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Gehr C, Sibille J, Kremkow J. Retinal input integration in excitatory and inhibitory neurons in the mouse superior colliculus in vivo. eLife 2023; 12:RP88289. [PMID: 37682267 PMCID: PMC10491433 DOI: 10.7554/elife.88289] [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] [Indexed: 09/09/2023] Open
Abstract
The superior colliculus (SC) is a midbrain structure that receives inputs from retinal ganglion cells (RGCs). The SC contains one of the highest densities of inhibitory neurons in the brain but whether excitatory and inhibitory SC neurons differentially integrate retinal activity in vivo is still largely unknown. We recently established a recording approach to measure the activity of RGCs simultaneously with their postsynaptic SC targets in vivo, to study how SC neurons integrate RGC activity. Here, we employ this method to investigate the functional properties that govern retinocollicular signaling in a cell type-specific manner by identifying GABAergic SC neurons using optotagging in VGAT-ChR2 mice. Our results demonstrate that both excitatory and inhibitory SC neurons receive comparably strong RGC inputs and similar wiring rules apply for RGCs innervation of both SC cell types, unlike the cell type-specific connectivity in the thalamocortical system. Moreover, retinal activity contributed more to the spiking activity of postsynaptic excitatory compared to inhibitory SC neurons. This study deepens our understanding of cell type-specific retinocollicular functional connectivity and emphasizes that the two major brain areas for visual processing, the visual cortex and the SC, differently integrate sensory afferent inputs.
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Affiliation(s)
- Carolin Gehr
- Neuroscience Research Center, Charité-Universitätsmedizin BerlinBerlinGermany
- Bernstein Center for Computational Neuroscience BerlinBerlinGermany
- Institute for Theoretical Biology, Humboldt-Universität zu BerlinBerlinGermany
- Einstein Center for Neurosciences BerlinBerlinGermany
| | - Jeremie Sibille
- Neuroscience Research Center, Charité-Universitätsmedizin BerlinBerlinGermany
- Bernstein Center for Computational Neuroscience BerlinBerlinGermany
- Institute for Theoretical Biology, Humboldt-Universität zu BerlinBerlinGermany
- Einstein Center for Neurosciences BerlinBerlinGermany
| | - Jens Kremkow
- Neuroscience Research Center, Charité-Universitätsmedizin BerlinBerlinGermany
- Bernstein Center for Computational Neuroscience BerlinBerlinGermany
- Institute for Theoretical Biology, Humboldt-Universität zu BerlinBerlinGermany
- Einstein Center for Neurosciences BerlinBerlinGermany
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2
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Bereshpolova Y, Hei X, Alonso JM, Swadlow HA. Three rules govern thalamocortical connectivity of fast-spike inhibitory interneurons in the visual cortex. eLife 2020; 9:60102. [PMID: 33289630 PMCID: PMC7723404 DOI: 10.7554/elife.60102] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/30/2020] [Indexed: 11/13/2022] Open
Abstract
Some cortical neurons receive highly selective thalamocortical (TC) input, but others do not. Here, we examine connectivity of single thalamic neurons (lateral geniculate nucleus, LGN) onto putative fast-spike inhibitory interneurons in layer 4 of rabbit visual cortex. We show that three 'rules' regulate this connectivity. These rules concern: (1) the precision of retinotopic alignment, (2) the amplitude of the postsynaptic local field potential elicited near the interneuron by spikes of the LGN neuron, and (3) the interneuron's response latency to strong, synchronous LGN input. We found that virtually all first-order fast-spike interneurons receive input from nearly all LGN axons that synapse nearby, regardless of their visual response properties. This was not the case for neighboring regular-spiking neurons. We conclude that profuse and highly promiscuous TC inputs to layer-4 fast-spike inhibitory interneurons generate response properties that are well-suited to mediate a fast, sensitive, and broadly tuned feed-forward inhibition of visual cortical excitatory neurons.
