyo, Japan
| | - Rintaro Yoshino
- Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Kei Kimura
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Japan
| | - Taichi Kawamura
- Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Soshi Tanabe
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Japan
| | - Andi Zheng
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Japan
| | - Shinya Nakamura
- Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Ken-Ichi Inoue
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Japan
| | - Masahiko Takada
- Systems Neuroscience Section, Department of Neuroscience, Primate Research Institute, Kyoto University, Inuyama, Japan
| | - Ken-Ichiro Tsutsui
- Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.,Laboratory of Systems Neuroscience, Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Menno P Witter
- Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.,Laboratory of Systems Neuroscience, Graduate School of Medicine, Tohoku University, Sendai, Japan.,Department of Developmental Neuroscience, Graduate School of Medicine, Tohoku University, Sendai, Japan
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2
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Gerlei KZ, Brown CM, Sürmeli G, Nolan MF. Deep entorhinal cortex: from circuit organization to spatial cognition and memory. Trends Neurosci 2021; 44:876-887. [PMID: 34593254 DOI: 10.1016/j.tins.2021.08.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 08/05/2021] [Accepted: 08/08/2021] [Indexed: 10/20/2022]
Abstract
The deep layers of the entorhinal cortex are important for spatial cognition, as well as memory storage, consolidation and retrieval. A long-standing hypothesis is that deep-layer neurons relay spatial and memory-related signals between the hippocampus and telencephalon. We review the implications of recent circuit-level analyses that suggest more complex roles. The organization of deep entorhinal layers is consistent with multi-stage processing by specialized cell populations; in this framework, hippocampal, neocortical, and subcortical inputs are integrated to generate representations for use by targets in the telencephalon and for feedback to the superficial entorhinal cortex and hippocampus. Addressing individual sublayers of the deep entorhinal cortex in future experiments and models will be important for establishing systems-level mechanisms for spatial cognition and episodic memory.
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Affiliation(s)
- Klára Z Gerlei
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Christina M Brown
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Gülşen Sürmeli
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Matthew F Nolan
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK.
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3
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Kumar A, Arya H, Tamta K, Maurya RC. Acute stress-induced neuronal plasticity in the corticoid complex of 15-day-old chick, Gallus domesticus. J Anat 2021; 239:869-891. [PMID: 34159582 PMCID: PMC8450486 DOI: 10.1111/joa.13483] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 05/17/2021] [Accepted: 05/25/2021] [Indexed: 12/01/2022] Open
Abstract
Several studies conducted on chicken have shown that a single stress exposure may impair or improve memory as well as learning processes. However, to date, stress effects on neuronal morphology are poorly investigated wherefore it was of interest to evaluate this further in chicks. Thus, the present study aims to investigate the role of single acute stress (AS) of 24 h food and water deprivation in neuronal plasticity in terms of spine density of the corticoid complex (CC) in 15-day-old chick, Gallus domesticus, by using three neurohistological techniques: Cresyl Violet, Golgi Colonnier, and Golgi Cox technique. The dorsolateral surface of the cerebral hemisphere is occupied by CC which can be differentiated into two subfields: an intermediate corticoid (CI) subfield (arranged in layers) and a dorsolateral corticoid (CDL) subfield. Based on different criteria such as soma shape, dendritic branching pattern, and dendritic spine density, two main moderately spinous groups of neuronal cells were observed in the CC, namely, projection neurons (comprising of multipolar and pyramidal neurons) and stellate neurons. In the present study, the stellate neurons have shown a significant decrease as well as an increase in their spine density in both CI and CDL subfields, whereas the multipolar neurons had shown a significant increase in their spine density in the CDL region only. The present study shows that AS induces neuronal plasticity in terms of spine density in both CI and CDL neurons. The morphological changes in the form of decreased dendritic branches due to stress have been observed in the CI region in comparison to CDL region, which could be linked to more effect of stress in this region. The avian CDL corresponds to the entorhinal cortex of mammals on the basis of neuronal morphology and bidirectional connections between adjacent areas. The projection neurons increase their branches and also their spine number to cope with the stress effects, while the stellate neurons show contrasting effect in their spine density. Therefore, this study will establish that slight modifications in natural stimuli or environmental changes faced by the animal may affect their dorsolateral forebrain which shows neuronal plasticity that help in the development of an adaptive capacity of the animal to survive under changing environmental conditions.
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Affiliation(s)
- Adarsh Kumar
- Department of Zoology (DST‐FIST Sponsored)Kumaun UniversityAlmoraIndia
| | - Hemlata Arya
- Department of Zoology (DST‐FIST Sponsored)Kumaun UniversityAlmoraIndia
| | - Kavita Tamta
- Department of Zoology (DST‐FIST Sponsored)Kumaun UniversityAlmoraIndia
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4
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Ohara S, Blankvoort S, Nair RR, Nigro MJ, Nilssen ES, Kentros C, Witter MP. Local projections of layer Vb-to-Va are more prominent in lateral than in medial entorhinal cortex. eLife 2021; 10:e67262. [PMID: 33769282 PMCID: PMC8051944 DOI: 10.7554/elife.67262] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/25/2021] [Indexed: 11/13/2022] Open
Abstract
The entorhinal cortex, in particular neurons in layer V, allegedly mediate transfer of information from the hippocampus to the neocortex, underlying long-term memory. Recently, this circuit has been shown to comprise a hippocampal output recipient layer Vb and a cortical projecting layer Va. With the use of in vitro electrophysiology in transgenic mice specific for layer Vb, we assessed the presence of the thus necessary connection from layer Vb-to-Va in the functionally distinct medial (MEC) and lateral (LEC) subdivisions; MEC, particularly its dorsal part, processes allocentric spatial information, whereas the corresponding part of LEC processes information representing elements of episodes. Using identical experimental approaches, we show that connections from layer Vb-to-Va neurons are stronger in dorsal LEC compared with dorsal MEC, suggesting different operating principles in these two regions. Although further in vivo experiments are needed, our findings imply a potential difference in how LEC and MEC mediate episodic systems consolidation.
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Grants
- endowment Kavli Foundation
- infrastructure grant NORBRAIN,#197467 Norwegian Research Council
- the Centre of Excellence scheme - Centre for Neural Computation,#223262 Norwegian Research Council
- research grant,# 227769 Norwegian Research Council
- KAKENHI,#19K06917 Ministry of Education, Culture, Sports, Science and Technology
- KAKENHI (#19K06917) Ministry of Education, Culture, Sports, Science and Technology
- #197467 Norwegian Research Council
- #223262 Norwegian Research Council
- #227769 Norwegian Research Council
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Affiliation(s)
- Shinya Ohara
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
- Laboratory of Systems Neuroscience, Tohoku University Graduate School of Life SciencesTohokuJapan
| | - Stefan Blankvoort
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Rajeevkumar Raveendran Nair
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Maximiliano J Nigro
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Eirik S Nilssen
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Clifford Kentros
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
| | - Menno P Witter
- Kavli institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheimNorway
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Witter MP, Amaral DG. The entorhinal cortex of the monkey: VI. Organization of projections from the hippocampus, subiculum, presubiculum, and parasubiculum. J Comp Neurol 2020; 529:828-852. [DOI: 10.1002/cne.24983] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/29/2020] [Accepted: 06/30/2020] [Indexed: 12/14/2022]
Affiliation(s)
- Menno P. Witter
- Department of Psychiatry and Behavioral Sciences The MIND Institute and the California National Primate Research Center Davis California USA
| | - David G. Amaral
- Department of Psychiatry and Behavioral Sciences The MIND Institute and the California National Primate Research Center Davis California USA
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6
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Komendantov AO, Venkadesh S, Rees CL, Wheeler DW, Hamilton DJ, Ascoli GA. Quantitative firing pattern phenotyping of hippocampal neuron types. Sci Rep 2019; 9:17915. [PMID: 31784578 PMCID: PMC6884469 DOI: 10.1038/s41598-019-52611-w] [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: 03/07/2019] [Accepted: 09/20/2019] [Indexed: 01/19/2023] Open
Abstract
Systematically organizing the anatomical, molecular, and physiological properties of cortical neurons is important for understanding their computational functions. Hippocampome.org defines 122 neuron types in the rodent hippocampal formation based on their somatic, axonal, and dendritic locations, putative excitatory/inhibitory outputs, molecular marker expression, and biophysical properties. We augmented the electrophysiological data of this knowledge base by collecting, quantifying, and analyzing the firing responses to depolarizing current injections for every hippocampal neuron type from published experiments. We designed and implemented objective protocols to classify firing patterns based on 5 transients (delay, adapting spiking, rapidly adapting spiking, transient stuttering, and transient slow-wave bursting) and 4 steady states (non-adapting spiking, persistent stuttering, persistent slow-wave bursting, and silence). This automated approach revealed 9 unique (plus one spurious) families of firing pattern phenotypes while distinguishing potential new neuronal subtypes. Novel statistical associations emerged between firing responses and other electrophysiological properties, morphological features, and molecular marker expression. The firing pattern parameters, experimental conditions, spike times, references to the original empirical evidences, and analysis scripts are released open-source through Hippocampome.org for all neuron types, greatly enhancing the existing search and browse capabilities. This information, collated online in human- and machine-accessible form, will help design and interpret both experiments and model simulations.
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Affiliation(s)
- Alexander O Komendantov
- Krasnow Institute for Advanced Study, George Mason University, 4400 University Drive, MS 2A1, Fairfax, Virginia, 2230, USA.
| | - Siva Venkadesh
- Krasnow Institute for Advanced Study, George Mason University, 4400 University Drive, MS 2A1, Fairfax, Virginia, 2230, USA
| | - Christopher L Rees
- Krasnow Institute for Advanced Study, George Mason University, 4400 University Drive, MS 2A1, Fairfax, Virginia, 2230, USA
| | - Diek W Wheeler
- Krasnow Institute for Advanced Study, George Mason University, 4400 University Drive, MS 2A1, Fairfax, Virginia, 2230, USA
| | - David J Hamilton
- Krasnow Institute for Advanced Study, George Mason University, 4400 University Drive, MS 2A1, Fairfax, Virginia, 2230, USA
| | - Giorgio A Ascoli
- Krasnow Institute for Advanced Study, George Mason University, 4400 University Drive, MS 2A1, Fairfax, Virginia, 2230, USA.
