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Shallow MC, Tian L, Lin H, Lefton KB, Chen S, Dougherty JD, Culver JP, Lambo ME, Hengen KB. At the onset of active whisking, the input layer of barrel cortex exhibits a 24 h window of increased excitability that depends on prior experience. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.04.597353. [PMID: 38895408 PMCID: PMC11185658 DOI: 10.1101/2024.06.04.597353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
The development of motor control over sensory organs is a critical milestone in sensory processing, enabling active exploration and shaping of the sensory environment. However, whether the onset of sensory organ motor control directly influences the development of corresponding sensory cortices remains unknown. Here, we exploit the late onset of whisking behavior in mice to address this question in the somatosensory system. Using ex vivo electrophysiology, we discovered a transient increase in the intrinsic excitability of excitatory neurons in layer IV of the barrel cortex, which processes whisker input, precisely coinciding with the onset of active whisking at postnatal day 14 (P14). This increase in neuronal gain was specific to layer IV, independent of changes in synaptic strength, and required prior sensory experience. Strikingly, the effect was not observed in layer II/III of the barrel cortex or in the visual cortex upon eye opening, suggesting a unique interaction between the development of active sensing and the thalamocortical input layer in the somatosensory system. Predictive modeling indicated that changes in active membrane conductances alone could reliably distinguish P14 neurons in control but not whisker-deprived hemispheres. Our findings demonstrate an experience-dependent, lamina-specific refinement of neuronal excitability tightly linked to the emergence of active whisking. This transient increase in the gain of the thalamic input layer coincides with a critical period for synaptic plasticity in downstream layers, suggesting a role in facilitating cortical maturation and sensory processing. Together, our results provide evidence for a direct interaction between the development of motor control and sensory cortex, offering new insights into the experience-dependent development and refinement of sensory systems. These findings have broad implications for understanding the interplay between motor and sensory development, and how the mechanisms of perception cooperate with behavior.
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Affiliation(s)
| | - Lucy Tian
- Department of Biology, Washington University in Saint Louis
| | - Hudson Lin
- Department of Biology, Washington University in Saint Louis
| | - Katheryn B Lefton
- Department of Biology, Washington University in Saint Louis
- Department of Neuroscience, Washington University in Saint Louis
| | - Siyu Chen
- Department of Genetics, Washington University in Saint Louis
| | | | - Joe P Culver
- Department of Radiology, Washington University in Saint Louis
| | - Mary E Lambo
- Department of Biology, Washington University in Saint Louis
| | - Keith B Hengen
- Department of Biology, Washington University in Saint Louis
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2
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Richardson AM, Sokoloff G, Blumberg MS. Developmentally unique cerebellar processing prioritizes self-over other-generated movements. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.16.571990. [PMID: 38168365 PMCID: PMC10760083 DOI: 10.1101/2023.12.16.571990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Animals must distinguish the sensory consequences of self-generated movements (reafference) from those of other-generated movements (exafference). Only self-generated movements entail the production of motor copies (i.e., corollary discharges), which are compared with reafference in the cerebellum to compute predictive or internal models of movement. Internal models emerge gradually over the first three postnatal weeks in rats through a process that is not yet fully understood. Previously, we demonstrated in postnatal day (P) P8 and P12 rats that precerebellar nuclei convey corollary discharge and reafference to the cerebellum during active (REM) sleep when pups produce limb twitches. Here, recording from a deep cerebellar nucleus (interpositus, IP) in P12 rats of both sexes, we compared reafferent and exafferent responses to twitches and limb stimulations, respectively. As expected, most IP units showed robust responses to twitches. However, in contrast with other sensory structures throughout the brain, relatively few IP units showed exafferent responses. Upon finding that exafferent responses occurred in pups under urethane anesthesia, we hypothesized that urethane inhibits cerebellar cortical cells, thereby disinhibiting exafferent responses in IP. In support of this hypothesis, ablating cortical tissue dorsal to IP mimicked the effects of urethane on exafference. Finally, the results suggest that twitch-related corollary discharge and reafference are conveyed simultaneously and in parallel to cerebellar cortex and IP. Based on these results, we propose that twitches provide opportunities for the nascent cerebellum to integrate somatotopically organized corollary discharge and reafference, thereby enabling the development of closed-loop circuits and, subsequently, internal models.
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Affiliation(s)
- Angela M. Richardson
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, U.S.A
| | - Greta Sokoloff
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, 52242, U.S.A
- Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, 52242, U.S.A
| | - Mark S. Blumberg
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA 52242, U.S.A
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, 52242, U.S.A
- Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, 52242, U.S.A
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3
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Plutino S, Laghouati E, Jarre G, Depaulis A, Guillemain I, Bureau I. Barrel cortex development lacks a key stage of hyperconnectivity from deep to superficial layers in a rat model of Absence Epilepsy. Prog Neurobiol 2024; 234:102564. [PMID: 38244975 DOI: 10.1016/j.pneurobio.2023.102564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 12/04/2023] [Accepted: 12/30/2023] [Indexed: 01/22/2024]
Abstract
During development of the sensory cortex, the ascending innervation from deep to upper layers provides a temporary scaffold for the construction of other circuits that remain at adulthood. Whether an alteration in this sequence leads to brain dysfunction in neuro-developmental diseases remains unknown. Using functional approaches in a genetic model of Absence Epilepsy (GAERS), we investigated in barrel cortex, the site of seizure initiation, the maturation of excitatory and inhibitory innervations onto layer 2/3 pyramidal neurons and cell organization into neuronal assemblies. We found that cortical development in GAERS lacks the early surge of connections originating from deep layers observed at the end of the second postnatal week in normal rats and the concomitant structuring into multiple assemblies. Later on, at seizure onset (1 month old), excitatory neurons are hyper-excitable in GAERS when compared to Wistar rats. These findings suggest that early defects in the development of connectivity could promote this typical epileptic feature and/or its comorbidities.
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Affiliation(s)
| | - Emel Laghouati
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Guillaume Jarre
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Antoine Depaulis
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Isabelle Guillemain
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
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4
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Wang M, Yu X. Experience-dependent structural plasticity of pyramidal neurons in the developing sensory cortices. Curr Opin Neurobiol 2023; 81:102724. [PMID: 37068383 DOI: 10.1016/j.conb.2023.102724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 03/16/2023] [Accepted: 03/17/2023] [Indexed: 04/19/2023]
Abstract
Sensory experience regulates the structural and functional wiring of neuronal circuits, during development and throughout adulthood. Here, we review current knowledge of how experience affects structural plasticity of pyramidal neurons in the sensory cortices. We discuss the pros and cons of existing labeling approaches, as well as what structural parameters are most plastic. We further discuss how recent advances in sparse labeling of specific neuronal subtypes, as well as development of techniques that allow fast, high resolution imaging in large fields, would enable future studies to address currently unanswered questions in the field of structural plasticity.
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Affiliation(s)
- Miao Wang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, and PKU-IDG/McGovern Institute, Peking University, Beijing 100871, China.
| | - Xiang Yu
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, and PKU-IDG/McGovern Institute, Peking University, Beijing 100871, China; Autism Research Center of Peking University Health Science Center, Beijing 100191, China; Chinese Institute for Brain Research, Beijing 102206, China.
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5
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Itami C, Uesaka N, Huang JY, Lu HC, Sakimura K, Kano M, Kimura F. Endocannabinoid-dependent formation of columnar axonal projection in the mouse cerebral cortex. Proc Natl Acad Sci U S A 2022; 119:e2122700119. [PMID: 36067295 PMCID: PMC9477236 DOI: 10.1073/pnas.2122700119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 07/19/2022] [Indexed: 11/18/2022] Open
Abstract
Columnar structure is one of the most fundamental morphological features of the cerebral cortex and is thought to be the basis of information processing in higher animals. Yet, how such a topographically precise structure is formed is largely unknown. Formation of columnar projection of layer 4 (L4) axons is preceded by thalamocortical formation, in which type 1 cannabinoid receptors (CB1R) play an important role in shaping barrel-specific targeted projection by operating spike timing-dependent plasticity during development (Itami et al., J. Neurosci. 36, 7039-7054 [2016]; Kimura & Itami, J. Neurosci. 39, 3784-3791 [2019]). Right after the formation of thalamocortical projections, CB1Rs start to function at L4 axon terminals (Itami & Kimura, J. Neurosci. 32, 15000-15011 [2012]), which coincides with the timing of columnar shaping of L4 axons. Here, we show that the endocannabinoid 2-arachidonoylglycerol (2-AG) plays a crucial role in columnar shaping. We found that L4 axon projections were less organized until P12 and then became columnar after CB1Rs became functional. By contrast, the columnar organization of L4 axons was collapsed in mice genetically lacking diacylglycerol lipase α, the major enzyme for 2-AG synthesis. Intraperitoneally administered CB1R agonists shortened axon length, whereas knockout of CB1R in L4 neurons impaired columnar projection of their axons. Our results suggest that endocannabinoid signaling is crucial for shaping columnar axonal projection in the cerebral cortex.
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Affiliation(s)
- Chiaki Itami
- Department of Physiology, Faculty of Medicine, Saitama Medical University, Moroyama, Saitama 350-0495, Japan
- The Linda and Jack Gill Center for Biomolecular Sciences, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405
| | - Naofumi Uesaka
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033, Japan
- Present address, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Jui-Yen Huang
- The Linda and Jack Gill Center for Biomolecular Sciences, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405
| | - Hui-Chen Lu
- The Linda and Jack Gill Center for Biomolecular Sciences, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, 951-8585, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033, Japan
- International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo, 113-0033, Japan
| | - Fumitaka Kimura
- Department of Molecular Neuroscience, Osaka University Graduate School of Medicine, Suita 565-0871, Japan
- Laboratory of Brain Neuroscience, Faculty of Medical Sciences, Jikei University of Health Care and Sciences, Osaka, 532-0003, Japan
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6
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Nakazawa S, Iwasato T. Spatial organization and transitions of spontaneous neuronal activities in the developing sensory cortex. Dev Growth Differ 2021; 63:323-339. [PMID: 34166527 DOI: 10.1111/dgd.12739] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 12/30/2022]
Abstract
The sensory cortex underlies our ability to perceive and interact with the external world. Sensory perceptions are controlled by specialized neuronal circuits established through fine-tuning, which relies largely on neuronal activity during the development. Spontaneous neuronal activity is an essential driving force of neuronal circuit refinement. At early developmental stages, sensory cortices display spontaneous activities originating from the periphery and characterized by correlated firing arranged spatially according to the modality. The firing patterns are reorganized over time and become sparse, which is typical for the mature brain. This review focuses mainly on rodent sensory cortices. First, the features of the spontaneous activities during early postnatal stages are described. Then, the developmental changes in the spatial organization of the spontaneous activities and the transition mechanisms involved are discussed. The identification of the principles controlling the spatial organization of spontaneous activities in the developing sensory cortex is essential to understand the self-organization process of neuronal circuits.
