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Ledderose JMT, Zolnik TA, Toumazou M, Trimbuch T, Rosenmund C, Eickholt BJ, Jaeger D, Larkum ME, Sachdev RNS. Layer 1 of somatosensory cortex: an important site for input to a tiny cortical compartment. Cereb Cortex 2023; 33:11354-11372. [PMID: 37851709 PMCID: PMC10690867 DOI: 10.1093/cercor/bhad371] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 09/17/2023] [Indexed: 10/20/2023] Open
Abstract
Neocortical layer 1 has been proposed to be at the center for top-down and bottom-up integration. It is a locus for interactions between long-range inputs, layer 1 interneurons, and apical tuft dendrites of pyramidal neurons. While input to layer 1 has been studied intensively, the level and effect of input to this layer has still not been completely characterized. Here we examined the input to layer 1 of mouse somatosensory cortex with retrograde tracing and optogenetics. Our assays reveal that local input to layer 1 is predominantly from layers 2/3 and 5 pyramidal neurons and interneurons, and that subtypes of local layers 5 and 6b neurons project to layer 1 with different probabilities. Long-range input from sensory-motor cortices to layer 1 of somatosensory cortex arose predominantly from layers 2/3 neurons. Our optogenetic experiments showed that intra-telencephalic layer 5 pyramidal neurons drive layer 1 interneurons but have no effect locally on layer 5 apical tuft dendrites. Dual retrograde tracing revealed that a fraction of local and long-range neurons was both presynaptic to layer 5 neurons and projected to layer 1. Our work highlights the prominent role of local inputs to layer 1 and shows the potential for complex interactions between long-range and local inputs, which are both in position to modify the output of somatosensory cortex.
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Affiliation(s)
- Julia M T Ledderose
- Institute of Biology, Humboldt Universität zu Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
- Institute of Molecular Biology and Biochemistry, Charité—Universitätsmedizin Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
| | - Timothy A Zolnik
- Institute of Biology, Humboldt Universität zu Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
- Institute of Molecular Biology and Biochemistry, Charité—Universitätsmedizin Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
| | - Maria Toumazou
- Institute of Biology, Humboldt Universität zu Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
| | - Thorsten Trimbuch
- Institute of Neurophysiology, Charité—Universitätsmedizin Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
| | - Christian Rosenmund
- Institute of Neurophysiology, Charité—Universitätsmedizin Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
- Neurocure Centre for Excellence Charité—Universitätsmedizin Berlin Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
| | | | - Dieter Jaeger
- Department of Biology, Emory University, Atlanta, GA 30322, USA
| | - Matthew E Larkum
- Institute of Biology, Humboldt Universität zu Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
- Neurocure Centre for Excellence Charité—Universitätsmedizin Berlin Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
| | - Robert N S Sachdev
- Institute of Biology, Humboldt Universität zu Berlin, Charitéplatz 1, Virchowweg 6, 10117 Berlin, Germany
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Li Z, Li Z, Xu W, Li Y, Wang Q, Xu H, Manyande A, Wu D, Feng M, Xiang H. The connectome from the cerebral cortex to the viscera using viral transneuronal tracers. Am J Transl Res 2021; 13:12152-12167. [PMID: 34956443 PMCID: PMC8661218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 09/12/2021] [Indexed: 06/14/2023]
Abstract
As an emerging framework in neuroscience, brain connectomics is well suited for investigating key questions on brain complexity by combining viral transneuronal tracing and whole brain graphic methodologies using analytical tools of network science. Transsynaptic viral tract-tracing in the toolbox of neural labeling methods has been a significant development in the connectomics field to decipher the circuit-level architecture of the cerebral cortex. In the present work, we reviewed the current methods enabling structural connectivity from the viscera to the cerebral cortex mapping with viral transneuronal tracers and showed how such neuroanatomic connectomic data could be used to infer new structural and functional information in viscera-cerebral cortex circuits.