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7
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Nilssen ES, Doan TP, Nigro MJ, Ohara S, Witter MP. Neurons and networks in the entorhinal cortex: A reappraisal of the lateral and medial entorhinal subdivisions mediating parallel cortical pathways. Hippocampus 2019; 29:1238-1254. [PMID: 31408260 DOI: 10.1002/hipo.23145] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 06/29/2019] [Accepted: 07/11/2019] [Indexed: 12/31/2022]
Abstract
In this review, we aim to reappraise the organization of intrinsic and extrinsic networks of the entorhinal cortex with a focus on the concept of parallel cortical connectivity streams. The concept of two entorhinal areas, the lateral and medial entorhinal cortex, belonging to two parallel input-output streams mediating the encoding and storage of respectively what and where information hinges on the claim that a major component of their cortical connections is with the perirhinal cortex and postrhinal or parahippocampal cortex in, respectively, rodents or primates. In this scenario, the lateral entorhinal cortex and the perirhinal cortex are connectionally associated and likewise the postrhinal/parahippocampal cortex and the medial entorhinal cortex are partners. In contrast, here we argue that the connectivity matrix emphasizes the potential of substantial integration of cortical information through interactions between the two entorhinal subdivisions and between the perirhinal and postrhinal/parahippocampal cortices, but most importantly through a new observation that the postrhinal/parahippocampal cortex projects to both lateral and medial entorhinal cortex. We suggest that entorhinal inputs provide the hippocampus with high-order complex representations of the external environment, its stability, as well as apparent changes either as an inherent feature of a biological environment or as the result of navigating the environment. This thus indicates that the current connectional model of the parahippocampal region as part of the medial temporal lobe memory system needs to be revised.
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Affiliation(s)
- Eirik S Nilssen
- Kavli Institute for Systems Neuroscience, Centre for Neural Computation, Egil and Pauline Braathen and Fred Kavli Centre for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway
| | - Thanh P Doan
- Kavli Institute for Systems Neuroscience, Centre for Neural Computation, Egil and Pauline Braathen and Fred Kavli Centre for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway
| | - Maximiliano J Nigro
- Kavli Institute for Systems Neuroscience, Centre for Neural Computation, Egil and Pauline Braathen and Fred Kavli Centre for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway
| | - Shinya Ohara
- Kavli Institute for Systems Neuroscience, Centre for Neural Computation, Egil and Pauline Braathen and Fred Kavli Centre for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway
- Laboratory of Systems Neuroscience, Tohoku University Graduate School of Life Sciences, Sendai, Japan
| | - Menno P Witter
- Kavli Institute for Systems Neuroscience, Centre for Neural Computation, Egil and Pauline Braathen and Fred Kavli Centre for Cortical Microcircuits, NTNU Norwegian University of Science and Technology, Trondheim, Norway
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8
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Egorov AV, Schumacher D, Medert R, Birnbaumer L, Freichel M, Draguhn A. TRPC channels are not required for graded persistent activity in entorhinal cortex neurons. Hippocampus 2019; 29:1038-1048. [PMID: 31002217 DOI: 10.1002/hipo.23094] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 12/19/2022]
Abstract
Adaptive behavior requires the transient storage of information beyond the physical presence of external stimuli. This short-lasting form of memory involves sustained ("persistent") neuronal firing which may be generated by cell-autonomous biophysical properties of neurons or/and neural circuit dynamics. A number of studies from brain slices reports intrinsically generated persistent firing in cortical excitatory neurons following suprathreshold depolarization by intracellular current injection. In layer V (LV) neurons of the medial entorhinal cortex (mEC) persistent firing depends on the activation of cholinergic muscarinic receptors and is mediated by a calcium-activated nonselective cation current (ICAN ). The molecular identity of this conductance remains, however, unknown. Recently, it has been suggested that the underlying ion channels belong to the canonical transient receptor potential (TRPC) channel family and include heterotetramers of TRPC1/5, TRPC1/4, and/or TRPC1/4/5 channels. While this suggestion was based on pharmacological experiments and on effects of TRP-interacting peptides, an unambiguous proof based on TRPC channel-depleted animals is pending. Here, we used two different lines of TRPC channel knockout mice, either lacking TRPC1-, TRPC4-, and TRPC5-containing channels or lacking all seven members of the TRPC family. We report unchanged persistent activity in mEC LV neurons in these animals, ruling out that muscarinic-dependent persistent activity depends on TRPC channels.
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Affiliation(s)
- Alexei V Egorov
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Dagmar Schumacher
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Rebekka Medert
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Lutz Birnbaumer
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, Durham, North Carolina, USA.,School of Medical Sciences, Catholic University of Argentina, Institute of Biomedical Research (BIOMED UCA-CONICET), Buenos Aires, Argentina
| | - Marc Freichel
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Andreas Draguhn
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
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9
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Ohara S, Onodera M, Simonsen ØW, Yoshino R, Hioki H, Iijima T, Tsutsui KI, Witter MP. Intrinsic Projections of Layer Vb Neurons to Layers Va, III, and II in the Lateral and Medial Entorhinal Cortex of the Rat. Cell Rep 2018; 24:107-116. [DOI: 10.1016/j.celrep.2018.06.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 05/04/2018] [Accepted: 06/01/2018] [Indexed: 12/29/2022] Open
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10
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Smirnova EY, Amakhin DV, Malkin SL, Chizhov AV, Zaitsev AV. Acute Changes in Electrophysiological Properties of Cortical Regular-Spiking Cells Following Seizures in a Rat Lithium–Pilocarpine Model. Neuroscience 2018; 379:202-215. [DOI: 10.1016/j.neuroscience.2018.03.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Revised: 03/14/2018] [Accepted: 03/15/2018] [Indexed: 11/26/2022]
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11
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Septal cholinergic neurons gate hippocampal output to entorhinal cortex via oriens lacunosum moleculare interneurons. Proc Natl Acad Sci U S A 2018; 115:E1886-E1895. [PMID: 29437952 DOI: 10.1073/pnas.1712538115] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neuromodulation of neural networks, whereby a selected circuit is regulated by a particular modulator, plays a critical role in learning and memory. Among neuromodulators, acetylcholine (ACh) plays a critical role in hippocampus-dependent memory and has been shown to modulate neuronal circuits in the hippocampus. However, it has remained unknown how ACh modulates hippocampal output. Here, using in vitro and in vivo approaches, we show that ACh, by activating oriens lacunosum moleculare (OLM) interneurons and therefore augmenting the negative-feedback regulation to the CA1 pyramidal neurons, suppresses the circuit from the hippocampal area CA1 to the deep-layer entorhinal cortex (EC). We also demonstrate, using mouse behavior studies, that the ablation of OLM interneurons specifically impairs hippocampus-dependent but not hippocampus-independent learning. These data suggest that ACh plays an important role in regulating hippocampal output to the EC by activating OLM interneurons, which is critical for the formation of hippocampus-dependent memory.
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12
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Lin EC, Combe CL, Gasparini S. Differential Contribution of Ca 2+-Dependent Mechanisms to Hyperexcitability in Layer V Neurons of the Medial Entorhinal Cortex. Front Cell Neurosci 2017; 11:182. [PMID: 28713246 PMCID: PMC5491848 DOI: 10.3389/fncel.2017.00182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 06/13/2017] [Indexed: 11/13/2022] Open
Abstract
Temporal lobe epilepsy is characterized by recurrent seizures in one or both temporal lobes of the brain; some in vitro models show that epileptiform discharges initiate in entorhinal layer V neurons and then spread into other areas of the temporal lobe. We previously found that, in the presence of GABAA receptor antagonists, stimulation of afferent fibers, terminating both at proximal and distal dendritic locations, initiated hyperexcitable bursts in layer V medial entorhinal neurons. We investigated the differential contribution of Ca2+-dependent mechanisms to the plateaus underlying these bursts at proximal and distal synapses. We found that the NMDA glutamatergic antagonist D,L-2-amino-5-phosphonovaleric acid (APV; 50 μM) reduced both the area and duration of the bursts at both proximal and distal synapses by about half. The L-type Ca2+ channel blocker nimodipine (10 μM) and the R- and T-type Ca2+ channel blocker NiCl2 (200 μM) decreased the area of the bursts to a lesser extent; none of these effects appeared to be location-dependent. Remarkably, the perfusion of flufenamic acid (FFA; 100 μM), to block Ca2+-activated non-selective cation currents (ICAN) mediated by transient receptor potential (TRP) channels, had a location-dependent effect, by abolishing burst firing and switching the suprathreshold response to a single action potential (AP) for proximal stimulation, but only minimally affecting the bursts evoked by distal stimulation. A similar outcome was found when FFA was pressure-applied locally around the proximal dendrite of the recorded neurons and in the presence of a selective blocker of melastatin TRP (TRPM) channels, 9-phenanthrol (100 μM), whereas a selective blocker of canonical TRP (TRPC) channels, SKF 96365, did not affect the bursts. These results indicate that different mechanisms might contribute to the initiation of hyperexcitability in layer V neurons at proximal and distal synapses and could shed light on the initiation of epileptiform activity in the entorhinal cortex.