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Affiliation(s)
- Shingo Nakazawa
- Laboratory of Mammalian Neural Circuits, National Institute of Genetics, Mishima, Japan.,Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Takuji Iwasato
- Laboratory of Mammalian Neural Circuits, National Institute of Genetics, Mishima, Japan.,Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan
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7
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Tenkumo C, Ohta KI, Suzuki S, Warita K, Irie K, Teradaya S, Kusaka T, Kanenishi K, Hata T, Miki T. Repeated maternal separation causes transient reduction in BDNF expression in the medial prefrontal cortex during early brain development, affecting inhibitory neuron development. Heliyon 2020; 6:e04781. [PMID: 32923721 PMCID: PMC7475105 DOI: 10.1016/j.heliyon.2020.e04781] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/08/2020] [Accepted: 08/14/2020] [Indexed: 01/25/2023] Open
Abstract
It is widely accepted that maternal separation (MS) induces stress in children and disrupts neural circuit formation during early brain development. Even though such disruption occurs transiently early in life, its influence persists after maturation, and could lead to various neurodevelopmental disorders. Our recent study revealed that repeated MS reduces the number of inhibitory neurons and synapses in the medial prefrontal cortex (mPFC) and causes mPFC-related social deficits after maturation. However, how MS impedes mPFC development during early brain development remains poorly understood. Here, we focused on brain-derived neurotrophic factor (BDNF) involved in the development of inhibitory neurons, and examined time-dependent BDNF expression in the mPFC during the pre-weaning period in male rats exposed to MS. Our results show that MS attenuates BDNF expression only around the end of the first postnatal week. Likewise, mRNA expression of activity-regulated cytoskeleton-associated protein (Arc), an immediate-early gene whose expression is partly regulated by BDNF, also decreased in the MS group along with the reduction in BDNF expression. On the contrary, mRNA expression of tropomyosin-related kinase B (TrkB), which is a BDNF receptor, was scarcely altered, while its protein expression decreased in the MS group only during the weaning period. In addition, MS reduced mRNA levels of glutamic acid decarboxylase (GAD) 65, a GABA synthesizing enzyme, only during the weaning period. Our results suggest that repeated MS temporarily attenuates BDNF signaling in the mPFC during early brain development. BDNF plays a crucial role in the development of inhibitory neurons; therefore, transient attenuation of BDNF signaling may cause delays in GABAergic neuron development in the mPFC.
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Affiliation(s)
- Chiaki Tenkumo
- Department of Perinatology and Gynecology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Ken-ichi Ohta
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
- Corresponding author.
| | - Shingo Suzuki
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Katsuhiko Warita
- Department of Veterinary Anatomy, Faculty of Agriculture, Tottori University, Tottori, Japan
| | - Kanako Irie
- Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Saki Teradaya
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Takashi Kusaka
- Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Kenji Kanenishi
- Department of Perinatology and Gynecology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Toshiyuki Hata
- Department of Perinatology and Gynecology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Takanori Miki
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
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8
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LeMessurier AM, Laboy-Juárez KJ, McClain K, Chen S, Nguyen T, Feldman DE. Enrichment drives emergence of functional columns and improves sensory coding in the whisker map in L2/3 of mouse S1. eLife 2019; 8:46321. [PMID: 31418693 PMCID: PMC6697414 DOI: 10.7554/elife.46321] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 08/01/2019] [Indexed: 12/02/2022] Open
Abstract
Sensory maps in layer (L) 2/3 of rodent cortex lack precise functional column boundaries, and instead exhibit locally heterogeneous (salt-and-pepper) tuning superimposed on smooth global topography. Could this organization be a byproduct of impoverished experience in laboratory housing? We compared whisker map somatotopy in L2/3 and L4 excitatory cells of somatosensory (S1) cortex in normally housed vs. tactile-enriched mice, using GCaMP6s imaging. Normally housed mice had a dispersed, salt-and-pepper whisker map in L2/3, but L4 was more topographically precise. Enrichment (P21 to P46-71) sharpened whisker tuning and decreased, but did not abolish, local tuning heterogeneity. In L2/3, enrichment strengthened and sharpened whisker point representations, and created functional boundaries of tuning similarity and noise correlations at column edges. Thus, enrichment drives emergence of functional columnar topography in S1, and reduces local tuning heterogeneity. These changes predict better touch detection by neural populations within each column.
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Affiliation(s)
- Amy M LeMessurier
- Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
| | - Keven J Laboy-Juárez
- Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
| | - Kathryn McClain
- Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
| | - Shilin Chen
- Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
| | - Theresa Nguyen
- Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
| | - Daniel E Feldman
- Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
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9
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Kast RJ, Levitt P. Precision in the development of neocortical architecture: From progenitors to cortical networks. Prog Neurobiol 2019; 175:77-95. [PMID: 30677429 PMCID: PMC6402587 DOI: 10.1016/j.pneurobio.2019.01.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 01/02/2019] [Accepted: 01/21/2019] [Indexed: 02/07/2023]
Abstract
Of all brain regions, the 6-layered neocortex has undergone the most dramatic changes in size and complexity during mammalian brain evolution. These changes, occurring in the context of a conserved set of organizational features that emerge through stereotypical developmental processes, are considered responsible for the cognitive capacities and sensory specializations represented within the mammalian clade. The modern experimental era of developmental neurobiology, spanning 6 decades, has deciphered a number of mechanisms responsible for producing the diversity of cortical neuron types, their precise connectivity and the role of gene by environment interactions. Here, experiments providing insight into the development of cortical projection neuron differentiation and connectivity are reviewed. This current perspective integrates discussion of classic studies and new findings, based on recent technical advances, to highlight an improved understanding of the neuronal complexity and precise connectivity of cortical circuitry. These descriptive advances bring new opportunities for studies related to the developmental origins of cortical circuits that will, in turn, improve the prospects of identifying pathogenic targets of neurodevelopmental disorders.
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Affiliation(s)
- Ryan J Kast
- Department of Pediatrics and Program in Developmental Neuroscience and Developmental Neurogenetics, The Saban Research Institute, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90027, USA
| | - Pat Levitt
- Department of Pediatrics and Program in Developmental Neuroscience and Developmental Neurogenetics, The Saban Research Institute, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90027, USA.
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10
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The pial vasculature of the mouse develops according to a sensory-independent program. Sci Rep 2018; 8:9860. [PMID: 29959346 PMCID: PMC6026131 DOI: 10.1038/s41598-018-27910-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
The cerebral vasculature is organized to supply the brain’s metabolic needs. Sensory deprivation during the early postnatal period causes altered neural activity and lower metabolic demand. Neural activity is instructional for some aspects of vascular development, and deprivation causes changes in capillary density in the deprived brain region. However, it is not known if the pial arteriole network, which contains many leptomeningeal anastomoses (LMAs) that endow the network with redundancy against occlusions, is also affected by sensory deprivation. We quantified the effects of early-life sensory deprivation via whisker plucking on the densities of LMAs and penetrating arterioles (PAs) in anatomically-identified primary sensory regions (vibrissae cortex, forelimb/hindlimb cortex, visual cortex and auditory cortex) in mice. We found that the densities of penetrating arterioles were the same across cortical regions, though the hindlimb representation had a higher density of LMAs than other sensory regions. We found that the densities of PAs and LMAs, as well as quantitative measures of network topology, were not affected by sensory deprivation. Our results show that the postnatal development of the pial arterial network is robust to sensory deprivation.
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11
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Yang JW, Kilb W, Kirischuk S, Unichenko P, Stüttgen MC, Luhmann HJ. Development of the whisker-to-barrel cortex system. Curr Opin Neurobiol 2018; 53:29-34. [PMID: 29738998 DOI: 10.1016/j.conb.2018.04.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/20/2018] [Accepted: 04/24/2018] [Indexed: 01/30/2023]
Abstract
This review provides an overview on the development of the rodent whisker-to-barrel cortex system from late embryonic stage to the end of the first postnatal month. During this period the system shows a remarkable transition from a mostly genetic-molecular driven generation of crude connectivity, providing the template for activity-dependent structural and functional maturation and plasticity, to the manifestation of a complex behavioral repertoire including social interactions. Spontaneous and sensory-evoked activity is present in neonatal barrel cortex and control the generation of the cortical architecture. Half a century after its first description by Woolsey and van der Loos the whisker-to-barrel cortex system with its unique and clear topographic organization still offers the exceptional opportunity to study sensory processing and complex behavior.
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Affiliation(s)
- Jenq-Wei Yang
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Werner Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Sergei Kirischuk
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Petr Unichenko
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Maik C Stüttgen
- Institute of Pathophysiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany
| | - Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany.