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Affiliation(s)
- Yulia Bereshpolova
- Department of Psychological Sciences, University of Connecticut, Storrs, United States
| | - Xiaojuan Hei
- Department of Psychological Sciences, University of Connecticut, Storrs, United States
| | - Jose-Manuel Alonso
- Department of Psychological Sciences, University of Connecticut, Storrs, United States.,Department of Biological and Vision Sciences, State University of New York College of Optometry, New York, United States
| | - Harvey A Swadlow
- Department of Psychological Sciences, University of Connecticut, Storrs, United States.,Department of Biological and Vision Sciences, State University of New York College of Optometry, New York, United States
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3
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Mukherjee A, Bajwa N, Lam NH, Porrero C, Clasca F, Halassa MM. Variation of connectivity across exemplar sensory and associative thalamocortical loops in the mouse. eLife 2020; 9:e62554. [PMID: 33103997 PMCID: PMC7644223 DOI: 10.7554/elife.62554] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 10/23/2020] [Indexed: 12/22/2022] Open
Abstract
The thalamus engages in sensation, action, and cognition, but the structure underlying these functions is poorly understood. Thalamic innervation of associative cortex targets several interneuron types, modulating dynamics and influencing plasticity. Is this structure-function relationship distinct from that of sensory thalamocortical systems? Here, we systematically compared function and structure across a sensory and an associative thalamocortical loop in the mouse. Enhancing excitability of mediodorsal thalamus, an associative structure, resulted in prefrontal activity dominated by inhibition. Equivalent enhancement of medial geniculate excitability robustly drove auditory cortical excitation. Structurally, geniculate axons innervated excitatory cortical targets in a preferential manner and with larger synaptic terminals, providing a putative explanation for functional divergence. The two thalamic circuits also had distinct input patterns, with mediodorsal thalamus receiving innervation from a diverse set of cortical areas. Altogether, our findings contribute to the emerging view of functional diversity across thalamic microcircuits and its structural basis.
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Affiliation(s)
- Arghya Mukherjee
- McGovern Institute for Brain ResearchCambridgeUnited States
- Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Navdeep Bajwa
- McGovern Institute for Brain ResearchCambridgeUnited States
- Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Norman H Lam
- McGovern Institute for Brain ResearchCambridgeUnited States
- Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - César Porrero
- Department of Anatomy and Neuroscience, School of Medicine, Autónoma de Madrid UniversityMadridSpain
| | - Francisco Clasca
- Department of Anatomy and Neuroscience, School of Medicine, Autónoma de Madrid UniversityMadridSpain
| | - Michael M Halassa
- McGovern Institute for Brain ResearchCambridgeUnited States
- Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
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4
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Lourenço J, Koukouli F, Bacci A. Synaptic inhibition in the neocortex: Orchestration and computation through canonical circuits and variations on the theme. Cortex 2020; 132:258-280. [PMID: 33007640 DOI: 10.1016/j.cortex.2020.08.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/28/2020] [Accepted: 08/31/2020] [Indexed: 12/15/2022]
Abstract
The neocortex plays a crucial role in all basic and abstract cognitive functions. Conscious mental processes are achieved through a correct flow of information within and across neocortical networks, whose particular activity state results from a tight balance between excitation and inhibition. The proper equilibrium between these indissoluble forces is operated with multiscale organization: along the dendro-somatic axis of single neurons and at the network level. Fast synaptic inhibition is assured by a multitude of inhibitory interneurons. During cortical activities, these cells operate a finely tuned division of labor that is epitomized by their detailed connectivity scheme. Recent results combining the use of mouse genetics, cutting-edge optical and neurophysiological approaches have highlighted the role of fast synaptic inhibition in driving cognition-related activity through a canonical cortical circuit, involving several major interneuron subtypes and principal neurons. Here we detail the organization of this cortical blueprint and we highlight the crucial role played by different neuron types in fundamental cortical computations. In addition, we argue that this canonical circuit is prone to many variations on the theme, depending on the resolution of the classification of neuronal types, and the cortical area investigated. Finally, we discuss how specific alterations of distinct inhibitory circuits can underlie several devastating brain diseases.