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Affiliation(s)
- Eric C Lin
- Neuroscience Center of Excellence, Louisiana State University Health Sciences CenterNew Orleans, LA, United States
| | - Crescent L Combe
- Neuroscience Center of Excellence, Louisiana State University Health Sciences CenterNew Orleans, LA, United States
| | - Sonia Gasparini
- Neuroscience Center of Excellence, Louisiana State University Health Sciences CenterNew Orleans, LA, United States.,Department of Cell Biology and Anatomy, Louisiana State University Health Sciences CenterNew Orleans, LA, United States
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13
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Witter MP, Doan TP, Jacobsen B, Nilssen ES, Ohara S. Architecture of the Entorhinal Cortex A Review of Entorhinal Anatomy in Rodents with Some Comparative Notes. Front Syst Neurosci 2017; 11:46. [PMID: 28701931 PMCID: PMC5488372 DOI: 10.3389/fnsys.2017.00046] [Citation(s) in RCA: 194] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/07/2017] [Indexed: 12/18/2022] Open
Abstract
The entorhinal cortex (EC) is the major input and output structure of the hippocampal formation, forming the nodal point in cortico-hippocampal circuits. Different division schemes including two or many more subdivisions have been proposed, but here we will argue that subdividing EC into two components, the lateral EC (LEC) and medial EC (MEC) might suffice to describe the functional architecture of EC. This subdivision then leads to an anatomical interpretation of the different phenotypes of LEC and MEC. First, we will briefly summarize the cytoarchitectonic differences and differences in hippocampal projection patterns on which the subdivision between LEC and MEC traditionally is based and provide a short comparative perspective. Second, we focus on main differences in cortical connectivity, leading to the conclusion that the apparent differences may well correlate with the functional differences. Cortical connectivity of MEC is features interactions with areas such as the presubiculum, parasubiculum, retrosplenial cortex (RSC) and postrhinal cortex, all areas that are considered to belong to the "spatial processing domain" of the cortex. In contrast, LEC is strongly connected with olfactory areas, insular, medial- and orbitofrontal areas and perirhinal cortex. These areas are likely more involved in processing of object information, attention and motivation. Third, we will compare the intrinsic networks involving principal- and inter-neurons in LEC and MEC. Together, these observations suggest that the different phenotypes of both EC subdivisions likely depend on the combination of intrinsic organization and specific sets of inputs. We further suggest a reappraisal of the notion of EC as a layered input-output structure for the hippocampal formation.
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Affiliation(s)
- Menno P. Witter
- Functional Neuroanatomy, KavlI Institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheim, Norway
| | - Thanh P. Doan
- Functional Neuroanatomy, KavlI Institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheim, Norway
| | - Bente Jacobsen
- Functional Neuroanatomy, KavlI Institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheim, Norway
| | - Eirik S. Nilssen
- Functional Neuroanatomy, KavlI Institute for Systems Neuroscience, Center for Computational Neuroscience, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, NTNU Norwegian University of Science and TechnologyTrondheim, Norway
| | - Shinya Ohara
- Division of Systems Neuroscience, Tohoku University Graduate School of Life ScienceSendai, Japan
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14
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Molecularly Defined Circuitry Reveals Input-Output Segregation in Deep Layers of the Medial Entorhinal Cortex. Neuron 2015; 88:1040-1053. [PMID: 26606996 PMCID: PMC4675718 DOI: 10.1016/j.neuron.2015.10.041] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 09/21/2015] [Accepted: 10/09/2015] [Indexed: 02/06/2023]
Abstract
Deep layers of the medial entorhinal cortex are considered to relay signals from the hippocampus to other brain structures, but pathways for routing of signals to and from the deep layers are not well established. Delineating these pathways is important for a circuit level understanding of spatial cognition and memory. We find that neurons in layers 5a and 5b have distinct molecular identities, defined by the transcription factors Etv1 and Ctip2, and divergent targets, with extensive intratelencephalic projections originating in layer 5a, but not 5b. This segregation of outputs is mirrored by the organization of glutamatergic input from stellate cells in layer 2 and from the hippocampus, with both preferentially targeting layer 5b over 5a. Our results suggest a molecular and anatomical organization of input-output computations in deep layers of the MEC, reveal precise translaminar microcircuitry, and identify molecularly defined pathways for spatial signals to influence computation in deep layers. The transcription factors Etv1 and Ctip2 distinguish entorhinal layers 5a and 5b Layer 5a has extensive intratelencephalic projections, but layer 5b does not Terminals of layer 2 stellate, but not pyramidal cells, are enriched in deep layers Hippocampal and stellate cell inputs preferentially target layer 5b neurons
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15
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Ramsden HL, Sürmeli G, McDonagh SG, Nolan MF. Laminar and dorsoventral molecular organization of the medial entorhinal cortex revealed by large-scale anatomical analysis of gene expression. PLoS Comput Biol 2015; 11:e1004032. [PMID: 25615592 PMCID: PMC4304787 DOI: 10.1371/journal.pcbi.1004032] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 11/10/2014] [Indexed: 12/14/2022] Open
Abstract
Neural circuits in the medial entorhinal cortex (MEC) encode an animal's position and orientation in space. Within the MEC spatial representations, including grid and directional firing fields, have a laminar and dorsoventral organization that corresponds to a similar topography of neuronal connectivity and cellular properties. Yet, in part due to the challenges of integrating anatomical data at the resolution of cortical layers and borders, we know little about the molecular components underlying this organization. To address this we develop a new computational pipeline for high-throughput analysis and comparison of in situ hybridization (ISH) images at laminar resolution. We apply this pipeline to ISH data for over 16,000 genes in the Allen Brain Atlas and validate our analysis with RNA sequencing of MEC tissue from adult mice. We find that differential gene expression delineates the borders of the MEC with neighboring brain structures and reveals its laminar and dorsoventral organization. We propose a new molecular basis for distinguishing the deep layers of the MEC and show that their similarity to corresponding layers of neocortex is greater than that of superficial layers. Our analysis identifies ion channel-, cell adhesion- and synapse-related genes as candidates for functional differentiation of MEC layers and for encoding of spatial information at different scales along the dorsoventral axis of the MEC. We also reveal laminar organization of genes related to disease pathology and suggest that a high metabolic demand predisposes layer II to neurodegenerative pathology. In principle, our computational pipeline can be applied to high-throughput analysis of many forms of neuroanatomical data. Our results support the hypothesis that differences in gene expression contribute to functional specialization of superficial layers of the MEC and dorsoventral organization of the scale of spatial representations.
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Affiliation(s)
- Helen L. Ramsden
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
- Neuroinformatics Doctoral Training Centre, School of Informatics, University of Edinburgh, Edinburgh, United Kingdom
| | - Gülşen Sürmeli
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | - Steven G. McDonagh
- Institute of Perception, Action and Behaviour, School of Informatics, University of Edinburgh, Edinburgh, United Kingdom
| | - Matthew F. Nolan
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
- Centre for Brain Development and Repair, inStem, Bangalore, India
- * E-mail:
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16
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Abstract
One of the grand challenges in neuroscience is to comprehend neural computation in the association cortices, the parts of the cortex that have shown the largest expansion and differentiation during mammalian evolution and that are thought to contribute profoundly to the emergence of advanced cognition in humans. In this Review, we use grid cells in the medial entorhinal cortex as a gateway to understand network computation at a stage of cortical processing in which firing patterns are shaped not primarily by incoming sensory signals but to a large extent by the intrinsic properties of the local circuit.
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17
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Srivastava U, Singh D, Kumar P. Neuronal classes and their specialization in the corticoid complex of a food-storing bird, the Indian House Crow (Corvus splendens). CAN J ZOOL 2014. [DOI: 10.1139/cjz-2013-0116] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neuronal classes and their specialization in the corticoid complex of a food-storing bird (the Indian House Crow, Corvus splendens Vieillot, 1817) have been investigated using Golgi and Cresyl-violet methods. The aim of present study is to observe the neuronal characteristics of corticoid complex of the House Crow (food-storing bird) and to compare them with that of a nonfood-storing bird (the Strawberry Finch, Estrilda amandava = Amandava amandava (L., 1758)). Three main neuronal classes, viz. projection neurons, local circuit neurons, and stellate neurons, have been identified in both intermediate corticoid area (CI) and dorsolateral corticoid area (CDL) based on soma shape, arrangement of dendrites around the soma, and axonal projection. Projection neurons have four neuronal subtypes: multipolar, pyramidal, pyramidal-like, and horizontal cells. It seems that the specialization in pyramidal, local circuit, and pyramidal-like neurons show advantages in the House Crow as a food-storing bird for better memory, cognition, and connectivity in corticoid complex. This is the first study of its kind that provides information regarding neuronal classes within the corticoid complex of a food-storing bird and a comparison between a food-storing bird (House Crow) and the only available study on a nonfood-storing bird (Strawberry Finch).
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Affiliation(s)
- U.C. Srivastava
- Department of Zoology, University of Allahabad, Allahabad, India-211002
| | - Durgesh Singh
- Department of Zoology, University of Allahabad, Allahabad, India-211002
| | - Prashant Kumar
- Department of Zoology, University of Allahabad, Allahabad, India-211002
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18
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Cellular, columnar and modular organization of spatial representations in medial entorhinal cortex. Curr Opin Neurobiol 2014; 24:47-54. [DOI: 10.1016/j.conb.2013.08.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 08/14/2013] [Accepted: 08/15/2013] [Indexed: 11/20/2022]
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19
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Greenhill SD, Chamberlain SEL, Lench A, Massey PV, Yuill KH, Woodhall GL, Jones RSG. Background synaptic activity in rat entorhinal cortex shows a progressively greater dominance of inhibition over excitation from deep to superficial layers. PLoS One 2014; 9:e85125. [PMID: 24454801 PMCID: PMC3893176 DOI: 10.1371/journal.pone.0085125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 11/22/2013] [Indexed: 11/21/2022] Open
Abstract
The entorhinal cortex (EC) controls hippocampal input and output, playing major roles in memory and spatial navigation. Different layers of the EC subserve different functions and a number of studies have compared properties of neurones across layers. We have studied synaptic inhibition and excitation in EC neurones, and we have previously compared spontaneous synaptic release of glutamate and GABA using patch clamp recordings of synaptic currents in principal neurones of layers II (L2) and V (L5). Here, we add comparative studies in layer III (L3). Such studies essentially look at neuronal activity from a presynaptic viewpoint. To correlate this with the postsynaptic consequences of spontaneous transmitter release, we have determined global postsynaptic conductances mediated by the two transmitters, using a method to estimate conductances from membrane potential fluctuations. We have previously presented some of this data for L3 and now extend to L2 and L5. Inhibition dominates excitation in all layers but the ratio follows a clear rank order (highest to lowest) of L2>L3>L5. The variance of the background conductances was markedly higher for excitation and inhibition in L2 compared to L3 or L5. We also show that induction of synchronized network epileptiform activity by blockade of GABA inhibition reveals a relative reluctance of L2 to participate in such activity. This was associated with maintenance of a dominant background inhibition in L2, whereas in L3 and L5 the absolute level of inhibition fell below that of excitation, coincident with the appearance of synchronized discharges. Further experiments identified potential roles for competition for bicuculline by ambient GABA at the GABAA receptor, and strychnine-sensitive glycine receptors in residual inhibition in L2. We discuss our results in terms of control of excitability in neuronal subpopulations of EC neurones and what these may suggest for their functional roles.