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Affiliation(s)
- Zhixiao Li
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
| | - Zhen Li
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
| | - Weiguo Xu
- Department of Orthopedics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, China
| | - Yujuan Li
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
| | - Qian Wang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
| | - Hui Xu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
| | - Anne Manyande
- School of Human and Social Sciences, University of West LondonLondon W5 2NU, UK
| | - Duozhi Wu
- Department of Anesthesiology, People’s Hospital of Hainan ProvinceHaikou 570311, Hainan, China
| | - Maohui Feng
- Department of Gastrointestinal Surgery, Wuhan Peritoneal Cancer Clinical Medical Research Center, Zhongnan Hospital of Wuhan University, Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study CenterWuhan 430071, Hubei, China
| | - Hongbing Xiang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
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3
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Henrich MT, Geibl FF, Lakshminarasimhan H, Stegmann A, Giasson BI, Mao X, Dawson VL, Dawson TM, Oertel WH, Surmeier DJ. Determinants of seeding and spreading of α-synuclein pathology in the brain. SCIENCE ADVANCES 2020; 6:eabc2487. [PMID: 33177086 PMCID: PMC7673735 DOI: 10.1126/sciadv.abc2487] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 09/22/2020] [Indexed: 05/22/2023]
Abstract
In Parkinson's disease (PD), fibrillar forms of α-synuclein are hypothesized to propagate through synaptically coupled networks, causing Lewy pathology (LP) and neurodegeneration. To more rigorously characterize the determinants of spreading, preformed α-synuclein fibrils were injected into the mouse pedunculopontine nucleus (PPN), a brain region that manifests LP in PD patients and the distribution of developing α-synuclein pathology compared to that ascertained by anterograde and retrograde connectomic mapping. Within the PPN, α-synuclein pathology was cell-specific, being robust in PD-vulnerable cholinergic neurons but not in neighboring noncholinergic neurons. While nearly all neurons projecting to PPN cholinergics manifested α-synuclein pathology, the kinetics, magnitude, and persistence of the propagated pathology were unrelated to the strength of those connections. Thus, neuronal phenotype governs the somatodendritic uptake of pathological α-synuclein, and while the afferent connectome restricts the subsequent spreading of pathology, its magnitude and persistence is not a strict function of the strength of coupling.
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Affiliation(s)
- Martin T Henrich
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Department of Neurology, Philipps University Marburg, Marburg 35043, Germany
| | - Fanni F Geibl
- Department of Neurology, Philipps University Marburg, Marburg 35043, Germany
| | - Harini Lakshminarasimhan
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Anna Stegmann
- Department of Neurology, Philipps University Marburg, Marburg 35043, Germany
| | - Benoit I Giasson
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Xiaobo Mao
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Valina L Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ted M Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Wolfgang H Oertel
- Department of Neurology, Philipps University Marburg, Marburg 35043, Germany
| | - D James Surmeier
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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Li J, Liu T, Dong Y, Kondoh K, Lu Z. Trans-synaptic Neural Circuit-Tracing with Neurotropic Viruses. Neurosci Bull 2019; 35:909-920. [PMID: 31004271 PMCID: PMC6754522 DOI: 10.1007/s12264-019-00374-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 12/15/2018] [Indexed: 12/19/2022] Open
Abstract
A central objective in deciphering the nervous system in health and disease is to define the connections of neurons. The propensity of neurotropic viruses to spread among synaptically-linked neurons makes them ideal for mapping neural circuits. So far, several classes of viral neuronal tracers have become available and provide a powerful toolbox for delineating neural networks. In this paper, we review the recent developments of neurotropic viral tracers and highlight their unique properties in revealing patterns of neuronal connections.
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Affiliation(s)
- Jiamin Li
- Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, The Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Taian Liu
- Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, The Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Yun Dong
- Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, The Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Kunio Kondoh
- Division of Endocrinology and Metabolism, Department of Homeostatic Regulation, National Institute for Physiological Sciences, National Institute of Natural Sciences, Myodaiji, Okazaki, Aichi, 444-8585, Japan.