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12
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Abstract
Somatosensory areas containing topographic maps of the body surface are a major feature of parietal cortex. In primates, parietal cortex contains four somatosensory areas, each with its own map, with the primary cutaneous map in area 3b. Rodents have at least three parietal somatosensory areas. Maps are not isomorphic to the body surface, but magnify behaviorally important skin regions, which include the hands and face in primates, and the whiskers in rodents. Within each map, intracortical circuits process tactile information, mediate spatial integration, and support active sensation. Maps may also contain fine-scale representations of touch submodalities, or direction of tactile motion. Functional representations are more overlapping than suggested by textbook depictions of map topography. The whisker map in rodent somatosensory cortex is a canonic system for studying cortical microcircuits, sensory coding, and map plasticity. Somatosensory maps are plastic throughout life in response to altered use or injury. This chapter reviews basic principles and recent findings in primate, human, and rodent somatosensory maps.
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Affiliation(s)
- Samuel Harding-Forrester
- Department of Molecular and Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States
| | - Daniel E Feldman
- Department of Molecular and Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States.
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13
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Lo SQ, Sng JCG, Augustine GJ. Defining a critical period for inhibitory circuits within the somatosensory cortex. Sci Rep 2017; 7:7271. [PMID: 28779074 PMCID: PMC5544762 DOI: 10.1038/s41598-017-07400-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 06/28/2017] [Indexed: 11/21/2022] Open
Abstract
Although experience-dependent changes in brain inhibitory circuits are thought to play a key role during the “critical period” of brain development, the nature and timing of these changes are poorly understood. We examined the role of sensory experience in sculpting an inhibitory circuit in the primary somatosensory cortex (S1) of mice by using optogenetics to map the connections between parvalbumin (PV) expressing interneurons and layer 2/3 pyramidal cells. Unilateral whisker deprivation decreased the strength and spatial range of inhibitory input provided to pyramidal neurons by PV interneurons in layers 2/3, 4 and 5. By varying the time when sensory input was removed, we determined that the critical period closes around postnatal day 14. This yields the first precise time course of critical period plasticity for an inhibitory circuit.
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Affiliation(s)
- Shun Qiang Lo
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,Institute of Molecular and Cell Biology (A*STAR), Singapore, Singapore.,Marine Biological Laboratory, Woods Hole, USA
| | - Judy C G Sng
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Singapore Institute of Clinical Sciences, Agency for Science and Technology (A*STAR), Singapore, Singapore
| | - George J Augustine
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. .,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore. .,Institute of Molecular and Cell Biology (A*STAR), Singapore, Singapore. .,Marine Biological Laboratory, Woods Hole, USA.
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14
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Pluta SR, Lyall EH, Telian GI, Ryapolova-Webb E, Adesnik H. Surround Integration Organizes a Spatial Map during Active Sensation. Neuron 2017; 94:1220-1233.e5. [PMID: 28504117 DOI: 10.1016/j.neuron.2017.04.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 03/05/2017] [Accepted: 04/18/2017] [Indexed: 01/09/2023]
Abstract
During active sensation, sensors scan space in order to generate a representation of the outside world. However, since spatial coding in sensory systems is typically addressed by measuring receptive fields in a fixed, sensor-based coordinate frame, the cortical representation of scanned space is poorly understood. To address this question, we probed spatial coding in the rodent whisker system using a combination of two-photon imaging and electrophysiology during active touch. We found that surround whiskers powerfully transform the cortical representation of scanned space. On the single-neuron level, surround input profoundly alters response amplitude and modulates spatial preference in the cortex. On the population level, surround input organizes the spatial preference of neurons into a continuous map of the space swept out by the whiskers. These data demonstrate how spatial summation over a moving sensor array is critical to generating population codes of sensory space.
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Affiliation(s)
- Scott R Pluta
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Evan H Lyall
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Greg I Telian
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Elena Ryapolova-Webb
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Hillel Adesnik
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
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15
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Itami C, Kimura F. Concurrently induced plasticity due to convergence of distinct forms of spike timing-dependent plasticity in the developing barrel cortex. Eur J Neurosci 2016; 44:2984-2990. [PMID: 27726220 DOI: 10.1111/ejn.13431] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/04/2016] [Accepted: 10/06/2016] [Indexed: 01/17/2023]
Abstract
Spike timing-dependent plasticity (STDP) has been demonstrated in a variety of neural circuits. Recent studies reveal that it plays a fundamental role in the formation and remodeling of neuronal circuits. We show here an interaction of two distinct forms of STDP in the mouse barrel cortex causing concurrent, plastic changes, potentially a novel mechanism underlying network remodeling. We previously demonstrated that during the second postnatal week, when layer four (L4) cells are forming synapses onto L2/3 cells, L4-L2/3 synapses exhibit STDP with only long-term potentiation (t-LTP). We also showed that at the same developmental stage, thalamus-L2/3 synapses express functional cannabinoid type 1 receptor (CB1R) and exhibit CB1R-dependent STDP with only long-term depression (t-LTD). Thus, distinct forms of STDP with opposite directions (potentiation vs. depression) converge in the target layer of L2/3 during the second postnatal week. As the canonical target layer of the thalamus is L4 and thalamic cells activate both L4 and L2/3 cells, in principle, thalamic activity could induce t-LTP at L4-L2/3 and t-LTD at thalamus-L2/3 simultaneously. In this study, we tested this possibility. We found that when spike timing stimulation was applied to the thalamus and L2/3 cells, synapses between the thalamus and L2/3 were weakened, whereas synapses between L4 and L2/3 were potentiated; therefore, converging STDP caused the predicted concurrent plasticity. We propose that developmentally transient convergences of STDP may play a role in shaping neural networks by facilitating L4-L2/3 formation and weakening aberrant thalamic innervation to L2/3, both driven by thalamic activity.
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Affiliation(s)
- Chiaki Itami
- Department of Physiology, Faculty of Medicine, Saitama Medical University, Moroyama, Saitama, 350-0495, Japan
| | - Fumitaka Kimura
- Department of Molecular Neuroscience, Osaka University Graduate School of Medicine, Suita, 565-0871, Japan
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16
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Valiullina F, Akhmetshina D, Nasretdinov A, Mukhtarov M, Valeeva G, Khazipov R, Rozov A. Developmental Changes in Electrophysiological Properties and a Transition from Electrical to Chemical Coupling between Excitatory Layer 4 Neurons in the Rat Barrel Cortex. Front Neural Circuits 2016; 10:1. [PMID: 26834567 PMCID: PMC4720737 DOI: 10.3389/fncir.2016.00001] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/02/2016] [Indexed: 11/22/2022] Open
Abstract
During development, sensory systems switch from an immature to an adult mode of function along with the emergence of the active cortical states. Here, we used patch-clamp recordings from neocortical slices in vitro to characterize the developmental changes in the basic electrophysiological properties of excitatory L4 neurons and their connectivity before and after the developmental switch, which occurs in the rat barrel cortex in vivo at postnatal day P8. Prior to the switch, L4 neurons had higher resting membrane potentials, higher input resistance, lower membrane capacity, as well as action potentials (APs) with smaller amplitudes, longer durations and higher AP thresholds compared to the neurons after the switch. A sustained firing pattern also emerged around the switch. Dual patch-clamp recordings from L4 neurons revealed that recurrent connections between L4 excitatory cells do not exist before and develop rapidly across the switch. In contrast, electrical coupling between these neurons waned around the switch. We suggest that maturation of electrophysiological features, particularly acquisition of a sustained firing pattern, and a transition from the immature electrical to mature chemical synaptic coupling between excitatory L4 neurons, contributes to the developmental switch in the cortical mode of function.
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Affiliation(s)
- Fliza Valiullina
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal University Kazan, Russia
| | - Dinara Akhmetshina
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal University Kazan, Russia
| | - Azat Nasretdinov
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal University Kazan, Russia
| | - Marat Mukhtarov
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal University Kazan, Russia
| | - Guzel Valeeva
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal University Kazan, Russia
| | - Roustem Khazipov
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal UniversityKazan, Russia; Institut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale UMR901Marseille, France; Aix-Marseille UniversityMarseille, France
| | - Andrei Rozov
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal UniversityKazan, Russia; Department of Physiology and Pathophysiology, University of HeidelbergHeidelberg, Germany
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17
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Martens MB, Celikel T, Tiesinga PHE. A Developmental Switch for Hebbian Plasticity. PLoS Comput Biol 2015; 11:e1004386. [PMID: 26172394 PMCID: PMC4501799 DOI: 10.1371/journal.pcbi.1004386] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 06/08/2015] [Indexed: 12/12/2022] Open
Abstract
Hebbian forms of synaptic plasticity are required for the orderly development of sensory circuits in the brain and are powerful modulators of learning and memory in adulthood. During development, emergence of Hebbian plasticity leads to formation of functional circuits. By modeling the dynamics of neurotransmitter release during early postnatal cortical development we show that a developmentally regulated switch in vesicle exocytosis mode triggers associative (i.e. Hebbian) plasticity. Early in development spontaneous vesicle exocytosis (SVE), often considered as 'synaptic noise', is important for homogenization of synaptic weights and maintenance of synaptic weights in the appropriate dynamic range. Our results demonstrate that SVE has a permissive, whereas subsequent evoked vesicle exocytosis (EVE) has an instructive role in the expression of Hebbian plasticity. A timed onset for Hebbian plasticity can be achieved by switching from SVE to EVE and the balance between SVE and EVE can control the effective rate of Hebbian plasticity. We further show that this developmental switch in neurotransmitter release mode enables maturation of spike-timing dependent plasticity. A mis-timed or inadequate SVE to EVE switch may lead to malformation of brain networks thereby contributing to the etiology of neurodevelopmental disorders. Neurotransmitter release is the principal form of chemical communication in the brain. When an action potential reaches a synapse, calcium influx activates the machinery for neurotransmitter release. During early neuronal development this machinery matures such that neurotransmitter release becomes time-locked to action potentials. By modeling this change in neurotransmitter release, we mechanistically show that the maturation process can be solely responsible for switching on associative (i.e. Hebbian) plasticity in the brain. The relevant proteins of the release machinery can thereby regulate the rate at which neural circuits represent sensory input, providing a novel mechanism to control the learning rate and onset. Appropriately timing of the onset of Hebbian plasticity is important because during early development sensory experience fine-tunes, often irreversibly, the neural wiring in our brain.