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Affiliation(s)
- Stuart David Greenhill
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | | | - Alex Lench
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | - Peter Vernon Massey
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, United Kingdom
| | - Kathryn Heather Yuill
- School of Biomedical & Healthcare Sciences, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, United Kingdom
| | - Gavin Lawrence Woodhall
- Aston Brain Centre, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
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20
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Witter MP, Canto CB, Couey JJ, Koganezawa N, O'Reilly KC. Architecture of spatial circuits in the hippocampal region. Philos Trans R Soc Lond B Biol Sci 2013; 369:20120515. [PMID: 24366129 DOI: 10.1098/rstb.2012.0515] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The hippocampal region contains several principal neuron types, some of which show distinct spatial firing patterns. The region is also known for its diversity in neural circuits and many have attempted to causally relate network architecture within and between these unique circuits to functional outcome. Still, much is unknown about the mechanisms or network properties by which the functionally specific spatial firing profiles of neurons are generated, let alone how they are integrated into a coherently functioning meta-network. In this review, we explore the architecture of local networks and address how they may interact within the context of an overarching space circuit, aiming to provide directions for future successful explorations.
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Affiliation(s)
- Menno P Witter
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, , 7030 Trondheim, Norway
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21
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Eggink H, Mertens P, Storm E, Giocomo LM. Hyperpolarization-activated cyclic nucleotide-gated 1 independent grid cell-phase precession in mice. Hippocampus 2013; 24:249-56. [DOI: 10.1002/hipo.22231] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/22/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Hannah Eggink
- Kavli Institute for Systems Neuroscience and The Centre for the Biology of Memory; The Norwegian Institute for Technology; Trondheim Norway
- Institute for Interdisciplinary Studies, University of Amsterdam; Amsterdam Netherlands
| | - Paul Mertens
- Kavli Institute for Systems Neuroscience and The Centre for the Biology of Memory; The Norwegian Institute for Technology; Trondheim Norway
- Institute for Interdisciplinary Studies, University of Amsterdam; Amsterdam Netherlands
| | - Eline Storm
- Kavli Institute for Systems Neuroscience and The Centre for the Biology of Memory; The Norwegian Institute for Technology; Trondheim Norway
| | - Lisa M. Giocomo
- Kavli Institute for Systems Neuroscience and The Centre for the Biology of Memory; The Norwegian Institute for Technology; Trondheim Norway
- Department of Neurobiology; Stanford University School of Medicine; Stanford California
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22
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Medinilla V, Johnson O, Gasparini S. Features of proximal and distal excitatory synaptic inputs to layer V neurons of the rat medial entorhinal cortex. J Physiol 2013; 591:169-83. [PMID: 23006478 PMCID: PMC3630779 DOI: 10.1113/jphysiol.2012.237172] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 09/19/2012] [Indexed: 11/08/2022] Open
Abstract
The entorhinal cortex (EC) has a fundamental function in transferring information between the hippocampus and the neocortex. EC layer V principal neurons are the main recipients of the hippocampal output and send processed information to the neocortex, likely playing an important role in memory processing and consolidation. Most of these neurons have apical dendrites that extend to the superficial layers and are rich in spines, which could be the targets of excitatory inputs from fibres innervating that region. We have used electrical stimulation of afferent fibres coupled with whole-cell patch-clamp somatic recordings to study the features of distal excitatory inputs and compare them with those of proximal ones. The amplitude of putative unitary excitatory responses was ∼1.5 times larger for distal compared with proximal inputs. The responses were purely glutamatergic, as they were abolished by a combination of AMPA and NMDA glutamatergic receptor antagonists. Blockade of I(h) by 4-ethylphenylamino-1,2-dimethyl-6-methylaminopyrimidinium chloride (ZD7288) increased temporal summation; the increase was comparable for proximal and distal inputs. Proximal inputs initiated a somatic spike more reliably than distal ones; in some instances, somatic action potentials triggered by distal stimulation were preceded by dendritic spikes that fully propagated to the soma. Altogether, our results show that medial layer V entorhinal neurons receive excitatory synapses at distal dendritic locations, which gives them access to information encoded by inputs to the superficial layers as well as the deep layers. These findings are fundamentally relevant to understanding the role of the EC in the formation and consolidation of episodic memory.
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Affiliation(s)
- Virginia Medinilla
- Neuroscience Center, Louisiana State University Health Sciences Center, 2020 Gravier Street, New Orleans, LA 70112, USA
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23
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Simonnet J, Eugène E, Cohen I, Miles R, Fricker D. Cellular neuroanatomy of rat presubiculum. Eur J Neurosci 2012; 37:583-97. [PMID: 23176296 DOI: 10.1111/ejn.12065] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/01/2012] [Accepted: 10/24/2012] [Indexed: 12/01/2022]
Abstract
The presubiculum, at the transition from the hippocampus to the cortex, is a key area for spatial information coding but the anatomical and physiological basis of presubicular function remains unclear. Here we correlated the structural and physiological properties of single neurons of the presubiculum in vitro. Unsupervised cluster analysis based on dendritic length and form, soma location, firing pattern and action potential properties allowed us to classify principal neurons into three major cell types. Cluster 1 consisted of a population of small regular spiking principal cells in layers II/III. Cluster 2 contained intrinsically burst firing pyramidal cells of layer IV, with a resting potential close to threshold. Cluster 3 included regular spiking cells of layers V and VI, and could be divided into subgroups 3.1 and 3.2. Cells of cluster 3.1 included pyramidal, multiform and inverted pyramidal cells. Cells of cluster 3.2 contained high-resistance pyramidal neurons that fired readily in response to somatic current injection. These data show that presubicular principal cells generally conform to neurons of the periarchicortex. However, the presence of intrinsic bursting cells in layer IV distinguishes the presubicular cortex from the neighbouring entorhinal cortex. The firing frequency adaptation was very low for principal cells of clusters 1 and 3, a property that should assist the generation of maintained head direction signals in vivo.
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Affiliation(s)
- Jean Simonnet
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière CRICM, UPMC/INSERM UMR S975/CNRS UMR 7225, CHU Pitié-Salpêtrière, 47 Boulevard de l'Hôpital, 75013, Paris, France
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24
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Sills JB, Connors BW, Burwell RD. Electrophysiological and morphological properties of neurons in layer 5 of the rat postrhinal cortex. Hippocampus 2012; 22:1912-22. [PMID: 22522564 PMCID: PMC3660403 DOI: 10.1002/hipo.22026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2012] [Indexed: 11/11/2022]
Abstract
The postrhinal (POR) cortex of the rat is homologous to the parahippocampal cortex of the primate based on connections and other criteria. POR provides the major visual and visuospatial input to the hippocampal formation, both directly to CA1 and indirectly through connections with the medial entorhinal cortex. Although the cortical and hippocampal connections of the POR cortex are well described, the physiology of POR neurons has not been studied. Here, we examined the electrical and morphological characteristics of layer 5 neurons from POR cortex of 14- to 16-day-old rats using an in vitro slice preparation. Neurons were subjectively classified as regular-spiking (RS), fast-spiking (FS), or low-threshold spiking (LTS) based on their electrophysiological properties and similarities with neurons in other regions of neocortex. Cells stained with biocytin included pyramidal cells and interneurons with bitufted or multipolar dendritic patterns. Similarity analysis using only physiological data yielded three clusters that corresponded to FS, LTS, and RS classes. The cluster corresponding to the FS class was composed entirely of multipolar nonpyramidal cells, and the cluster corresponding to the RS class was composed entirely of pyramidal cells. The third cluster, corresponding to the LTS class, was heterogeneous and included both multipolar and bitufted dendritic arbors as well as one pyramidal cell. We did not observe any intrinsically bursting pyramidal cells, which is similar to entorhinal cortex but unlike perirhinal cortex. We conclude that POR includes at least two major classes of neocortical inhibitory interneurons, but has a functionally restricted cohort of pyramidal cells.
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Affiliation(s)
- Joeseph B. Sills
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | - Barry W. Connors
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | - Rebecca D. Burwell
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
- Department of Cognitive, Linguistic and Psychological Sciences, Brown University, Providence, Rhode Island 02912
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25
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Pilli J, Abbasi S, Richardson M, Kumar SS. Diversity and excitability of deep-layer entorhinal cortical neurons in a model of temporal lobe epilepsy. J Neurophysiol 2012; 108:1724-38. [PMID: 22745466 DOI: 10.1152/jn.00364.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The entorhinal cortex (ERC) is critically implicated in temporal lobe epileptogenesis--the most common type of adult epilepsy. Previous studies have suggested that epileptiform discharges likely initiate in seizure-sensitive deep layers (V-VI) of the medial entorhinal area (MEA) and propagate into seizure-resistant superficial layers (II-III) and hippocampus, establishing a lamina-specific distinction between activities of deep- versus superficial-layer neurons and their seizure susceptibilities. While layer II stellate cells in MEA have been shown to be hyperexcitable and hypersynchronous in patients and animal models of temporal lobe epilepsy (TLE), the fate of neurons in the deep layers under epileptic conditions and their overall contribution to epileptogenicity of this region have remained unclear. We used whole cell recordings from slices of the ERC in normal and pilocarpine-treated epileptic rats to characterize the electrophysiological properties of neurons in this region and directly assess changes in their excitatory and inhibitory synaptic drive under epileptic conditions. We found a surprising heterogeneity with at least three major types and two subtypes of functionally distinct excitatory neurons. However, contrary to expectation, none of the major neuron types characterized showed any significant changes in their excitability, barring loss of excitatory and inhibitory inputs in a subtype of neurons whose dendrite extended into layer III, where neurons are preferentially lost during TLE. We confirmed hyperexcitability of layer II neurons in the same slices, suggesting minimal influence of deep-layer input on superficial-layer neuron excitability under epileptic conditions. These data show that deep layers of ERC contain a more diverse population of excitatory neurons than previously envisaged that appear to belie their seizure-sensitive reputation.