- Japan Science and Technology Agency, PRESTO, Myodaiji, Okazaki, Aichi, 444-8585, Japan.
| | - Zhonghua Lu
- Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, The Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
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Abstract
Cortical networks are composed of glutamatergic excitatory projection neurons and local GABAergic inhibitory interneurons that gate signal flow and sculpt network dynamics. Although they represent a minority of the total neocortical neuronal population, GABAergic interneurons are highly heterogeneous, forming functional classes based on their morphological, electrophysiological, and molecular features, as well as connectivity and in vivo patterns of activity. Here we review our current understanding of neocortical interneuron diversity and the properties that distinguish cell types. We then discuss how the involvement of multiple cell types, each with a specific set of cellular properties, plays a crucial role in diversifying and increasing the computational power of a relatively small number of simple circuit motifs forming cortical networks. We illustrate how recent advances in the field have shed light onto the mechanisms by which GABAergic inhibition contributes to network operations.
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6
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Ghanem A, Conzelmann KK. G gene-deficient single-round rabies viruses for neuronal circuit analysis. Virus Res 2016; 216:41-54. [DOI: 10.1016/j.virusres.2015.05.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 05/28/2015] [Accepted: 05/31/2015] [Indexed: 12/11/2022]
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Osakada F. [From the connectome to brain function: rabies virus tools for elucidating structure and function of neural circuits]. Nihon Yakurigaku Zasshi 2015; 146:98-105. [PMID: 26256748 DOI: 10.1254/fpj.146.98] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Osakada F, Takahashi M. Challenges in retinal circuit regeneration: linking neuronal connectivity to circuit function. Biol Pharm Bull 2015; 38:341-57. [PMID: 25757915 DOI: 10.1248/bpb.b14-00771] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tremendous progress has been made in retinal regeneration, as exemplified by successful transplantation of retinal pigment epithelia and photoreceptor cells in the adult retina, as well as by generation of retinal tissue from embryonic stem cells and induced pluripotent cells. However, it remains unknown how new photoreceptors integrate within retinal circuits and contribute to vision restoration. There is a large gap in our understanding, at both the cellular and behavioral levels, of the functional roles of new neurons in the adult retina. This gap largely arises from the lack of appropriate methods for analyzing the organization and function of new neurons at the circuit level. To bridge this gap and understand the functional roles of new neurons in living animals, it will be necessary to identify newly formed connections, correlate them with function, manipulate their activity, and assess the behavioral outcome of these manipulations. Recombinant viral vectors are powerful tools not only for controlling gene expression and reprogramming cells, but also for tracing cell fates and neuronal connectivity, monitoring biological functions, and manipulating the physiological state of a specific cell population. These virus-based approaches, combined with electrophysiology and optical imaging, will provide circuit-level insight into neural regeneration and facilitate new strategies for achieving vision restoration in the adult retina. Herein, we discuss challenges and future directions in retinal regeneration research.
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Affiliation(s)
- Fumitaka Osakada
- Laboratory of Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya University; Systems Neurobiology Laboratory, The Salk Institute for Biological Studies, California 92037, USA; PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan.
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10
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Cauli B, Zhou X, Tricoire L, Toussay X, Staiger JF. Revisiting enigmatic cortical calretinin-expressing interneurons. Front Neuroanat 2014; 8:52. [PMID: 25009470 PMCID: PMC4067953 DOI: 10.3389/fnana.2014.00052] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/05/2014] [Indexed: 12/18/2022] Open
Abstract
Cortical calretinin (CR)-expressing interneurons represent a heterogeneous subpopulation of about 10-30% of GABAergic interneurons, which altogether total ca. 12-20% of all cortical neurons. In the rodent neocortex, CR cells display different somatodendritic morphologies ranging from bipolar to multipolar but the bipolar cells and their variations dominate. They are also diverse at the molecular level as they were shown to express numerous neuropeptides in different combinations including vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), neurokinin B (NKB) corticotrophin releasing factor (CRF), enkephalin (Enk) but also neuropeptide Y (NPY) and somatostatin (SOM) to a lesser extent. CR-expressing interneurons exhibit different firing behaviors such as adapting, bursting or irregular. They mainly originate from the caudal ganglionic eminence (CGE) but a subpopulation also derives from the dorsal part of the medial ganglionic eminence (MGE). Cortical GABAergic CR-expressing interneurons can be divided in two main populations: VIP-bipolar interneurons deriving from the CGE and SOM-Martinotti-like interneurons originating in the dorsal MGE. Although bipolar cells account for the majority of CR-expressing interneurons, the roles they play in cortical neuronal circuits and in the more general metabolic physiology of the brain remained elusive and enigmatic. The aim of this review is, firstly, to provide a comprehensive view of the morphological, molecular and electrophysiological features defining this cell type. We will, secondly, also summarize what is known about their place in the cortical circuit, their modulation by subcortical afferents and the functional roles they might play in neuronal processing and energy metabolism.