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Affiliation(s)
- Marijn B. Martens
- Donders Institute for Brain, Cognition and Behaviour, Centre for Neuroscience, Department of Neuroinformatics, Radboud University Nijmegen, Nijmegen, The Netherlands
- * E-mail:
| | - Tansu Celikel
- Donders Institute for Brain, Cognition and Behaviour, Centre for Neuroscience, Department of Neurophysiology, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Paul H. E. Tiesinga
- Donders Institute for Brain, Cognition and Behaviour, Centre for Neuroscience, Department of Neuroinformatics, Radboud University Nijmegen, Nijmegen, The Netherlands
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18
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Erlandson MA, Manzoni OJ, Bureau I. The Functional Organization of Neocortical Networks Investigated in Slices with Local Field Recordings and Laser Scanning Photostimulation. PLoS One 2015; 10:e0132008. [PMID: 26134668 PMCID: PMC4489676 DOI: 10.1371/journal.pone.0132008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 06/09/2015] [Indexed: 02/07/2023] Open
Abstract
The organization of cortical networks can be investigated functionally in brain slices. Laser scanning photostimulation (LSPS) with glutamate-uncaging allows for a rapid survey of all connections impinging on single cells recorded in patch-clamp. We sought to develop a variant of the method that would allow for a more exhaustive mapping of neuronal networks at every experiment. We found that the extracellular field recordings could be used to detect synaptic responses evoked by LSPS. One to two electrodes were placed in all six cortical layers of barrel cortex successively and maps were computed from the size of synaptic negative local field potentials. The field maps displayed a laminar organization similar to the one observed in maps computed from excitatory postsynaptic currents recorded in patch-clamp mode. Thus, LSPS combined with field recording is an interesting alternative to obtain for every animal tested a comprehensive map of the excitatory intracortical network.
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Affiliation(s)
- Melissa A. Erlandson
- U901 INMED, INSERM, Marseille, France
- UMRS 901, Aix-Marseille University, Marseille, France
| | - Olivier J. Manzoni
- U901 INMED, INSERM, Marseille, France
- UMRS 901, Aix-Marseille University, Marseille, France
| | - Ingrid Bureau
- U901 INMED, INSERM, Marseille, France
- UMRS 901, Aix-Marseille University, Marseille, France
- * E-mail:
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19
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Meredith R. Sensitive and critical periods during neurotypical and aberrant neurodevelopment: A framework for neurodevelopmental disorders. Neurosci Biobehav Rev 2015; 50:180-8. [DOI: 10.1016/j.neubiorev.2014.12.001] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 10/21/2014] [Accepted: 12/01/2014] [Indexed: 01/16/2023]
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20
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Yamawaki N, Borges K, Suter BA, Harris KD, Shepherd GMG. A genuine layer 4 in motor cortex with prototypical synaptic circuit connectivity. eLife 2014; 3:e05422. [PMID: 25525751 PMCID: PMC4290446 DOI: 10.7554/elife.05422] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 12/18/2014] [Indexed: 12/28/2022] Open
Abstract
The motor cortex (M1) is classically considered an agranular area, lacking a distinct layer 4 (L4). Here, we tested the idea that M1, despite lacking a cytoarchitecturally visible L4, nevertheless possesses its equivalent in the form of excitatory neurons with input–output circuits like those of the L4 neurons in sensory areas. Consistent with this idea, we found that neurons located in a thin laminar zone at the L3/5A border in the forelimb area of mouse M1 have multiple L4-like synaptic connections: excitatory input from thalamus, largely unidirectional excitatory outputs to L2/3 pyramidal neurons, and relatively weak long-range corticocortical inputs and outputs. M1-L4 neurons were electrophysiologically diverse but morphologically uniform, with pyramidal-type dendritic arbors and locally ramifying axons, including branches extending into L2/3. Our findings therefore identify pyramidal neurons in M1 with the expected prototypical circuit properties of excitatory L4 neurons, and question the traditional assumption that motor cortex lacks this layer. DOI:http://dx.doi.org/10.7554/eLife.05422.001 In 1909, a German scientist called Korbinian Brodmann published the first map of the outer layer of the human brain. After staining neurons with a dye and studying the structures of the cells and how they were organized, he realized that he could divide the cortex into 43 numbered regions. Most Brodmann areas can be divided into a number of horizontal layers, with layer 1 being closest to the surface of the brain. Neurons in the different layers form distinct sets of connections, and the relative thickness of the layers has implications for the function carried out by that area. It is thought, for example, that the motor cortex does not have a layer 4, which suggests that the neural circuitry that controls movement differs from that in charge of vision, hearing, and other functions. Yamawaki et al. now challenge this view by providing multiple lines of evidence for the existence of layer 4 in the motor cortex in mice. Neurons at the border between layer 3 and layer 5A in the motor cortex possess many of the same properties as the neurons in layer 4 in sensory cortex. In particular, they receive inputs from a brain region called the thalamus, and send outputs to neurons in layers 2 and 3. Yamawaki et al. go on to characterize some of the properties of the neurons in the putative layer 4 of the motor cortex, finding that they do not look like the specialized ‘stellate’ cells that are found in some other areas of the cortex. Instead, they resemble the ‘pyramidal’ type of neuron that is found in all layers and areas of the cortex. The discovery that the motor cortex is more similar in its circuit connections to other area of the cortex than previously thought has important implications for our understanding of this region of the brain. DOI:http://dx.doi.org/10.7554/eLife.05422.002
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Affiliation(s)
- Naoki Yamawaki
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Katharine Borges
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Benjamin A Suter
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Kenneth D Harris
- Institute of Neurology, University College London, London, United Kingdom
| | - Gordon M G Shepherd
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
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21
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Vitali I, Jabaudon D. Synaptic biology of barrel cortex circuit assembly. Semin Cell Dev Biol 2014; 35:156-64. [PMID: 25080022 DOI: 10.1016/j.semcdb.2014.07.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 07/10/2014] [Accepted: 07/17/2014] [Indexed: 02/04/2023]
Abstract
Mature neuronal circuits arise from the coordinated interplay of cell-intrinsic differentiation programs, target-derived signals and activity-dependent processes. Typically, cell-intrinsic mechanisms predominate at early stages of differentiation, while input-dependent processes modulate circuit formation at later stages of development. The whisker barrel cortex of rodents is particularly well suited to study this latter phase. During the first few days after birth, thalamocortical axons (TCA) from the somatosensory ventral posteromedial nucleus (VPM) form synapses onto layer 4 (L4) neurons, which aggregate to form barrels, whose spatial organization corresponds to the distribution of the whiskers on the snout. Besides specific genetic programs, which control TCA and L4 neuron specification, the establishment of the barrel pattern also depends on the information resulting from whisker activation. The plasticity of this system during the first few days after birth is critical for barrel formation: damage to the sensory periphery impairs TCA patterning, while lesions after this period have less pronounced effects. Here, we will review the role and position of L4 neurons within cortical columnar circuits and synaptogenesis during barrel formation.
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Affiliation(s)
- Ilaria Vitali
- Department of Basic Neurosciences, University of Geneva, Switzerland
| | - Denis Jabaudon
- Department of Basic Neurosciences, University of Geneva, Switzerland.
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22
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Ghoshal A, Lustig B, Popescu M, Ebner F, Pouget P. Unilateral whisker trimming in newborn rats alters neuronal coincident discharge among mature barrel cortex neurons. J Neurophysiol 2014; 112:1925-35. [PMID: 25057142 DOI: 10.1152/jn.00562.2013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is known that sensory deprivation, including postnatal whisker trimming, can lead to severe deficits in the firing rate properties of cortical neurons. Recent results indicate that development of synchronous discharge among cortical neurons is also activity influenced, and that correlated discharge is significantly impaired following loss of bilateral sensory input in rats. Here we investigate whether unilateral whisker trimming (unilateral deprivation or UD) after birth interferes in the same way with the development of synchronous discharge in cortex. We measured the coincidence of spikes among pairs of neurons recorded under urethane anesthesia in one whisker barrel field deprived by trimming all contralateral whiskers for 60 days after birth (UD), and in untrimmed controls (CON). In the septal columns around barrels, UD significantly increased the coincident discharge among cortical neurons compared with CON, most notably in layers II/III. In contrast, synchronous discharge was normal between layer IV UD barrel neurons: i.e., not different from CON. Thus, while bilateral whisker deprivation (BD) produced a global deficit in the development of synchrony in layer IV, UD did not block the development of synchrony between neurons in layer IV barrels and increased synchrony within septal circuits. We conclude that changes in synchronous discharge after UD are unexpectedly different from those recorded after BD, and we speculate that this effect may be due to the driven activity from active commissural inputs arising from the contralateral hemisphere that received normal activity levels during postnatal development.
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Affiliation(s)
- Ayan Ghoshal
- Department of Psychology, Center for Integrative & Cognitive Neuroscience, Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee; Department of Pharmacology, Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, Tennessee;
| | - Brian Lustig
- Department of Psychology, Center for Integrative & Cognitive Neuroscience, Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee
| | | | - Ford Ebner
- Department of Psychology, Center for Integrative & Cognitive Neuroscience, Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee
| | - Pierre Pouget
- CM, INSERM UMRS 975, CNRS 7225, Université Pierre et Marie Curie, Paris, France
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23
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Elstrott J, Clancy KB, Jafri H, Akimenko I, Feldman DE. Cellular mechanisms for response heterogeneity among L2/3 pyramidal cells in whisker somatosensory cortex. J Neurophysiol 2014; 112:233-48. [PMID: 24740854 DOI: 10.1152/jn.00848.2013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whisker deflection evokes sparse, low-probability spiking among L2/3 pyramidal cells in rodent somatosensory cortex (S1), with spiking distributed nonuniformly between more and less responsive cells. The cellular and local circuit factors that determine whisker responsiveness across neurons are unclear. To identify these factors, we used two-photon calcium imaging and loose-seal recording to identify more and less responsive L2/3 neurons in S1 slices in vitro, during feedforward recruitment of the L2/3 network by L4 stimulation. We observed a broad gradient of spike recruitment thresholds within local L2/3 populations, with low- and high-threshold cells intermixed. This recruitment gradient was significantly correlated across different L4 stimulation sites, and between L4-evoked and whisker-evoked responses in vivo, indicating that a substantial component of responsiveness is independent of tuning to specific feedforward inputs. Low- and high-threshold L2/3 pyramidal cells differed in L4-evoked excitatory synaptic conductance and intrinsic excitability, including spike threshold and the likelihood of doublet spike bursts. A gradient of intrinsic excitability was observed across neurons. Cells that spiked most readily to L4 stimulation received the most synaptic excitation but had the lowest intrinsic excitability. Low- and high-threshold cells did not differ in dendritic morphology, passive membrane properties, or L4-evoked inhibitory conductance. Thus multiple gradients of physiological properties exist across L2/3 pyramidal cells, with excitatory synaptic input strength best predicting overall spiking responsiveness during network recruitment.