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Affiliation(s)
- Joana Lourenço
- Sorbonne Université, Institut Du Cerveau-Paris Brain Institute-ICM, Inserm U1127, CNRS UMR 7225, 47 Boulevard de L'Hôpital, 75013, Paris, France.
| | - Fani Koukouli
- Sorbonne Université, Institut Du Cerveau-Paris Brain Institute-ICM, Inserm U1127, CNRS UMR 7225, 47 Boulevard de L'Hôpital, 75013, Paris, France
| | - Alberto Bacci
- Sorbonne Université, Institut Du Cerveau-Paris Brain Institute-ICM, Inserm U1127, CNRS UMR 7225, 47 Boulevard de L'Hôpital, 75013, Paris, France.
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5
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Molotchnikoff S, Bharmauria V, Bachatene L, Chanauria N, Maya-Vetencourt JF. The function of connectomes in encoding sensory stimuli. Prog Neurobiol 2019; 181:101659. [PMID: 31255701 DOI: 10.1016/j.pneurobio.2019.101659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 05/06/2019] [Accepted: 06/24/2019] [Indexed: 12/27/2022]
Abstract
The enormous number of neurons and the massive sum of connecting fibers linking them make the neural processes of encoding sensory signals extraordinarily complex, and this challenge is far from being elucidated. Simply stated, for the present paper, the question is - how does the brain encode complex images? Our proposal argues that modulation of strengths of functional relationships between firing neurons in relation to an input results in the formation of stimulus-salient functional connectomes. This type of connection/coupling strength is computed by performing cross correlograms (CCG) of spike trains between simultaneously firing cells. Significantly, the strength is dependent upon stimuli characteristics, inferring that cells may join or leave particular ensembles, thus creating signature emergent connectomes for different images, thereby, allowing their discrimination. We observed in an ensemble that functionally connected cells exhibited synergistic excitatory activity, increased coherence, and augmented gamma oscillations within a window-of-opportunity contrasting with unconnected neighboring neuronal companions. We suggest that investigating and revealing such stimulus-salient emergent connectomes is a realistic and promising pursuit toward answering how the brain processes complex images.
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Affiliation(s)
- Stéphane Molotchnikoff
- Dépt de sciences biologiques Université de Montréal, Canada; Dépt de génie électrique et génie informatique, Université de Sherbrooke, Sherbrooke, Canada.
| | | | - Lyes Bachatene
- Dépt de sciences biologiques Université de Montréal, Canada
| | | | - Jose Fernando Maya-Vetencourt
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy; IRCCS, Ospedale Policlinico San Martino, Genova, Italy; Department of Biology, University of Pisa, Pisa, Italy
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6
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Electrophysiological monitoring of inhibition in mammalian species, from rodents to humans. Neurobiol Dis 2019; 130:104500. [PMID: 31195126 DOI: 10.1016/j.nbd.2019.104500] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 05/31/2019] [Accepted: 06/06/2019] [Indexed: 01/20/2023] Open
Abstract
GABAergic interneurons constitute a highly diverse family of neurons that play a critical role in cortical functions. Due to their prominent role in cortical network dynamics, genetic, developmental, or other dysfunctions in GABAergic neurons have been linked to neurological disorders such as epilepsy. Thus, it is crucial to investigate the interaction of these various neurons and to develop methods to specifically and directly monitor inhibitory activity in vivo. While research in small mammals has benefited from a wealth of recent technological development, bridging the gap to large mammals and humans remains a challenge. This is of particular interest since single neuron monitoring with intracranial electrodes in epileptic patients is developing quickly, opening new avenues for understanding the role of different cell types in epilepsy. Here, we review currently available techniques that monitor inhibitory activity in the brain and the respective validations in rodents. Finally, we discuss the future developments of these techniques and how knowledge from animal research can be translated to the study of neuronal circuit dynamics in the human brain.
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7
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Affiliation(s)
- Tingting Zhou
- Department of Brain and Cognitive Science and the McGovern Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael M Halassa
- Department of Brain and Cognitive Science and the McGovern Institute, Massachusetts Institute of Technology, Cambridge, MA, USA.