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Affiliation(s)
- Bruno Cauli
- Sorbonne Universités, UPMC University Paris 06, UM CR18, Neuroscience Paris Seine Paris, France ; Centre National de la Recherche Scientifique, UMR 8246, Neuroscience Paris Seine Paris, France ; Institut National de la Santé et de la Recherche Médicale, UMR-S 1130, Neuroscience Paris Seine Paris, France
| | - Xiaojuan Zhou
- Institute for Neuroanatomy, UMG, Georg-August-University Göttingen Göttingen, Germany
| | - Ludovic Tricoire
- Sorbonne Universités, UPMC University Paris 06, UM CR18, Neuroscience Paris Seine Paris, France ; Centre National de la Recherche Scientifique, UMR 8246, Neuroscience Paris Seine Paris, France ; Institut National de la Santé et de la Recherche Médicale, UMR-S 1130, Neuroscience Paris Seine Paris, France
| | - Xavier Toussay
- Sorbonne Universités, UPMC University Paris 06, UM CR18, Neuroscience Paris Seine Paris, France ; Centre National de la Recherche Scientifique, UMR 8246, Neuroscience Paris Seine Paris, France ; Institut National de la Santé et de la Recherche Médicale, UMR-S 1130, Neuroscience Paris Seine Paris, France
| | - Jochen F Staiger
- Institute for Neuroanatomy, UMG, Georg-August-University Göttingen Göttingen, Germany
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11
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Knotkova H, Nitsche MA, Cruciani RA. Putative physiological mechanisms underlying tDCS analgesic effects. Front Hum Neurosci 2013; 7:628. [PMID: 24133434 PMCID: PMC3783844 DOI: 10.3389/fnhum.2013.00628] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 09/10/2013] [Indexed: 11/21/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that induces changes in excitability, and activation of brain neurons and neuronal circuits. It has been observed that beyond regional effects under the electrodes, tDCS also alters activity of remote interconnected cortical and subcortical areas. This makes the tDCS stimulation technique potentially promising for modulation of pain syndromes. Indeed, utilizing specific montages, tDCS resulted in analgesic effects in experimental settings, as well as in post-operative acute pain and chronic pain syndromes. The promising evidence of tDCS-induced analgesic effects raises the challenging and complex question of potential physiologic mechanisms that underlie/mediate the accomplished pain relief. Here we present hypotheses on how the specific montages and targets for stimulation may affect the pain processing network.
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Affiliation(s)
- Helena Knotkova
- 1Department of Pain Medicine and Palliative Care, Institute for Non-Invasive Brain Stimulation, Research Division, Beth Israel Medical Center New York, NY, USA ; 2Department of Neurology, Albert Einstein College of Medicine Bronx, NY, USA
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Abstract
Rabies viruses, negative-strand RNA viruses, infect neurons through axon terminals and spread trans-synaptically in a retrograde direction between neurons. Rabies viruses whose glycoprotein (G) gene is deleted from the genome cannot spread across synapses. Complementation of G in trans, however, enables trans-synaptic spreading of G-deleted rabies viruses to directly connected, presynaptic neurons. Recombinant rabies viruses can encode genes of interest for labeling cells, controlling gene expression and monitoring or manipulating neural activity. Cre-dependent or bridge protein-mediated transduction and single-cell electroporation via the EnvA-TVA or EnvB-TVB (envelope glycoprotein and its specific receptor for avian sarcoma leukosis virus subgroup A or B) system allow cell type-specific or single cell-specific targeting. These rabies virus-based approaches permit the linking of connectivity to cell morphology and circuit function for particular cell types or single cells. Here we describe methods for construction of rabies viral vectors, recovery of G-deleted rabies viruses from cDNA, amplification of the viruses, pseudotyping them with EnvA or EnvB and concentration and titration of the viruses. The entire protocol takes 6-8 weeks.