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Affiliation(s)
- Justin Elstrott
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California; and
| | - Kelly B Clancy
- Biophysics PhD Program, University of California, Berkeley, California
| | - Haani Jafri
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California; and
| | - Igor Akimenko
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California; and
| | - Daniel E Feldman
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California; and
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24
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Staiger JF, Bojak I, Miceli S, Schubert D. A gradual depth-dependent change in connectivity features of supragranular pyramidal cells in rat barrel cortex. Brain Struct Funct 2014; 220:1317-37. [PMID: 24569853 PMCID: PMC4409644 DOI: 10.1007/s00429-014-0726-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 01/31/2014] [Indexed: 01/31/2023]
Abstract
Recent experimental evidence suggests a finer genetic, structural and functional subdivision of the layers which form a cortical column. The classical layer II/III (LII/III) of rodent neocortex integrates ascending sensory information with contextual cortical information for behavioral read-out. We systematically investigated to which extent regular-spiking supragranular pyramidal neurons, located at different depths within the cortex, show different input-output connectivity patterns. Combining glutamate uncaging with whole-cell recordings and biocytin filling, we revealed a novel cellular organization of LII/III: (1) "Lower LII/III" pyramidal cells receive a very strong excitatory input from lemniscal LIV and much fewer inputs from paralemniscal LVa. They project to all layers of the home column, including a feedback projection to LIV, whereas transcolumnar projections are relatively sparse. (2) "Upper LII/III" pyramidal cells also receive their strongest input from LIV, but in addition, a very strong and dense excitatory input from LVa. They project extensively to LII/III as well as LVa and Vb of their home and neighboring columns. (3) "Middle LII/III" pyramidal cell shows an intermediate connectivity phenotype that stands in many ways in between the features described for lower versus upper LII/III. "Lower LII/III" intracolumnarly segregates and transcolumnarly integrates lemniscal information, whereas "upper LII/III" seems to integrate lemniscal with paralemniscal information. This suggests a fine-grained functional subdivision of the supragranular compartment containing multiple circuits without any obvious cytoarchitectonic, other structural or functional correlate of a laminar border in rodent barrel cortex.
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Affiliation(s)
- Jochen F. Staiger
- Institute for Neuroanatomy, University Medicine Göttingen, Kreuzbergring 36, 37075 Göttingen, Germany
| | - Ingo Bojak
- School of Systems Engineering, University of Reading, PO Box 225, Whiteknights, Reading, Berkshire RG6 6AY UK
- Donders Institute for Brain, Cognition and Behavior, Centre for Neuroscience, Radboud University Nijmegen Medical Centre, POB 9101//126, 6500 HB Nijmegen, The Netherlands
| | - Stéphanie Miceli
- Donders Institute for Brain, Cognition and Behavior, Centre for Neuroscience, Radboud University Nijmegen Medical Centre, POB 9101//126, 6500 HB Nijmegen, The Netherlands
| | - Dirk Schubert
- Donders Institute for Brain, Cognition and Behavior, Centre for Neuroscience, Radboud University Nijmegen Medical Centre, POB 9101//126, 6500 HB Nijmegen, The Netherlands
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25
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Khazipov R, Minlebaev M, Valeeva G. Early gamma oscillations. Neuroscience 2013; 250:240-52. [PMID: 23872391 DOI: 10.1016/j.neuroscience.2013.07.019] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 06/27/2013] [Accepted: 07/09/2013] [Indexed: 10/26/2022]
Abstract
Gamma oscillations have long been considered to emerge late in development. However, recent studies have revealed that gamma oscillations are transiently expressed in the rat barrel cortex during the first postnatal week, a "critical" period of sensory-dependent barrel map formation. The mechanisms underlying the generation and physiological roles of early gamma oscillations (EGOs) in the development of thalamocortical circuits will be discussed in this review. In contrast to adult gamma oscillations, synchronized through gamma-rhythmic perisomatic inhibition, EGOs are primarily driven through feedforward gamma-rhythmic excitatory input from the thalamus. The recruitment of cortical interneurons to EGOs and the emergence of feedforward inhibition are observed by the end of the first postnatal week. EGOs facilitate the precise synchronization of topographically aligned thalamic and cortical neurons. The multiple replay of sensory input during EGOs supports long-term potentiation at thalamocortical synapses. We suggest that this early form of gamma oscillations, which is mechanistically different from adult gamma oscillations, guides barrel map formation during the critical developmental period.
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Affiliation(s)
- R Khazipov
- INMED - INSERM U901, University Aix-Marseille II, Marseille, France; Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia.
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26
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Feldmeyer D, Brecht M, Helmchen F, Petersen CC, Poulet JF, Staiger JF, Luhmann HJ, Schwarz C. Barrel cortex function. Prog Neurobiol 2013. [DOI: 10.1016/j.pneurobio.2012.11.002] [Citation(s) in RCA: 257] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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27
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Egger R, Narayanan RT, Helmstaedter M, de Kock CPJ, Oberlaender M. 3D reconstruction and standardization of the rat vibrissal cortex for precise registration of single neuron morphology. PLoS Comput Biol 2012; 8:e1002837. [PMID: 23284282 PMCID: PMC3527218 DOI: 10.1371/journal.pcbi.1002837] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 10/24/2012] [Indexed: 11/19/2022] Open
Abstract
The three-dimensional (3D) structure of neural circuits is commonly studied by reconstructing individual or small groups of neurons in separate preparations. Investigation of structural organization principles or quantification of dendritic and axonal innervation thus requires integration of many reconstructed morphologies into a common reference frame. Here we present a standardized 3D model of the rat vibrissal cortex and introduce an automated registration tool that allows for precise placement of single neuron reconstructions. We (1) developed an automated image processing pipeline to reconstruct 3D anatomical landmarks, i.e., the barrels in Layer 4, the pia and white matter surfaces and the blood vessel pattern from high-resolution images, (2) quantified these landmarks in 12 different rats, (3) generated an average 3D model of the vibrissal cortex and (4) used rigid transformations and stepwise linear scaling to register 94 neuron morphologies, reconstructed from in vivo stainings, to the standardized cortex model. We find that anatomical landmarks vary substantially across the vibrissal cortex within an individual rat. In contrast, the 3D layout of the entire vibrissal cortex remains remarkably preserved across animals. This allows for precise registration of individual neuron reconstructions with approximately 30 µm accuracy. Our approach could be used to reconstruct and standardize other anatomically defined brain areas and may ultimately lead to a precise digital reference atlas of the rat brain.
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Affiliation(s)
- Robert Egger
- Digital Neuroanatomy, Max Planck Florida Institute, Jupiter, Florida, United States of America
| | - Rajeevan T. Narayanan
- Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, Amsterdam, the Netherlands
| | - Moritz Helmstaedter
- Structure of Neocortical Circuits Group, Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Christiaan P. J. de Kock
- Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, Amsterdam, the Netherlands
| | - Marcel Oberlaender
- Digital Neuroanatomy, Max Planck Florida Institute, Jupiter, Florida, United States of America
- * E-mail:
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28
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Benedetti BL, Takashima Y, Wen JA, Urban-Ciecko J, Barth AL. Differential wiring of layer 2/3 neurons drives sparse and reliable firing during neocortical development. ACTA ACUST UNITED AC 2012; 23:2690-9. [PMID: 22918982 DOI: 10.1093/cercor/bhs257] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Sensory information is transmitted with high fidelity across multiple synapses until it reaches the neocortex. There, individual neurons exhibit enormous variability in responses. The source of this diversity in output has been debated. Using transgenic mice expressing the green fluorescent protein coupled to the activity-dependent gene c-fos, we identified neurons with a history of elevated activity in vivo. Focusing on layer 4 to layer 2/3 connections, a site of strong excitatory drive at an initial stage of cortical processing, we find that fluorescently tagged neurons receive significantly greater excitatory and reduced inhibitory input compared with neighboring, unlabeled cells. Differential wiring of layer 2/3 neurons arises early in development and requires sensory input to be established. Stronger connection strength is not associated with evidence for recent synaptic plasticity, suggesting that these more active ensembles may not be generated over short time scales. Paired recordings show fosGFP+ neurons spike at lower stimulus thresholds than neighboring, fosGFP- neurons. These data indicate that differences in circuit construction can underlie response heterogeneity amongst neocortical neurons.
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Affiliation(s)
- Brett L Benedetti
- Department of Biological Sciences and Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA, USA
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29
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Ikezoe K, Tamura H, Kimura F, Fujita I. Decorrelation of sensory-evoked neuronal responses in rat barrel cortex during postnatal development. Neurosci Res 2012; 73:312-20. [PMID: 22677628 DOI: 10.1016/j.neures.2012.05.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 05/22/2012] [Accepted: 05/24/2012] [Indexed: 11/27/2022]
Abstract
The ability to detect and discriminate sensory stimuli greatly improves with age. To better understand the neural basis of perceptual development, we studied the postnatal development of sensory responses in cortical neurons. Specifically, we analyzed neuronal responses to single-whisker deflections in the posteromedial barrel subfield (PMBSF) of the rat primary somatosensory cortex. Responses of PMBSF neurons showed a long onset latency and duration in the first postnatal week, but became fast and transient over the next few weeks. Trial-by-trial variations of single neuron responses did not change systematically with age, whereas the covariation of responses across trials between neurons (noise correlation) was high on postnatal day 5-6 (P5-6), and gradually decreased with age to near zero by P30-31. Computational analyses showed that pooled responses of multiple neurons became more reliable across stimulus trials with age. The period over which these changes occurred corresponds to the period when rats develop a full set of exploratory whisking behavior. We suggest that reduced noise correlation across a population of neurons, in addition to sharpening the temporal characteristics of single neuron responses, may help improve behavioral performance.