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8
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Abstract
The thalamocortical pathway is the main route of communication between the eye and the cerebral cortex. During embryonic development, thalamocortical afferents travel to L4 and are sorted by receptive field position, eye of origin, and contrast polarity (i.e., preference for light or dark stimuli). In primates and carnivores, this sorting involves numerous afferents, most of which sample a limited region of the binocular field. Devoting abundant thalamocortical resources to process a limited visual field has a clear advantage: It allows many stimulus combinations to be sampled at each spatial location. Moreover, the sampling efficiency can be further enhanced by organizing the afferents in a cortical grid for eye input and contrast polarity. We argue that thalamocortical interactions within this eye-polarity grid can be used to represent multiple stimulus combinations found in nature and to build an accurate cortical map for multidimensional stimulus space.
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Affiliation(s)
- Jens Kremkow
- Neuroscience Research Center, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany.,Institute for Theoretical Biology, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
| | - Jose-Manuel Alonso
- Department of Biological and Visual Sciences, College of Optometry, State University of New York, New York, NY 10036, USA;
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9
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Abstract
Cortical networks are composed of glutamatergic excitatory projection neurons and local GABAergic inhibitory interneurons that gate signal flow and sculpt network dynamics. Although they represent a minority of the total neocortical neuronal population, GABAergic interneurons are highly heterogeneous, forming functional classes based on their morphological, electrophysiological, and molecular features, as well as connectivity and in vivo patterns of activity. Here we review our current understanding of neocortical interneuron diversity and the properties that distinguish cell types. We then discuss how the involvement of multiple cell types, each with a specific set of cellular properties, plays a crucial role in diversifying and increasing the computational power of a relatively small number of simple circuit motifs forming cortical networks. We illustrate how recent advances in the field have shed light onto the mechanisms by which GABAergic inhibition contributes to network operations.
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Retinal Circuitry Balances Contrast Tuning of Excitation and Inhibition to Enable Reliable Computation of Direction Selectivity. J Neurosci 2017; 36:5861-76. [PMID: 27225774 DOI: 10.1523/jneurosci.4013-15.2016] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 04/23/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Feedforward (FF) inhibition is a common motif in many neural networks. Typically, excitatory inputs drive both principal neurons and interneurons; the interneurons then inhibit the principal neurons, thereby regulating the strength and timing of the FF signal. The interneurons introduce a likely nonlinear processing step that could distort the excitation/inhibition (E/I) ratio in the principal neuron, potentially degrading the reliability of computation in the circuit. In the retina, FF inhibition is an essential feature of the circuitry underlying direction selectivity (DS): glutamatergic bipolar cells (BCs) provide excitatory input to direction-selective ganglion cells (DSGCs) and GABAergic starburst amacrine cells (SACs), and the SACs then provide FF inhibition onto DSGCs. Robust DS computation requires a consistent synaptic E/I ratio in the DSGC in various visual conditions. Here, we show in mouse retina that the E/I ratio is maintained in DSGCs over a wide stimulus contrast range due to compensatory mechanisms in the diverse population of presynaptic BCs. BC inputs to SACs exhibit higher contrast sensitivity, so that the subsequent nonlinear transformation in SACs reduces the contrast sensitivity of FF inhibition to match the sensitivity of direct excitatory inputs onto DSGCs. Measurements of light-evoked responses from individual BC synaptic terminals suggest that the distinct sensitivity of BC inputs reflects different contrast sensitivity between BC subtypes. Numerical simulations suggest that this network arrangement is crucial for reliable DS computation. SIGNIFICANCE STATEMENT Properly balanced excitation and inhibition are essential for many neuronal computations across brain regions. Feedforward inhibition circuitry, in which a common excitatory source drives both the principal cell and an interneuron, is a typical mechanism by which neural networks maintain this balance. Feedforward circuits may become imbalanced at low stimulation levels, however, if the excitatory drive is too weak to overcome the activation threshold in the interneuron. Here we reveal how excitation and inhibition remain balanced in direction selective ganglion cells in the mouse retina over a wide visual stimulus range.