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Affiliation(s)
- Jyotsna Pilli
- Dept. of Biomedical Sciences, College of Medicine, Florida State Univ., 1115 West Call St., Tallahassee, FL 32306-4300, USA
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26
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Canto CB, Witter MP. Cellular properties of principal neurons in the rat entorhinal cortex. I. The lateral entorhinal cortex. Hippocampus 2011; 22:1256-76. [PMID: 22162008 DOI: 10.1002/hipo.20997] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/22/2011] [Indexed: 11/10/2022]
Abstract
The lateral entorhinal cortex (LEC) provides a major cortical input to the hippocampal formation, equaling that of the medial entorhinal cortex (MEC). To understand the functional contributions made by LEC, basic knowledge of individual neurons, in the context of the intrinsic network, is needed. The aim of this study is to compare physiological and morphological properties of principal neurons in different LEC layers in postnatal rats. Using in vitro whole cell current-clamp recordings from up to four post hoc morphologically identified neurons simultaneously, we established that principal neurons show layer specific physiological and morphological properties, similar to those reported previously in adults. Principal neurons in L(ayer) I, LII, and LIII have the majority of their dendrites and axonal collaterals alone in superficial layers. LV contains mainly pyramidal neurons with dendrites and axons extending throughout all layers. A minority of LV and all principal neurons in LVI are neurons with dendrites confined to deep layers and axons in superficial and deep layers. Physiologically, input resistances and time constants of LII neurons are lower and shorter, respectively, than those observed in LV neurons. Fifty-four percent of LII neurons have sag potentials, resonance properties, and rebounds at the offset of hyperpolarizing current injection, whereas LIII and LVI neurons do not have any of these. LV neurons show prominent spike-frequency adaptation and a decrease in spike amplitudes in response to strong depolarization. Despite the well-developed interlaminar communication in LEC, the laminar differences in the biophysical and morphological properties of neurons suggest that their in vivo firing patterns and functions differ, similar to what is known for neurons in different MEC layers.
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Affiliation(s)
- Cathrin B Canto
- Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norwegian University of Science and Technology, Trondheim, Norway
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27
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Canto CB, Witter MP. Cellular properties of principal neurons in the rat entorhinal cortex. II. The medial entorhinal cortex. Hippocampus 2011; 22:1277-99. [PMID: 22161956 DOI: 10.1002/hipo.20993] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2011] [Indexed: 11/05/2022]
Abstract
Principal neurons in different medial entorhinal cortex (MEC) layers show variations in spatial modulation that stabilize between 15 and 30 days postnatally. These in vivo variations are likely due to differences in intrinsic membrane properties and integrative capacities of neurons. The latter depends on inputs and thus potentially on the morphology of principal neurons. In this comprehensive study, we systematically compared the morphological and physiological characteristics of principal neurons in all MEC layers of newborn rats before and after weaning. We recorded simultaneously from up to four post-hoc morphologically identified MEC principal neurons in vitro. Neurons in L(ayer) I-LIII have dendritic and axonal arbors mainly in superficial layers, and LVI neurons mainly in deep layers. The dendritic and axonal trees of part of LV neurons diverge throughout all layers. Physiological properties of principal neurons differ between layers. In LII, most neurons have a prominent sag potential, resonance and membrane oscillations. Neurons in LIII and LVI fire relatively regular, and lack sag potentials and membrane oscillations. LV neurons show the most prominent spike-frequency adaptation and highest input resistance. The data indicate that adult-like principal neuron types can be differentiated early on during postnatal development. The results of the accompanying paper, in which principal neurons in the lateral entorhinal cortex (LEC) were described (Canto and Witter,2011), revealed that significant differences between LEC and MEC exist mainly in LII neurons. We therefore systematically analyzed changes in LII biophysical properties along the mediolateral axis of MEC and LEC. There is a gradient in properties typical for MEC LII neurons. These properties are most pronounced in medially located neurons and become less apparent in more laterally positioned ones. This gradient continues into LEC, such that in LEC medially positioned neurons share some properties with adjacent MEC cells.
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Affiliation(s)
- Cathrin B Canto
- Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norwegian University of Science and Technology, Trondheim, Norway
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28
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Gasparini S. Distance- and activity-dependent modulation of spike back-propagation in layer V pyramidal neurons of the medial entorhinal cortex. J Neurophysiol 2011; 105:1372-9. [PMID: 21209358 DOI: 10.1152/jn.00014.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Layer V principal neurons of the medial entorhinal cortex receive the main hippocampal output and relay processed information to the neocortex. Despite the fundamental role hypothesized for these neurons in memory replay and consolidation, their dendritic features are largely unknown. High-speed confocal and two-photon Ca(2+) imaging coupled with somatic whole cell patch-clamp recordings were used to investigate spike back-propagation in these neurons. The Ca(2+) transient associated with a single back-propagating action potential was considerably smaller at distal dendritic locations (>200 μm from the soma) compared with proximal ones. Perfusion of Ba(2+) (150 μM) or 4-aminopyridine (2 mM) to block A-type K(+) currents significantly increased the amplitude of the distal, but not proximal, Ca(2+) transients, which is strong evidence for an increased density of these channels at distal dendritic locations. In addition, the Ca(2+) transients decreased with each subsequent spike in a 20-Hz train; this activity-dependent decrease was also more prominent at more distal locations and was attenuated by the perfusion of the protein kinase C activator phorbol-di-acetate. These data are consistent with a phosphorylation-dependent control of back-propagation during trains of action potentials, attributable mainly to an increase in the time constant of recovery from voltage-dependent inactivation of dendritic Na(+) channels. In summary, dendritic Na(+) and A-type K(+) channels control spike back-propagation in layer V entorhinal neurons. Because the activity of these channels is highly modulated, the extent of the dendritic Ca(2+) influx is as well, with important functional implications for dendritic integration and associative synaptic plasticity.
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Affiliation(s)
- Sonia Gasparini
- Neuroscience Center, Louisiana State University Health Science Center, 2020 Gravier St., New Orleans, LA 70112, USA.
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29
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Weiss T, Veh RW. Morphological and electrophysiological characteristics of neurons within identified subnuclei of the lateral habenula in rat brain slices. Neuroscience 2010; 172:74-93. [PMID: 20974229 DOI: 10.1016/j.neuroscience.2010.10.047] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 10/15/2010] [Accepted: 10/16/2010] [Indexed: 11/26/2022]
Abstract
Based on the specificity of its inputs and targets, the lateral habenular complex (LHb) constitutes a pivotal motor-limbic interface implicated in various cerebral functions particularly in regulating monoamine transmission. Despite its functional significance, cellular characteristics underlying LHb functionality have not been examined systematically. The present study aimed to correlate morphological and electrophysiological properties of neurons within the different subnuclei of the LHb using whole-cell recording and neurobiotin labeling in rat slice preparations. Morphological analysis revealed a heterogeneous population of projection neurons randomly distributed throughout the LHb. According to somatodendritic characteristics four main categories were classified including spherical, fusiform, polymorphic and vertical cells. Electrophysiological characterization of neurons within the different categories demonstrated homologous profiles and no significant differences between groups. Typically, LHb neurons possessed high input resistances and long membrane time constants. They also displayed time-dependent inward rectification and distinct afterhyperpolarization. A salient electrophysiological feature of LHb neurons was their ability to generate rebound bursts of action potentials in response to membrane hyperpolarization. Based on the pattern of spontaneous activity, neurons were classified as silent, tonic or bursting. The occurrence of distinctive firing modes was not related to topographic allocation. The patterns of spontaneous firing and evoked discharge were highly sensitive to alterations in membrane potential and merged upon de- and hyperpolarizing current injection and synaptic stimulation. Besides projection neurons, recordings revealed the existence of a subpopulation of cells possessing morphological and physiological properties of neocortical neurogliaform cells. They were considered to be interneurons. Our data suggest that neurons within the different LHb subnuclei behave electrophysiologically more similar than expected, considering their morphological heterogeneity. We conclude that the formation of functional neuronal entities within the LHb may be achieved through defined synaptic inputs to particular neurons, rather than by individual neuronal morphologies and intrinsic membrane properties.
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Affiliation(s)
- T Weiss
- Institut für Integrative Neuroanatomie, Centrum für Anatomie, Charité—Universitätsmedizin Berlin, Berlin, Germany.