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Affiliation(s)
- Koji Ikezoe
- Laboratory for Cognitive Neuroscience, Graduate School of Engineering Science and Graduate School of Frontier Biosciences, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
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30
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Makino H, Malinow R. Compartmentalized versus global synaptic plasticity on dendrites controlled by experience. Neuron 2012; 72:1001-11. [PMID: 22196335 DOI: 10.1016/j.neuron.2011.09.036] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2011] [Indexed: 10/14/2022]
Abstract
Synapses in the brain are continuously modified by experience, but the mechanisms are poorly understood. In vitro and theoretical studies suggest threshold-lowering interactions between nearby synapses that favor clustering of synaptic plasticity within a dendritic branch. Here, a fluorescently tagged AMPA receptor-based optical approach was developed permitting detection of single-synapse plasticity in mouse cortex. Sensory experience preferentially produced synaptic potentiation onto nearby dendritic synapses. Such clustering was significantly reduced by expression of a phospho-mutant AMPA receptor that is insensitive to threshold-lowering modulation for plasticity-driven synaptic incorporation. In contrast to experience, sensory deprivation caused homeostatic synaptic enhancement globally on dendrites. Clustered synaptic potentiation produced by experience could bind behaviorally relevant information onto dendritic subcompartments; global synaptic upscaling by deprivation could equally sensitize all dendritic regions for future synaptic input.
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Affiliation(s)
- Hiroshi Makino
- Center for Neural Circuits and Behavior, Section of Neurobiology, Division of Biology and Department of Neuroscience, University of California, San Diego, La Jolla, CA 92093, USA
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31
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House DRC, Elstrott J, Koh E, Chung J, Feldman DE. Parallel regulation of feedforward inhibition and excitation during whisker map plasticity. Neuron 2012; 72:819-31. [PMID: 22153377 DOI: 10.1016/j.neuron.2011.09.008] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2011] [Indexed: 01/01/2023]
Abstract
Sensory experience drives robust plasticity of sensory maps in cerebral cortex, but the role of inhibitory circuits in this process is not fully understood. We show that classical deprivation-induced whisker map plasticity in layer 2/3 (L2/3) of rat somatosensory (S1) cortex involves robust weakening of L4-L2/3 feedforward inhibition. This weakening was caused by reduced L4 excitation onto L2/3 fast-spiking (FS) interneurons, which mediate sensitive feedforward inhibition and was partially offset by strengthening of unitary FS to L2/3 pyramidal cell synapses. Weakening of feedforward inhibition paralleled the known weakening of feedforward excitation. As a result, mean excitation-inhibition balance and timing onto L2/3 pyramidal cells were preserved. Thus, reduced feedforward inhibition is a covert compensatory process that can maintain excitatory-inhibitory balance during classical deprivation-induced Hebbian map plasticity.
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Affiliation(s)
- David R C House
- Neuroscience Ph.D. Program, University of California, San Diego, La Jolla, CA 92093, USA
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32
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Zhang Z, Sun QQ. Development of NMDA NR2 subunits and their roles in critical period maturation of neocortical GABAergic interneurons. Dev Neurobiol 2011; 71:221-45. [PMID: 20936660 DOI: 10.1002/dneu.20844] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The goals of this research are to (1) determine the changes in the composition of NMDA receptor (NMDAR) subunits in GABAergic interneurons during critical period (CP); and (2) test the effect of chronic blockage of specific NR2 subunits on the maturation of specific GABAergic interneurons. Our data demonstrate that: (1) The amplitude of NMDAR mediated EPSCs (EPSCs(NMDAR) ) was significantly larger in the postCP group. (2) The coefficient of variation (CV), τ(decay) and half-width of EPSCs(NMDAR) were significantly larger in the preCP group. (3) A leftward shift in the half-activation voltages in the postCP vs. preCP group. (4) Using subunit-specific antagonists, we found a postnatal shift in NR2 composition towards more NR2A mediated EPSCs(NMDAR) . These changes occurred within a two-day narrow window of CP and were similar between fast-spiking (FS) and regular spiking (RSNP) interneurons. (5) Chronic blockage of NR2A, but not NR2B, decreased the expression of parvalbumin (PV), but not other calcium binding proteins in layer 2/3 and 4 of barrel cortex. (6) Chronic blockage of NR2A selectively affected the maturation of IPSCs mediated by FS cells. In summary, we have reported, for the first time, developmental changes in the molecular composition of NMDA NR2 subunits in interneurons during CP, and the effects of chronic blockage of NR2A but not NR2B on PV expression and inhibitory synaptic transmission from FS cells. These results support an important role of NR2A subunits in developmental plasticity of fast-spiking GABAergic circuits during CP.
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Affiliation(s)
- Zhi Zhang
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071, USA
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33
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Kaliszewska A, Bijata M, Kaczmarek L, Kossut M. Experience-Dependent Plasticity of the Barrel Cortex in Mice Observed with 2-DG Brain Mapping and c-Fos: Effects of MMP-9 KO. Cereb Cortex 2011; 22:2160-70. [DOI: 10.1093/cercor/bhr303] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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34
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Macroscopic Connection Of Rat Insular Cortex: Anatomical Bases Underlying Its Physiological Functions. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2011; 97:285-303. [DOI: 10.1016/b978-0-12-385198-7.00011-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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35
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Geometric and functional architecture of visceral sensory microcircuitry. Brain Struct Funct 2010; 216:17-30. [PMID: 21153904 PMCID: PMC3040306 DOI: 10.1007/s00429-010-0294-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 11/23/2010] [Indexed: 12/24/2022]
Abstract
Is microcircuit wiring designed deterministically or probabilistically? Does geometric architecture predict functional dynamics of a given neuronal microcircuit? These questions were addressed in the visceral sensory microcircuit of the caudal nucleus of the tractus solitarius (NTS), which is generally thought to be homogeneous rather than laminar in cytoarchitecture. Using in situ hybridization histochemistry and whole-cell patch clamp recordings followed by neuronal reconstruction with biocytin filling, anatomical and functional organization of NTS microcircuitry was quantified to determine associative relationships. Morphologic and chemical features of NTS neurons displayed different patterns of process arborization and sub-nuclear localization according to neuronal types: smaller cells featured presynaptic local axons and GABAergic cells were aggregated specifically within the ventral NTS. The results suggested both a laminar organization and a spatial heterogeneity of NTS microcircuit connectivity. Geometric analysis of pre- and postsynaptic axodendritic arbor overlap of reconstructed neurons (according to parent somal distance) confirmed a heterogeneity of microcircuit connectivity that could underlie differential functional dynamics along the dorsoventral axis. Functional dynamics in terms of spontaneous and evoked postsynaptic current patterns behaved in a strongly location-specific manner according to the geometric dimension, suggesting a spatial laminar segregation of neuronal populations: a dorsal group of high excitation and a ventral group of balanced excitation and inhibition. Recurrent polysynaptic activity was also noted in a subpopulation of the ventral group. Such geometric and functional laminar organization seems to provide the NTS microcircuit with both reverberation capability and a differentiated projection system for appropriate computation of visceral sensory information.
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36
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Zhang Z, Jiao YY, Sun QQ. Developmental maturation of excitation and inhibition balance in principal neurons across four layers of somatosensory cortex. Neuroscience 2010; 174:10-25. [PMID: 21115101 DOI: 10.1016/j.neuroscience.2010.11.045] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 10/27/2010] [Accepted: 11/21/2010] [Indexed: 11/29/2022]
Abstract
In adult cortices, the ratio of excitatory and inhibitory conductances (E/I ratio) is presumably balanced across a wide range of stimulus conditions. However, it is unknown how the E/I ratio is postnatally regulated, when the strength of synapses are rapidly changing. Yet, understanding of such a process is critically important, because there are numerous neuropsychological disorders, such as autism, epilepsy and schizophrenia, associated with disturbed E/I balances. Here we directly measured the E/I ratio underlying locally induced synaptic conductances in principal neurons from postnatal day 8 (P8) through 60. We found that (1) within each developmental period, the E/I ratio across four major cortical layers was maintained at a similar value under wide range of stimulation intensities; and (2) there was a rapid developmental decrease in the E/I ratio, which occurred within a sensitive period between P8 to P18 with exception of layer II/III. By comparing the excitatory and inhibitory conductances, as well as key synaptic protein expressions, we found a net increase in the number and strength of inhibitory, but not excitatory synapses, is responsible for the developmental decrease in the E/I ratio in the barrel cortex. The inhibitory markers were intrinsically co-regulated, gave rise to a sharp increase in the inhibitory conductance from P8 to P18. These results suggest that the tightly regulated E/I ratios in adults cortex is a result of drastic changes in relative weight of inhibitory but not excitatory synapses during critical period, and the local inhibitory structural changes are the underpinning of altered E/I ratio across postnatal development.