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11
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Intracellular, In Vivo, Dynamics of Thalamocortical Synapses in Visual Cortex. J Neurosci 2017; 37:5250-5262. [PMID: 28438969 DOI: 10.1523/jneurosci.3370-16.2017] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/24/2017] [Accepted: 04/01/2017] [Indexed: 11/21/2022] Open
Abstract
Seminal studies of the thalamocortical circuit in the visual system of the cat have been central to our understanding of sensory encoding. However, thalamocortical synaptic properties remain poorly understood. We used paired recordings, in the lateral geniculate nucleus (LGN) and primary visual cortex (V1), to provide the first in vivo characterization of sensory-driven thalamocortical potentials in V1. The amplitudes of EPSPs we characterized were smaller than those previously reported in vitro Consistent with prior findings, connected LGN-V1 pairs were only found when their receptive fields (RFs) overlapped, and the probability of connection increased steeply with degree of RF overlap and response similarity. However, surprisingly, we found no relationship between EPSP amplitudes and the similarity of RFs or responses, suggesting different connectivity models for intracortical and thalamocortical circuits. Putative excitatory regular-spiking (RS) and inhibitory fast-spiking (FS) V1 cells had similar EPSP characteristics, showing that in the visual system, feedforward excitation and inhibition are driven with equal strength by the thalamus. Similar to observations in the somatosensory cortex, FS V1 cells received less specific input from LGN. Finally, orientation tuning in V1 was not inherited from single presynaptic LGN cells, suggesting that it must emerge exclusively from the combined input of all presynaptic LGN cells. Our results help to decipher early visual encoding circuits and have immediate utility in providing physiological constraints to computational models of the visual system.SIGNIFICANCE STATEMENT To understand how the brain encodes the visual environment, we must understand the transfer of visual signals between various regions of the brain. Therefore, understanding synaptic dynamics is critical to our understanding of sensory encoding. This study provides the first characterization of visually evoked synaptic potentials between the visual thalamus and visual cortex in an intact animal. To record these potentials, we simultaneously recorded the extracellular potential of presynaptic thalamic cells and the intracellular potential of postsynaptic cortical cells in input layers of primary visual cortex. Our characterization of synaptic potentials in vivo disagreed with prior findings in vitro This study will increase our understanding of thalamocortical circuits and will improve computational models of visual encoding.
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12
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Favorov OV, Kursun O, Tommerdahl M. Role of Feed-Forward Inhibition in Neocortical Information Processing: Implications for Neurological Disorders. THE PHYSICS OF THE MIND AND BRAIN DISORDERS 2017. [DOI: 10.1007/978-3-319-29674-6_17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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13
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Transplanted embryonic neurons integrate into adult neocortical circuits. Nature 2016; 539:248-253. [DOI: 10.1038/nature20113] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 09/23/2016] [Indexed: 12/19/2022]
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14
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Ramamurthy DL, Krubitzer LA. The evolution of whisker-mediated somatosensation in mammals: Sensory processing in barrelless S1 cortex of a marsupial, Monodelphis domestica. J Comp Neurol 2016; 524:3587-3613. [PMID: 27098555 DOI: 10.1002/cne.24018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 04/13/2016] [Accepted: 04/13/2016] [Indexed: 11/06/2022]
Abstract
Movable tactile sensors in the form of whiskers are present in most mammals, but sensory coding in the cortical whisker representation has been studied almost exclusively in mice and rats. Many species that possess whiskers lack the modular "barrel" organization found in the primary somatosensory cortex (S1) of mice and rats, but it is unclear how whisker-related input is represented in these species. We used single-unit extracellular recording techniques to characterize receptive fields and response properties in S1 of Monodelphis domestica (short-tailed opossum), a nocturnal, terrestrial marsupial that shared its last common ancestor with placental mammals over 160 million years ago. Short-tailed opossums lack barrels and septa in S1 but show active whisking behavior similar to that of mice and rats. Most neurons in short-tailed opossum S1 exhibited multiwhisker receptive fields, including a single best whisker (BW) and lower magnitude responses to the deflection of surrounding whiskers. Mean tuning width was similar to that reported for mice and rats. Both symmetrical and asymmetrical receptive fields were present. Neurons tuned to ventral whiskers tended to show broad tuning along the rostrocaudal axis. Thus, despite the absence of barrels, most receptive field properties were similar to those reported for mice and rats. However, unlike those species, S1 neuronal responses to BW and surround whisker deflection showed comparable latencies in short-tailed opossums. This dissimilarity suggests that some aspects of barrel cortex function may not generalize to tactile processing across mammalian species and may be related to differences in the architecture of the whisker-to-cortex pathway. J. Comp. Neurol. 524:3587-3613, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Deepa L Ramamurthy
- Center for Neuroscience, University of California, Davis, Davis, California, 95618
| | - Leah A Krubitzer
- Center for Neuroscience, University of California, Davis, Davis, California, 95618.