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Gatome CW, Slomianka L, Mwangi DK, Lipp HP, Amrein I. The entorhinal cortex of the Megachiroptera: a comparative study of Wahlberg’s epauletted fruit bat and the straw-coloured fruit bat. Brain Struct Funct 2010; 214:375-93. [DOI: 10.1007/s00429-010-0239-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Accepted: 01/09/2010] [Indexed: 10/19/2022]
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Bragin DE, Sanderson JL, Peterson S, Connor JA, Müller WS. Development of epileptiform excitability in the deep entorhinal cortex after status epilepticus. Eur J Neurosci 2009; 30:611-24. [PMID: 19674083 PMCID: PMC2776653 DOI: 10.1111/j.1460-9568.2009.06863.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Epileptiform neuronal activity during seizures is observed in many brain areas, but its origins following status epilepticus (SE) are unclear. We have used the Li low-dose pilocarpine rat model of temporal lobe epilepsy to examine early development of epileptiform activity in the deep entorhinal cortex (EC). We show that during the 3-week latent period that follows SE, an increasing percentage of neurons in EC layer 5 respond to a single synaptic stimulus with polysynaptic burst depolarizations. This change is paralleled by a progressive depolarizing shift of the inhibitory postsynaptic potential reversal potential in layer 5 neurons, apparently caused by upregulation of the Cl(-) inward transporter NKCC1 and concurrent downregulation of the Cl(-) outward transporter KCC2, both changes favoring intracellular Cl(-) accumulation. Inhibiting Cl(-) uptake in the latent period restored more negative GABAergic reversal potentials and eliminated polysynaptic bursts. The changes in the Cl(-) transporters were highly specific to the deep EC. They did not occur in layers 1-3, perirhinal cortex, subiculum or dentate gyrus during this period. We propose that the changes in Cl(-) homeostasis facilitate hyperexcitability in the deep entorhinal cortex leading to epileptiform discharge there, which subsequently affects downstream cortical regions.
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Affiliation(s)
- Denis E Bragin
- Department of Neurosurgery, University of New Mexico School of Medicine, University of New Mexico, Albuquerque, NM, USA
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Neuronal classes in the corticoid complex of the telencephalon of the strawberry finch, Estrilda amandava. Cell Tissue Res 2009; 336:393-409. [DOI: 10.1007/s00441-009-0790-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2008] [Accepted: 03/05/2009] [Indexed: 10/20/2022]
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What does the anatomical organization of the entorhinal cortex tell us? Neural Plast 2009; 2008:381243. [PMID: 18769556 PMCID: PMC2526269 DOI: 10.1155/2008/381243] [Citation(s) in RCA: 263] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 05/23/2008] [Indexed: 12/28/2022] Open
Abstract
The entorhinal cortex is commonly perceived as a major input and output structure of the hippocampal formation, entertaining the role of the nodal point of cortico-hippocampal circuits. Superficial layers receive convergent cortical information, which is relayed to structures in the hippocampus, and hippocampal output reaches deep layers of entorhinal cortex, that project back to the cortex. The finding of the grid cells in all layers and reports on interactions between deep and superficial layers indicate that this rather simplistic perception may be at fault. Therefore, an integrative approach on the entorhinal cortex, that takes into account recent additions to our knowledge database on entorhinal connectivity, is timely. We argue that layers in entorhinal cortex show different functional characteristics most likely not on the basis of strikingly different inputs or outputs, but much more likely on the basis of differences in intrinsic organization, combined with very specific sets of inputs. Here, we aim to summarize recent anatomical data supporting the notion that the traditional description of the entorhinal cortex as a layered input-output structure for the hippocampal formation does not give the deserved credit to what this structure might be contributing to the overall functions of cortico-hippocampal networks.
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Abstract
The oscillatory interference model [Burgess et al. (2007) Hippocampus 17:801-802] of grid cell firing is reviewed as an algorithmic level description of path integration and as an implementation level description of grid cells and their inputs. New analyses concern the relationships between the variables in the model and the theta rhythm, running speed, and the intrinsic firing frequencies of grid cells. New simulations concern the implementation of velocity-controlled oscillators (VCOs) with different preferred directions in different neurons. To summarize the model, the distance traveled along a specific direction is encoded by the phase of a VCO relative to a baseline frequency. Each VCO is an intrinsic membrane potential oscillation whose frequency increases from baseline as a result of depolarization by synaptic input from speed modulated head-direction cells. Grid cell firing is driven by the VCOs whose preferred directions match the current direction of motion. VCOs are phase-reset by location-specific input from place cells to prevent accumulation of error. The baseline frequency is identified with the local average of VCO frequencies, while EEG theta frequency is identified with the global average VCO frequency and comprises two components: the frequency at zero speed and a linear response to running speed. Quantitative predictions are given for the inter-relationships between a grid cell's intrinsic firing frequency and grid scale, the two components of theta frequency, and the running speed of the animal. Qualitative predictions are given for the properties of the VCOs, and the relationship between environmental novelty, the two components of theta, grid scale and place cell remapping.
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Affiliation(s)
- Neil Burgess
- Institute of Cognitive Neuroscience, University College London.
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35
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Glasgow SD, Chapman CA. Conductances mediating intrinsic theta-frequency membrane potential oscillations in layer II parasubicular neurons. J Neurophysiol 2008; 100:2746-56. [PMID: 18815347 DOI: 10.1152/jn.90351.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ionic conductances that generate membrane potential oscillations in neurons of layer II of the parasubiculum were studied using whole cell current-clamp recordings in horizontal slices from the rat brain. Blockade of ionotropic glutamate and GABA synaptic transmission did not reduce the power of the oscillations, indicating that oscillations are not dependent on synaptic inputs. Oscillations were eliminated when cells were hyperpolarized 6-10 mV below spike threshold, indicating that they are mediated by voltage-dependent conductances. Application of TTX completely eliminated oscillations, suggesting that Na(+) currents are required for the generation of the oscillations. Oscillations were not reduced by blocking Ca(2+) currents with Cd(2+) or Ca(2+)-free artificial cerebrospinal fluid, or by blocking K(+) conductances with either 50 microM or 5 mM 4-aminopyridine (4-AP), 30 mM tetraethylammonium (TEA), or Ba(2+)(1-2 mM). Oscillations also persisted during blockade of the muscarinic-dependent K(+) current, I(M), using the selective antagonist XE-991 (10 microM). However, oscillations were significantly attenuated by blocking the hyperpolarization-activated cationic current I(h) with Cs(+) and were almost completely blocked by the more potent I(h) blocker ZD7288 (100 microM). Intrinsic membrane potential oscillations in neurons of layer II of the parasubiculum are therefore likely driven by an interaction between an inward persistent Na(+) current and time-dependent deactivation of I(h). These voltage-dependent conductances provide a mechanism for the generation of membrane potential oscillations that can help support rhythmic network activity within the parasubiculum during theta-related behaviors.
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Affiliation(s)
- Stephen D Glasgow
- Ctr. for Studies in Behavioral Neurobiology, Dept. of Psychology, Concordia Univ., 7141 Sherbrooke St. W., Rm. SP-244, Montréal, Québec, Canada H4B 1R6
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Hafting T, Fyhn M, Bonnevie T, Moser MB, Moser EI. Hippocampus-independent phase precession in entorhinal grid cells. Nature 2008; 453:1248-52. [PMID: 18480753 DOI: 10.1038/nature06957] [Citation(s) in RCA: 321] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Accepted: 04/01/2008] [Indexed: 11/09/2022]
Abstract
Theta-phase precession in hippocampal place cells is one of the best-studied experimental models of temporal coding in the brain. Theta-phase precession is a change in spike timing in which the place cell fires at progressively earlier phases of the extracellular theta rhythm as the animal crosses the spatially restricted firing field of the neuron. Within individual theta cycles, this phase advance results in a compressed replication of the firing sequence of consecutively activated place cells along the animal's trajectory, at a timescale short enough to enable spike-time-dependent plasticity between neurons in different parts of the sequence. The neuronal circuitry required for phase precession has not yet been established. The fact that phase precession can be seen in hippocampal output stuctures such as the prefrontal cortex suggests either that efferent structures inherit the precession from the hippocampus or that it is generated locally in those structures. Here we show that phase precession is expressed independently of the hippocampus in spatially modulated grid cells in layer II of medial entorhinal cortex, one synapse upstream of the hippocampus. Phase precession is apparent in nearly all principal cells in layer II but only sparsely in layer III. The precession in layer II is not blocked by inactivation of the hippocampus, suggesting that the phase advance is generated in the grid cell network. The results point to possible mechanisms for grid formation and raise the possibility that hippocampal phase precession is inherited from entorhinal cortex.
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Affiliation(s)
- Torkel Hafting
- Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norwegian University of Science and Technology, NO-7489 Trondheim, Norway
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de Guzman P, Inaba Y, Baldelli E, de Curtis M, Biagini G, Avoli M. Network hyperexcitability within the deep layers of the pilocarpine-treated rat entorhinal cortex. J Physiol 2008; 586:1867-83. [PMID: 18238812 DOI: 10.1113/jphysiol.2007.146159] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In this study we report that in the presence of normal buffer, epileptiform discharges occur spontaneously (duration = 2.60 +/- 0.49 s) or can be induced by electrical stimuli (duration = 2.50 +/- 0.62 s) in the entorhinal cortex (EC) of brain slices obtained from pilocarpine-treated rats but not in those from age-matched, nonepileptic control (NEC) animals. These network-driven epileptiform events consist of field oscillatory sequences at frequencies greater than 200 Hz that most often initiate in the lateral EC and propagate to the medial EC with 4-63 ms delays. The NMDA receptor antagonist CPP depresses the rate of occurrence (P < 0.01) of these spontaneous epileptiform discharges but fails in blocking them. Paradoxically, stimulus-induced epileptiform responses are enhanced in duration during CPP application. However, concomitant application of NMDA and non-NMDA glutamatergic antagonists abolishes spontaneous and stimulus-induced epileptiform events. Intracellular recordings from lateral EC layer V cells indicate a lower frequency of spontaneous hyperpolarizing postsynaptic potentials in pilocarpine-treated tissue than in NEC (P < 0.002) both under control conditions and with glutamatergic receptor blockade; the reversal potential of pharmacologically isolated GABA(A) receptor-mediated inhibitory postsynaptic potentials has similar values in the two types of tissue. Finally, immunohistochemical analysis shows that parvalbumin-positive interneurons are selectively reduced in number in EC deep layers. Collectively, these results indicate that reduced inhibition within the pilocarpine-treated EC layer V may promote network epileptic hyperexcitability.