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Ginger M, Haberl M, Conzelmann KK, Schwarz MK, Frick A. Revealing the secrets of neuronal circuits with recombinant rabies virus technology. Front Neural Circuits 2013; 7:2. [PMID: 23355811 PMCID: PMC3553424 DOI: 10.3389/fncir.2013.00002] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 01/05/2013] [Indexed: 01/06/2023] Open
Abstract
An understanding of how the brain processes information requires knowledge of the architecture of its underlying neuronal circuits, as well as insights into the relationship between architecture and physiological function. A range of sophisticated tools is needed to acquire this knowledge, and recombinant rabies virus (RABV) is becoming an increasingly important part of this essential toolbox. RABV has been recognized for years for its properties as a synapse-specific trans-neuronal tracer. A novel genetically modified variant now enables the investigation of specific monosynaptic connections. This technology, in combination with other genetic, physiological, optical, and computational tools, has enormous potential for the visualization of neuronal circuits, and for monitoring and manipulating their activity. Here we will summarize the latest developments in this fast moving field and provide a perspective for the use of this technology for the dissection of neuronal circuit structure and function in the normal and diseased brain.
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Affiliation(s)
- Melanie Ginger
- Neurocentre Magendie, INSERM U862 Bordeaux, France ; University of Bordeaux Bordeaux, France
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Clemo HR, Meredith MA. Dendritic spine density in multisensory versus primary sensory cortex. Synapse 2012; 66:714-24. [PMID: 22488884 DOI: 10.1002/syn.21560] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 03/22/2012] [Accepted: 03/23/2012] [Indexed: 11/09/2022]
Abstract
In sensory areas, neuronal dendritic spines receive sensory-specific inputs whose net activity drives neuronal spiking responses to effective external stimuli. Previous studies indicate that neurons in primary sensory cortical areas, which largely receive inputs from a single sensory modality, exhibit an average of 0.5-1.4 dendritic spines/μm, depending on species. In higher-order, associational cortices, inputs converge from multiple sensory sources onto individual, multisensory neurons. This raises the question: when inputs from two different modalities converge onto individual neurons, how are the dendritic spines apportioned to subserve the generation of robust spiking responses to each modality? As inputs arrive from two different sensory sources, it might be expected that neurons in multisensory areas exhibit approximately double the spine density of neurons in areas that receive just one sensory input. The present study examined this possibility in Golgi-stained neurons from ferret primary auditory (A1) and somatosensory (S1) cortices, as well as from regions in which inputs from two different sensory modalities converge: the lateral rostral suprasylvian sulcus (LRSS) and the rostral posterior parietal (PPr) areas. Dendritic spine density (spines/μm) was measured for pyramidal neurons in layers 2-3 and layers 5-6 for each cortical area from three animals using light microscopy. Primary sensory regions A1 and S1 showed remarkably similar average spine densities (A1 = 1.27 spines/μm ± 0.3 s.d.; S1 = 1.14 spines/μm ± 0.3), but average spine densities from the multisensory areas were lower (LRSS = 0.98 ± 0.3; PPr = 1.04 ± 0.3). Thus, for a given cortical area, dendritic spine density appears to be determined by factors other than the levels of sensory modality convergence.
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Affiliation(s)
- H Ruth Clemo
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, School of Medicine, Richmond, Virginia, USA.
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