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Affiliation(s)
- Z Zhang
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
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37
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Budd JML, Kovács K, Ferecskó AS, Buzás P, Eysel UT, Kisvárday ZF. Neocortical axon arbors trade-off material and conduction delay conservation. PLoS Comput Biol 2010; 6:e1000711. [PMID: 20300651 PMCID: PMC2837396 DOI: 10.1371/journal.pcbi.1000711] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 02/08/2010] [Indexed: 01/04/2023] Open
Abstract
The brain contains a complex network of axons rapidly communicating information between billions of synaptically connected neurons. The morphology of individual axons, therefore, defines the course of information flow within the brain. More than a century ago, Ramón y Cajal proposed that conservation laws to save material (wire) length and limit conduction delay regulate the design of individual axon arbors in cerebral cortex. Yet the spatial and temporal communication costs of single neocortical axons remain undefined. Here, using reconstructions of in vivo labelled excitatory spiny cell and inhibitory basket cell intracortical axons combined with a variety of graph optimization algorithms, we empirically investigated Cajal's conservation laws in cerebral cortex for whole three-dimensional (3D) axon arbors, to our knowledge the first study of its kind. We found intracortical axons were significantly longer than optimal. The temporal cost of cortical axons was also suboptimal though far superior to wire-minimized arbors. We discovered that cortical axon branching appears to promote a low temporal dispersion of axonal latencies and a tight relationship between cortical distance and axonal latency. In addition, inhibitory basket cell axonal latencies may occur within a much narrower temporal window than excitatory spiny cell axons, which may help boost signal detection. Thus, to optimize neuronal network communication we find that a modest excess of axonal wire is traded-off to enhance arbor temporal economy and precision. Our results offer insight into the principles of brain organization and communication in and development of grey matter, where temporal precision is a crucial prerequisite for coincidence detection, synchronization and rapid network oscillations. Within the grey matter of cerebral cortex is a complex network formed by a dense tangle of individual branching axons mostly of cortical origin. Yet remarkably when presented with a barrage of complex, noisy sensory stimuli this convoluted network architecture computes accurately and rapidly. How does such a highly interconnected though jumbled forest of axonal trees process vital information so quickly? Pioneering neuroscientist Ramón y Cajal thought the size and shape of individual neurons was governed by simple rules to save cellular material and to reduce signal conduction delay. In this study, we investigated how these rules applied to whole axonal trees in neocortex by comparing their 3D structure to equivalent artificial arbors optimized for these rules. We discovered that neocortical axonal trees achieve a balance between these two rules so that a little more cellular material than necessary was used to substantially reduce conduction delays. Importantly, we suggest the nature of arbor branching balances time and material so that neocortical axons may communicate with a high degree of temporal precision, enabling accurate and rapid computation within local cortical networks. This approach could be applied to other neural structures to better understand the functional principles of brain design.
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Affiliation(s)
- Julian M L Budd
- School of Informatics, University of Sussex, Brighton, United Kingdom.
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38
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Quairiaux C, Sizonenko SV, Mégevand P, Michel CM, Kiss JZ. Functional deficit and recovery of developing sensorimotor networks following neonatal hypoxic-ischemic injury in the rat. Cereb Cortex 2010; 20:2080-91. [PMID: 20051355 DOI: 10.1093/cercor/bhp281] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Neonatal hypoxia-ischemia (HI) is the most important cause of brain injury in the newborn. Here we studied structural alterations and functional perturbations of developing large-scale sensorimotor cortical networks in a rat model of moderate HI at postnatal day 3 (P3). At the morphological level, HI led to a disorganized barrel pattern in the somatosensory cortex without detectable histological changes in the motor cortex. Functional effects were addressed by means of epicranial mapping of somatosensory-evoked potentials (SEPs) during the postischemic recovery period. At P10, SEPs were immature and evoked activity was almost restricted to the somatosensory and motor cortices of the contralateral hemisphere. Peak and topographic analyses of epicranial potentials revealed that responses were profoundly depressed in both sensory and motor areas of HI-lesioned animals. At the end of the postnatal period at P21, responses involved networks in both hemispheres. SEP amplitude was still depressed in the injured sensory region, but it completely recovered in the motor area. These results suggest a process of large-scale network plasticity in sensorimotor circuits after perinatal ischemic injury. The model provides new perspectives for investigating the temporal and spatial characteristics of the recovery process following HI and eventually developing therapeutic interventions.
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Affiliation(s)
- Charles Quairiaux
- Faculty of Medicine, Department of Fundamental Neurosciences, University of Geneva, 1211 Geneva, Switzerland.
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39
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Endocannabinoid signaling is required for development and critical period plasticity of the whisker map in somatosensory cortex. Neuron 2009; 64:537-49. [PMID: 19945395 DOI: 10.1016/j.neuron.2009.10.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2009] [Indexed: 01/29/2023]
Abstract
Type 1 cannabinoid (CB1) receptors mediate widespread synaptic plasticity, but how this contributes to systems-level plasticity and development in vivo is unclear. We tested whether CB1 signaling is required for development and plasticity of the whisker map in rat somatosensory cortex. Treatment with the CB1 antagonist AM251 during an early critical period for layer (L) 2/3 development (beginning postnatal day [P] 12-16) disrupted whisker map development, leading to inappropriate whisker tuning in L2/3 column edges and a blurred map. Early AM251 treatment also prevented experience-dependent plasticity in L2/3, including deprivation-induced synapse weakening and weakening of deprived whisker responses. CB1 blockade after P25 did not disrupt map development or plasticity. AM251 had no acute effect on sensory-evoked spiking and only modestly affected field potentials, suggesting that plasticity effects were not secondary to gross activity changes. These findings implicate CB1-dependent plasticity in systems-level development and early postnatal plasticity of the whisker map.
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40
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Feldmeyer D, Radnikow G. Developmental alterations in the functional properties of excitatory neocortical synapses. J Physiol 2009; 587:1889-96. [PMID: 19273572 DOI: 10.1113/jphysiol.2009.169458] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In the neocortex, most excitatory, glutamatergic synapses are established during the first 4-5 weeks after birth. During this period profound changes in the properties of synaptic transmission occur. Excitatory postsynaptic potentials (EPSPs) at immature synaptic connections are profoundly and progressively reduced in response to moderate to high frequency (5-100 Hz) stimulation. With maturation, this frequency-dependent depression becomes progressively weaker and may eventually transform into a weak to moderate EPSP facilitation. In parallel to changes in the short-term plasticity, a reduction in the synaptic reliability occurs at most glutamatergic neocortical synapses: immature synapses show a high probability of neurotransmitter release as indicated by their low failure rate and small EPSP amplitude variation. This high reliability is reduced in mature synapses, which show considerably higher failure rates and more variable EPSP amplitudes. During early neocortical development synaptic vesicle pools are not yet fully differentiated and their replenishment may be slow, thus resulting in EPSP amplitude depression. The decrease in the probability of neurotransmitter release may be the result of an altered Ca(2+) control in the presynaptic terminal with a reduced Ca(2+) influx and/or a higher Ca(2+) buffering capacity. This may lead to a lower synaptic reliability and a weaker short-term synaptic depression with maturation.
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Affiliation(s)
- Dirk Feldmeyer
- Research Centre Jülich, Institute for Neuroscience and Medicine, INM-2, Juelich, Germany.
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41
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Bender KJ, Trussell LO. Axon initial segment Ca2+ channels influence action potential generation and timing. Neuron 2009; 61:259-71. [PMID: 19186168 DOI: 10.1016/j.neuron.2008.12.004] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 10/30/2008] [Accepted: 12/01/2008] [Indexed: 12/31/2022]
Abstract
Although action potentials are typically generated in the axon initial segment (AIS), the timing and pattern of action potentials are thought to depend on inward current originating in somatodendritic compartments. Using two-photon imaging, we show that T- and R-type voltage-gated Ca(2+) channels are colocalized with Na(+) channels in the AIS of dorsal cochlear nucleus interneurons and that activation of these Ca(2+) channels is essential to the generation and timing of action potential bursts known as complex spikes. During complex spikes, where Na(+)-mediated spikelets fire atop slower depolarizing conductances, selective block of AIS Ca(2+) channels delays spike timing and raises spike threshold. Furthermore, AIS Ca(2+) channel block can decrease the number of spikelets within a complex spike and can even block single, simple spikes. Similar results were found in cortex and cerebellum. Thus, voltage-gated Ca(2+) channels at the site of spike initiation play a key role in generating and shaping spike bursts.
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Affiliation(s)
- Kevin J Bender
- Vollum Institute and Oregon Hearing Research Center, Oregon Health and Science University, Portland, OR 97239, USA.
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42
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Bureau I. The development of cortical columns: role of Fragile X mental retardation protein. J Physiol 2009; 587:1897-901. [PMID: 19139042 DOI: 10.1113/jphysiol.2008.167155] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Neuronal circuits in the brain are complex and precise. Here, I review aspects of the development of cortical columns in the rodent barrel cortex, focusing on the anatomical and functional data describing the maturation of ascending glutamatergic circuits. Projections from layer 4 to layer 3 develop into cortical columns with little macroscopic refinement. Depriving animals of normal sensory experience induces long-term synaptic depression but does not perturb this pattern of development. Mouse models of mental retardation can help us understand the mechanisms of development of cortical columns. Fmr1 knock-out (ko) mice, a model for Fragile X syndrome, lack Fragile X mental retardation protein (FMRP), a suppressor of translation present in synapses. Because FMRP expression is stimulated by neuronal activity, Fmr1-ko mice provide a model to survey the role of sensory input in brain development. Layer 4 to layer 3 projections are altered in multiple ways in the young mutant mice: connection rate is low and layer 4 cell axons are spatially diffuse. Sensory deprivation rescues the connection rate phenotype. The interaction of FMRP and neuronal activity in the development of cortical circuits is discussed.