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Affiliation(s)
- Philip de Guzman
- Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, Montreal, QC H3A 2B4, Canada
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Yoshida M, Alonso A. Cell-type specific modulation of intrinsic firing properties and subthreshold membrane oscillations by the M(Kv7)-current in neurons of the entorhinal cortex. J Neurophysiol 2007; 98:2779-94. [PMID: 17728392 DOI: 10.1152/jn.00033.2007] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The M-current (current through Kv7 channels) is a low-threshold noninactivating potassium current that is suppressed by muscarinic agonists. Recent studies have shown its role in spike burst generation and intrinsic subthreshold theta resonance, both of which are important for memory function. However, little is known about its role in principal cells of the entorhinal cortex (EC). In this study, using whole cell patch recording techniques in a rat EC slice preparation, we have examined the effects of the M-current blockers linopirdine and XE991 on the membrane dynamics of principal cells in the EC. When the M-current was blocked, layer II nonstellate cells (non-SCs) and layer III cells switched from tonic discharge to intermittent firing mode, during which layer II non-SCs showed high-frequency short-duration spike bursts due to increased fast spike afterdepolarization (ADP). When three spikes were elicited at 50 Hz, these two types of cells reacted with a slow ADP that drove delayed firing. In contrast, layer II stellate cells (SCs) and layer V cells never displayed intermittent firing, bursting behavior, or delayed firing. Under the M-current block, intrinsic excitability increased significantly in layer III and layer V cells but not in layer II SCs and non-SCs. The M-current block also had contrasting effects on the subthreshold excitability, greatly suppressing the subthreshold membrane potential oscillations in layer V cells but not in layer II SCs. Modulation of the M-current thus shifts the firing behavior, intrinsic excitability, and subthreshold membrane potential oscillations of EC principal cells in a cell-type-dependent manner.
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Affiliation(s)
- Motoharu Yoshida
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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39
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Gnatkovsky V, Wendling F, de Curtis M. Cellular correlates of spontaneous periodic events in the medial entorhinal cortex of the in vitro isolated guinea pig brain. Eur J Neurosci 2007; 26:302-11. [PMID: 17650108 DOI: 10.1111/j.1460-9568.2007.05667.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Periodic potentials characterized by fast oscillations superimposed on a slow complex event are typically observed in cortical structures during sleep and anaesthesia. In the entorhinal cortex (EC) similar spontaneous periodic events (SPEs) have been described both in vivo and in vitro. Simultaneous extracellular and intracellular recordings from superficial neurons of the entorhinal cortex of the isolated Hartley guinea pig brain preparation demonstrated that SPEs recur with a periodicity of 2-10 s and correlate to neuronal firing superimposed on a depolarizing plateau that lasts 0.7-1 s. During SPEs, putative interneurons in all layers discharged high frequency firing (> 100 Hz), whereas no activity was observed in principal neurons of deep entorhinal cortex layers. Linear correlation analysis demonstrated a tight relationship between the fast component of the extracellular SPE and subthreshold oscillatory activity/neuronal firing in both superficial neurons and putative interneurons; firing of deep principal cells was independent from SPEs occurrence. The present study demonstrates that recurrent spontaneous events analogous to periodic activity observed during sleep/anaesthesia are generated in the entorhinal cortex by the interactions between superficial neurons and interneurons.
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Affiliation(s)
- Vadym Gnatkovsky
- Department of Experimental Neurophysiology, Fondazione Istituto Neurologico, via Celoria 11, 20133 Milan, Italy
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Labyt E, Frogerais P, Uva L, Bellanger JJ, Wendling F. Modeling of Entorhinal Cortex and Simulation of Epileptic Activity: Insights Into the Role of Inhibition-Related Parameters. ACTA ACUST UNITED AC 2007; 11:450-61. [PMID: 17674628 PMCID: PMC2230631 DOI: 10.1109/titb.2006.889680] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper describes a macroscopic neurophysiologically relevant model of the entorhinal cortex (EC), a brain structure largely involved in human mesio-temporal lobe epilepsy. This model is intervalidated in the experimental framework of ictogenesis animal model (isolated guinea-pig brain perfused with bicuculline). Using sensitivity and stability analysis, an investigation of model parameters related to GABA neurotransmission (recognized to be involved in epileptic activity generation) was performed. Based on spectral and statistical features, simulated signals generated from the model for multiple GABAergic inhibition-related parameter values were classified into eight classes of activity. Simulated activities showed striking agreement (in terms of realism) with typical epileptic activities identified in field potential recordings performed in the experimental model. From this combined computational/experimental approach, hypotheses are suggested about the role of different types of GABAergic neurotransmission in the generation of epileptic activities in EC.
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Affiliation(s)
- Etienne Labyt
- Inserm U642, Laboratoire Traitement du Signal et de L'Image, University of Rennes 1, 35042 Rennes, France.
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41
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Castelli L, Nigro MJ, Magistretti J. Analysis of resurgent sodium-current expression in rat parahippocampal cortices and hippocampal formation. Brain Res 2007; 1163:44-55. [PMID: 17628510 DOI: 10.1016/j.brainres.2007.05.065] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Revised: 05/08/2007] [Accepted: 05/10/2007] [Indexed: 11/12/2022]
Abstract
The resurgent Na(+) current (I(NaR)) is a component of neuronal voltage-dependent Na(+) currents that is activated by repolarization and is believed to result from an atypical path of Na(+)-channel recovery from inactivation. So far, I(NaR) has only been identified in a small number of central neuronal populations in the cerebellum, diencephalon, and brainstem. The possible presence and roles of I(NaR) in neurons of the cerebral cortex and temporal-lobe memory system are still uncharacterized. In this study whole-cell, patch-clamp experiments were carried out in acute rat brain slices to investigate I(NaR) expression and properties in several neuronal populations of the parahippocampal region and hippocampal formation. Specifically, we examined pyramidal neurons of perirhinal cortex areas 36 and 35 (layers II and V); neurons of superficial and deep layers of medial entorhinal cortex (mEC); dentate gyrus (DG) granule cells; and pyramidal cells of the CA3 and CA1 hippocampal fields. I(NaR) was found to be thoroughly expressed in parahippocampal cortices. The most consistent and prominent I(NaR) expression was observed in mEC layer-II cells. A vast majority of areas 36 and 35 neurons (both in layers II and V) and mEC layer-III and -V neurons were also endowed with I(NaR), although at lower amplitude levels. I(NaR) was expressed by approximately 60% of DG granule cells and approximately 35% of CA1 pyramidal cells of the ventral hippocampus, whereas it was never observed in CA3 neurons (both in the ventral and dorsal hippocampus) and CA1 neurons of the dorsal hippocampus. The biophysical properties of I(NaR) were very similar in all of the neuronal types in which the current was observed, with a peak in the current-voltage relationship at -35/-40 mV. Our results show that the parahippocampal region and part of the hippocampal formation are sites of major I(NaR) expression, and provide a new basis for further studies on the molecular correlates of I(NaR).
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Affiliation(s)
- Loretta Castelli
- Dipartimento di Scienze Fisiologiche-Farmacologiche Cellulari-Molecolari, Sezione di Fisiologia Generale e Biofisica Cellulare, Università degli Studi di Pavia, Via Forlanini 6, 27100 Pavia, Italy
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42
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Ma L, Shalinsky MH, Alonso A, Dickson CT. Effects of serotonin on the intrinsic membrane properties of layer II medial entorhinal cortex neurons. Hippocampus 2007; 17:114-29. [PMID: 17146777 DOI: 10.1002/hipo.20250] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although serotonin (5-HT) is an important neuromodulator in the superficial layers of the medial entorhinal cortex (mEC), there is some disagreement concerning its influences upon the membrane properties of neurons within this region. We performed whole cell recordings of mEC Layer II projection neurons in rat brain slices in order to characterize the intrinsic influences of 5-HT. In current clamp, 5-HT evoked a biphasic response consisting of a moderately short latency and large amplitude hyperpolarization followed by a slowly developing, long lasting, and small amplitude depolarization. Correspondingly, in voltage clamp, 5-HT evoked a robust outward followed by a smaller inward shift of holding current. The outward current evoked by 5-HT showed a consistent current/voltage (I/V) relationship across cells with inward rectification, and demonstrating a reversal potential that was systematically dependent upon the extracellular concentration of K(+), suggesting that it was predominantly carried by potassium ions. However, the inward current showed a less consistent I/V relationship across different cells, suggesting multiple independent ionic mechanisms. The outward current was mediated through activation of 5-HT(1A) receptors via a G-protein dependent mechanism while inward currents were evoked in a 5-HT(1A)-independent fashion. A significant proportion of the inward current was blocked by the I(h) inhibitor ZD7288 and appeared to be due to 5-HT modulation of I(h) as 5-HT shifted the activation curve of I(h) in a depolarizing fashion. Serotonin is thus likely to influence, in a composite fashion, the information processing of Layer II neurons in the mEC and thus, the passage of neocortical information via the perforant pathway to the hippocampus.
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Affiliation(s)
- Li Ma
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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43
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Egorov AV, Unsicker K, von Bohlen und Halbach O. Muscarinic control of graded persistent activity in lateral amygdala neurons. Eur J Neurosci 2007; 24:3183-94. [PMID: 17156379 DOI: 10.1111/j.1460-9568.2006.05200.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cholinergic system is crucially involved in several cognitive processes including attention, learning and memory. Muscarinic actions have profound effects on the intrinsic firing pattern of neurons. In principal neurons of the entorhinal cortex (EC), muscarinic receptors activate an intrinsic cation current that causes multiple self-sustained spiking activity, which represents a potential mechanism for transiently sustaining information about novel items. The amygdala appears to be important for experience-dependent learning by emotional arousal, and cholinergic muscarinic influences are essential for the amygdala-mediated modulation of memory. Here we show that principal neurons from the lateral nucleus of the amygdala (LA) can generate intrinsic graded persistent activity that is similar to EC layer V cells. This firing behavior is linked to muscarinic activation of a calcium-sensitive non-specific cation current and can be mimicked by stimulation of cholinergic afferents that originate from the nucleus basalis of Meynert (n. M). Moreover, we demonstrate that the projections from the n. M. are essential and sufficient for the control and modulation of graded firing activity in LA neurons. We found that activation of these cholinergic afferents (i) is required to maintain and to increase firing rates in a graded manner, and (ii) is sufficient for the graded increases of stable discharge rates even without an associated up-regulation of Ca2+. The induction of persistent activity was blocked by flufenamic acid or 2-APB and remained intact after Ca2+-store depletion with thapsigargin. The internal ability of LA neurons to generate graded persistent activity could be essential for amygdala-mediated memory operations.
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Affiliation(s)
- Alexei V Egorov
- Interdisciplinary Center for Neurosciences (IZN), Department of Neuroanatomy, University of Heidelberg, Im Neuenheimer Feld 307, D-69120 Heidelberg, Germany.
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44
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Furtak SC, Moyer JR, Brown TH. Morphology and ontogeny of rat perirhinal cortical neurons. J Comp Neurol 2007; 505:493-510. [DOI: 10.1002/cne.21516] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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45
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Witter MP, Moser EI. Spatial representation and the architecture of the entorhinal cortex. Trends Neurosci 2006; 29:671-8. [PMID: 17069897 DOI: 10.1016/j.tins.2006.10.003] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 09/28/2006] [Accepted: 10/12/2006] [Indexed: 12/01/2022]
Abstract
It has recently been recognized that the entorhinal cortex has a crucial role in spatial representation and navigation. How the position of an animal is computed within the entorhinal circuitry remains to be determined, but the architectural organization of this brain area might provide some clues. Here, we review three organizational principles--recurrent connectivity, interlaminar connectivity and modular organization--and propose how each of them might contribute to the emergence and maintenance of positional representations in entorhinal neural networks.
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Affiliation(s)
- Menno P Witter
- Research Institute Neurosciences, Department of Anatomy and Neurosciences, VU University Medical Center, Amsterdam, The Netherlands.
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46
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McNaughton BL, Battaglia FP, Jensen O, Moser EI, Moser MB. Path integration and the neural basis of the 'cognitive map'. Nat Rev Neurosci 2006; 7:663-78. [PMID: 16858394 DOI: 10.1038/nrn1932] [Citation(s) in RCA: 1139] [Impact Index Per Article: 63.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The hippocampal formation can encode relative spatial location, without reference to external cues, by the integration of linear and angular self-motion (path integration). Theoretical studies, in conjunction with recent empirical discoveries, suggest that the medial entorhinal cortex (MEC) might perform some of the essential underlying computations by means of a unique, periodic synaptic matrix that could be self-organized in early development through a simple, symmetry-breaking operation. The scale at which space is represented increases systematically along the dorsoventral axis in both the hippocampus and the MEC, apparently because of systematic variation in the gain of a movement-speed signal. Convergence of spatially periodic input at multiple scales, from so-called grid cells in the entorhinal cortex, might result in non-periodic spatial firing patterns (place fields) in the hippocampus.
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Affiliation(s)
- Bruce L McNaughton
- Arizona Research Laboratories Division of Neural Systems, Memory & Aging, and Department of Psychology, University of Arizona, Tucson 85724, USA.
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47
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Woźnicka A, Malinowska M, Kosmal A. Cytoarchitectonic organization of the entorhinal cortex of the canine brain. ACTA ACUST UNITED AC 2006; 52:346-67. [PMID: 16787665 DOI: 10.1016/j.brainresrev.2006.04.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Revised: 04/26/2006] [Accepted: 04/28/2006] [Indexed: 11/26/2022]
Abstract
The present study describes the cytoarchitectonic and chemoarchitectonic organization of the canine entorhinal cortex (EC). We distinguished medial, laterodorsal, and latero-intermediate subdivisions based on the organization of cortical layers using Nissl and Timm staining and AChE histochemistry. The medial subdivision is located at the border of the parasubiculum and is characterized by a narrow cortex, wide layer II, and densely packed cells in layer V. At its caudal extent, distinct spherical groups of small cells are situated at the border of layer I/II. The laterodorsal subdivision is located along the rhinal sulcus and borders area 35 of the perirhinal cortex. Its cortex is wide and layers tend to merge. Layer II of the laterodorsal subdivision contains scattered "stellate" cells, which are not organized into islands. The latero-intermediate subdivision displays a complex layer organization. The most easily distinguished is layer II, which is comprised of two main cell populations; "stellate" neurons arranged into "islands" and small, round cells distributed within and below the stellate cells. Layer III contains sparse cells that are arranged into vertical clusters, whereas layer IV (lamina dissecans) is especially wide. Nine fields, named according to their rostral to caudal position, were distinguished based on further analyses of layer differentiation. The main features of the rostrocaudal differentiation are a gradual disappearance of "island" organization in layer II, increasing cortical thickness, and wider layers containing small and more densely packed cells. Cytoarchitectonic differentiation was determined by observation of specific histochemical patterns of AChE- and Timm-stained sections.
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Affiliation(s)
- Agnieszka Woźnicka
- Department of Neurophysiology, Nencki Institute of Experimental Biology, 3 Pasteur Str., 02-093 Warsaw, Poland
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Sargolini F, Fyhn M, Hafting T, McNaughton BL, Witter MP, Moser MB, Moser EI. Conjunctive representation of position, direction, and velocity in entorhinal cortex. Science 2006; 312:758-62. [PMID: 16675704 DOI: 10.1126/science.1125572] [Citation(s) in RCA: 859] [Impact Index Per Article: 47.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Grid cells in the medial entorhinal cortex (MEC) are part of an environment-independent spatial coordinate system. To determine how information about location, direction, and distance is integrated in the grid-cell network, we recorded from each principal cell layer of MEC in rats that explored two-dimensional environments. Whereas layer II was predominated by grid cells, grid cells colocalized with head-direction cells and conjunctive grid x head-direction cells in the deeper layers. All cell types were modulated by running speed. The conjunction of positional, directional, and translational information in a single MEC cell type may enable grid coordinates to be updated during self-motion-based navigation.
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Affiliation(s)
- Francesca Sargolini
- Centre for the Biology of Memory, Norwegian University of Science and Technology, 7489 Trondheim, Norway
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Labyt E, Uva L, De Curtis M, Wendling F. Realistic modeling of entorhinal cortex field potentials and interpretation of epileptic activity in the guinea pig isolated brain preparation. J Neurophysiol 2006; 96:363-77. [PMID: 16598061 PMCID: PMC2486351 DOI: 10.1152/jn.01342.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanisms underlying epileptic activities recorded from entorhinal cortex (EC) were studied through a computational model based on review of cytoarchitectonic and neurobiological data about this structure. The purpose of this study is to describe and use this model to interpret epileptiform discharge patterns recorded in an experimental model of ictogenesis (guinea pig isolated brain perfused with bicuculline). A macroscopic modeling approach representing synaptic interactions between cells subpopulations in the EC was chosen for its adequacy to mimic field potentials reflecting overall dynamics rising from interconnected cells populations. Therefore intrinsic properties of neurons were not included in the modeling design. Model parameters were adjusted from an identification procedure based on quantitative comparison between real and simulated signals. For both EC deep and superficial layers, results show that the model generates very realistic signals regarding temporal dynamics, spectral features, and cross-correlation values. These simulations allowed us to infer information about the evolution of synaptic transmission between principal cell and interneuronal populations and about connectivity between deep and superficial layers during the transition from background to ictal activity. In the model, this transition was obtained for increased excitation in deep versus superficial layers. Transitions between epileptiform activities [interictal spikes, fast onset activity (25 Hz), ictal bursting activity] were explained by changes of parameters mainly related to GABAergic interactions. Notably, the model predicted an important role of GABAa,fast- and GABAb-receptor-mediated inhibition in the generation of ictal fast onset and burst activities, respectively. These findings are discussed with respect to experimental data.
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Affiliation(s)
- Etienne Labyt
- LTSI, Laboratoire Traitement du Signal et de l'Image
INSERM : U642Université Rennes ICampus de Beaulieu,
263 Avenue du Général Leclerc - CS 74205 - 35042 Rennes Cedex,FR
| | - Laura Uva
- Department Experimental Neurophysiology
Istituto Nazionale Neurologico C. Bestavia Celoria 11
20133 Milan,IT
| | - Marco De Curtis
- Department Experimental Neurophysiology
Istituto Nazionale Neurologico C. Bestavia Celoria 11
20133 Milan,IT
| | - Fabrice Wendling
- LTSI, Laboratoire Traitement du Signal et de l'Image
INSERM : U642Université Rennes ICampus de Beaulieu,
263 Avenue du Général Leclerc - CS 74205 - 35042 Rennes Cedex,FR
- * Correspondence should be adressed to: Fabrice Wendling
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Tahvildari B, Alonso A. Morphological and electrophysiological properties of lateral entorhinal cortex layers II and III principal neurons. J Comp Neurol 2006; 491:123-40. [PMID: 16127693 DOI: 10.1002/cne.20706] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The intrinsic electrophysiology and morphology of neurons from layers II and III of the lateral entorhinal cortex (EC) was investigated in a rat brain slice preparation by intracellular recording and biocytin labeling. Morphologically, we distinguished three groups of layer II principal neurons. The most numerous group included cells with multiple radiating dendrites that spread over layers II and I in a fan-like fashion. While morphologically "fan" neurons were similar to the "stellate" cells of the medial EC, electrophysiologically the fan cells lacked the persistent rhythmic subthreshold oscillations and the very pronounced time-dependent inward rectification typical of the stellate cells. The second group consisted of pyramidal cells that manifested regular spike firing and had a more negative resting potential and a longer spike duration than the fan cells. In the third group we included all those neurons that had diverse multipolar appearances distinct from the fan cells. Neurons in this group had electrophysiological profiles intermediate between those of the fan and pyramidal cells. All neurons recorded in layer III were pyramidal in shape with a basal dendritic tree that could extend into layer V and an axon that could also give off collaterals into layer V. Electrophysiologically, layer III pyramidal cells were very similar to those of layer II. On the basis of these and other data we suggest that in different EC regions layer II neurons may be conducting more input-dependent specialized processing, while cells from layer III may perform a more global or generalized function.
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Affiliation(s)
- Babak Tahvildari
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada.
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