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43
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Kobayashi M, Hamada T, Kogo M, Yanagawa Y, Obata K, Kang Y. Developmental profile of GABAA-mediated synaptic transmission in pyramidal cells of the somatosensory cortex. Eur J Neurosci 2008; 28:849-61. [DOI: 10.1111/j.1460-9568.2008.06401.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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44
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Drew PJ, Feldman DE. Intrinsic signal imaging of deprivation-induced contraction of whisker representations in rat somatosensory cortex. ACTA ACUST UNITED AC 2008; 19:331-48. [PMID: 18515797 DOI: 10.1093/cercor/bhn085] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In classical sensory cortical map plasticity, the representation of deprived or underused inputs contracts within cortical sensory maps, whereas spared inputs expand. Expansion of spared inputs occurs preferentially into nearby cortical columns representing temporally correlated spared inputs, suggesting that expansion involves correlation-based learning rules at cross-columnar synapses. It is unknown whether deprived representations contract in a similar anisotropic manner, which would implicate similar learning rules and sites of plasticity. We briefly deprived D-row whiskers in 20-day-old rats, so that each deprived whisker had deprived (D-row) and spared (C- and E-row) neighbors. Intrinsic signal optical imaging revealed that D-row deprivation weakened and contracted the functional representation of deprived D-row whiskers in L2/3 of somatosensory (S1) cortex. Spared whisker representations did not strengthen or expand, indicating that D-row deprivation selectively engages the depression component of map plasticity. Contraction of deprived whisker representations was spatially uniform, with equal withdrawal from spared and deprived neighbors. Single-unit electrophysiological recordings confirmed these results, and showed substantial weakening of responses to deprived whiskers in layer 2/3 of S1, and modest weakening in L4. The observed isotropic contraction of deprived whisker representations during D-row deprivation is consistent with plasticity at intracolumnar, rather than cross-columnar, synapses.
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Affiliation(s)
- Patrick J Drew
- Section of Neurobiology, Division of Biological Science, University of California, San Diego, La Jolla, CA 92093-0357, USA
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45
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Wallace DJ, Sakmann B. Plasticity of representational maps in somatosensory cortex observed by in vivo voltage-sensitive dye imaging. ACTA ACUST UNITED AC 2007; 18:1361-73. [PMID: 17921458 DOI: 10.1093/cercor/bhm168] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We investigated the effect of selective whisker trimming on the development of the cortical representation of a whisker deflection in layer 2/3 of rat somatosensory cortex using in vivo voltage-sensitive dye (vsd) imaging. Responses to deflection of D-row whiskers were recorded after trimming of A-row, B-row, and C-row whiskers, referred to as DE pairing, during postnatal development. Animals DE paired from postnatal day (p) 7 to p17 had a significant bias in the spread of the vsd signal, favoring spread toward the concomitantly nondeprived E-row columns. This resulted primarily from a strong decrease in signal spreading into the deprived C-row columns. In contrast, signal spread in control littermates was approximately symmetrical. DE pairing failed to elicit significant changes when begun after p14, thus defining a critical period for this phenomenon. The results suggest that sensory deprivation in this model results in lower connectivity being established between nondeprived columns and adjacent deprived ones.
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Affiliation(s)
- Damian J Wallace
- Department of Cell Physiology, Max Planck Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Germany.
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46
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Melzer P, Mineo L, Ebner FF. Optic nerve transection affects development and use-dependent plasticity in neocortex of the rat: Quantitative acetylcholinesterase imaging. Brain Res 2007; 1139:68-84. [PMID: 17280650 DOI: 10.1016/j.brainres.2006.12.080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Revised: 12/04/2006] [Accepted: 12/14/2006] [Indexed: 11/15/2022]
Abstract
We investigated the effects of neonatal optic nerve transection on cortical acetylcholinesterase (AChE) activity in hooded rats during postnatal development and following behavioral manipulation after weaning. AChE reaction product was quantified on digitized images of histochemically stained sections in layer IV of primary somatic sensory, primary visual and visual association cortex. Rats with optic nerve transection were compared to sham-operated littermates. In all cortical regions of both types of animal, AChE reaction product was increased to peak 2 weeks after birth and decreased thereafter, reaching adult levels at the end of the third postnatal week. During postnatal development, reaction product in primary visual cortex was lower in rats deprived of retinal input than in sham-operated littermates and the area delineated by reaction product was smaller. However, optic nerve transection did not modify the time course of postnatal development or statistically significantly diminish adult levels of AChE activity. Behavioral manipulations after weaning statistically significantly increased enzyme activity in sham-operated rats in all cortical areas examined. Compared with cage rearing, training in a discrimination task with food reward had a greater impact than environmental enrichment. By contrast, in the rats with optic nerve transection enrichment and training resulted in statistically significantly increased AChE activity only in lateral visual association cortex. Our findings provide evidence for intra- and supramodal influences of the neonatal removal of retinal input on neural activity- and use-dependent modifications of cortical AChE activity. The laminar distribution of the AChE reaction product suggests that the observed changes in AChE activity were mainly related to cholinergic basal forebrain afferents. These afferents may facilitate the stabilization of transient connections between the somatic sensory and the visual pathway.
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Affiliation(s)
- Peter Melzer
- Deparment of Psychology, Vanderbilt University, 301 Wilson Hall, 111 21st Ave. S., Nashville, Tennessee 37203, USA.
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Deshmukh S, Onozuka K, Bender KJ, Bender VA, Lutz B, Mackie K, Feldman DE. Postnatal development of cannabinoid receptor type 1 expression in rodent somatosensory cortex. Neuroscience 2007; 145:279-87. [PMID: 17210229 PMCID: PMC1850104 DOI: 10.1016/j.neuroscience.2006.11.033] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 11/17/2006] [Accepted: 11/20/2006] [Indexed: 11/19/2022]
Abstract
Endocannabinoids are powerful modulators of synaptic transmission that act on presynaptic cannabinoid receptors. Cannabinoid receptor type 1 (CB1) is the dominant receptor in the CNS, and is present in many brain regions, including sensory cortex. To investigate the potential role of CB1 receptors in cortical development, we examined the developmental expression of CB1 in rodent primary somatosensory (barrel) cortex, using immunohistochemistry with a CB1-specific antibody. We found that before postnatal day (P) 6, CB1 receptor staining was present exclusively in the cortical white matter, and that CB1 staining appeared in the gray matter between P6 and P20 in a specific laminar pattern. CB1 staining was confined to axons, and was most prominent in cortical layers 2/3, 5a, and 6. CB1 null (-/-) mice showed altered anatomical barrel maps in layer 4, with enlarged inter-barrel septa, but normal barrel size. These results indicate that CB1 receptors are present in early postnatal development and influence development of sensory maps.
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Affiliation(s)
- Suvarna Deshmukh
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357
| | - Kaori Onozuka
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357
| | - Kevin J. Bender
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357
| | - Vanessa A. Bender
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357
| | - Beat Lutz
- Department of Physiological Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 6, 55099 Mainz, Germany
| | - Ken Mackie
- Department of Anesthesiology, University of Washington School of Medicine, Seattle, WA 98195-6540
| | - Daniel E. Feldman
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357
- Corresponding author: phone 858-822-4271, fax 858-534-7309,
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Andermann ML, Moore CI. A somatotopic map of vibrissa motion direction within a barrel column. Nat Neurosci 2006; 9:543-51. [PMID: 16547511 DOI: 10.1038/nn1671] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 02/23/2006] [Indexed: 11/09/2022]
Abstract
Most mammals possess high-resolution visual perception, with primary visual cortices containing fine-scale, inter-related feature representations (for example, orientation and ocular dominance). Rats lack precise vision, but their vibrissa sensory system provides a precise tactile modality, including vibrissa-related 'barrel' columns in primary somatosensory cortex. Here, we examined the subcolumnar organization of direction preference and somatotopy using a new omni-directional, multi-vibrissa stimulator. We discovered a direction map that was systematically linked to somatotopy, such that neurons were tuned for motion toward their preferred surround vibrissa. This sub-barrel column direction map demonstrated an emergent refinement from layer IV to layer II/III. These data suggest that joint processing of multiple sensory features is a common property of high-resolution sensory systems.
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Affiliation(s)
- Mark L Andermann
- Harvard Program in Biophysics, Medical School Campus, Building C-2 Room 122, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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Larsen DD, Callaway EM. Development of layer-specific axonal arborizations in mouse primary somatosensory cortex. J Comp Neurol 2006; 494:398-414. [PMID: 16320250 PMCID: PMC4651208 DOI: 10.1002/cne.20754] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In the developing neocortex, pyramidal neurons use molecular cues to form axonal arbors selectively in the correct layers. Despite the utility of mice for molecular and genetic studies, little work has been done on the development of layer-specific axonal arborizations of pyramidal neurons in mice. We intracellularly labeled and reconstructed the axons of layer 2/3 and layer 5 pyramidal neurons in slices of primary somatosensory cortex from C57Bl6 mice on postnatal days 7-21. For all neurons studied, the development of the axonal arborizations in mice follows a pattern similar to that seen in other species; laminar specificity of the earliest axonal branches is similar to that of mature animals. At P7, pyramidal neurons are very simple, having only a main descending axon and few primary branches. Between P7 and P10, there is a large increase in the total number of axonal branches, and axons continue to increase in complexity and total length from P10 to P21. Unlike observations in ferrets, cats, and monkeys, two types of layer 2/3 pyramidal neurons are present in both mature and developing mice; cells in superficial layer 2/3 lack axonal arbors in layer 4, and cells close to the layer 4 border have substantial axonal arbors within layer 4. We also describe axonal and dendritic arborization patterns of three pyramidal cell types in layer 5. The axons of tall-tufted layer 5 pyramidal neurons arborize almost exclusively within deep layers while tall-simple, and short layer 5 pyramidal neurons also project axons to superficial layers.
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Affiliation(s)
- DeLaine D Larsen
- Systems Neurobiology Laboratories, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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Abstract
Sensory maps in neocortex are adaptively altered to reflect recent experience and learning. In somatosensory cortex, distinct patterns of sensory use or disuse elicit multiple, functionally distinct forms of map plasticity. Diverse approaches—genetics, synaptic and in vivo physiology, optical imaging, and ultrastructural analysis—suggest a distributed model in which plasticity occurs at multiple sites in the cortical circuit with multiple cellular/synaptic mechanisms and multiple likely learning rules for plasticity. This view contrasts with the classical model in which the map plasticity reflects a single Hebbian process acting at a small set of cortical synapses.
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Affiliation(s)
- Daniel E Feldman
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, Room 0357, La Jolla, CA 92093, USA.
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