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15
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Abstract
Low-level perception results from neural-based computations, which build a multimodal skeleton of unconscious or self-generated inferences on our environment. This review identifies bottleneck issues concerning the role of early primary sensory cortical areas, mostly in rodent and higher mammals (cats and non-human primates), where perception substrates can be searched at multiple scales of neural integration. We discuss the limitation of purely bottom-up approaches for providing realistic models of early sensory processing and the need for identification of fast adaptive processes, operating within the time of a percept. Future progresses will depend on the careful use of comparative neuroscience (guiding the choices of experimental models and species adapted to the questions under study), on the definition of agreed-upon benchmarks for sensory stimulation, on the simultaneous acquisition of neural data at multiple spatio-temporal scales, and on the in vivo identification of key generic integration and plasticity algorithms validated experimentally and in simulations.
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16
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Simons DJ, Carvell GE, Kyriazi HT. Alterations in functional thalamocortical connectivity following neonatal whisker trimming with adult regrowth. J Neurophysiol 2015; 114:1912-22. [PMID: 26245317 DOI: 10.1152/jn.00488.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/05/2015] [Indexed: 11/22/2022] Open
Abstract
Neonatal whisker trimming followed by adult whisker regrowth leads to higher responsiveness and altered receptive field properties of cortical neurons in corresponding layer 4 barrels. Studies of functional thalamocortical (TC) connectivity in normally reared adult rats have provided insights into how experience-dependent TC synaptic plasticity could impact the establishment of feedforward excitatory and inhibitory receptive fields. The present study employed cross-correlation analyses to investigate lasting effects of neonatal whisker trimming on functional connections between simultaneously recorded thalamic neurons and regular-spike (RS), presumed excitatory, and fast-spike (FS), presumed inhibitory, barrel neurons. We find that, as reported previously, RS and FS cells in whisker-trimmed animals fire more during the earliest phase of their whisker-evoked responses, corresponding to the arrival of TC inputs, despite a lack of change or even a slight decrease in the firing of thalamic cells that contact them. Functional connections from thalamus to cortex are stronger. The probability of finding TC-RS connections was twofold greater in trimmed animals and similar to the frequency of TC-FS connections in control and trimmed animals, the latter being unaffected by whisker trimming. Unlike control cases, trimmed RS units are more likely to receive inputs from TC units (TCUs) and have mismatched angular tuning and even weakly responsive TCUs make strong functional connections on them. Results indicate that developmentally appropriate tactile experience early in life promotes the differential thalamic engagement of excitatory and inhibitory cortical neurons that underlies normal barrel function.
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Affiliation(s)
- D J Simons
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and
| | - G E Carvell
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - H T Kyriazi
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and
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17
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Volgushev M, Ilin V, Stevenson IH. Identifying and tracking simulated synaptic inputs from neuronal firing: insights from in vitro experiments. PLoS Comput Biol 2015; 11:e1004167. [PMID: 25823000 PMCID: PMC4379067 DOI: 10.1371/journal.pcbi.1004167] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 02/02/2015] [Indexed: 11/18/2022] Open
Abstract
Accurately describing synaptic interactions between neurons and how interactions change over time are key challenges for systems neuroscience. Although intracellular electrophysiology is a powerful tool for studying synaptic integration and plasticity, it is limited by the small number of neurons that can be recorded simultaneously in vitro and by the technical difficulty of intracellular recording in vivo. One way around these difficulties may be to use large-scale extracellular recording of spike trains and apply statistical methods to model and infer functional connections between neurons. These techniques have the potential to reveal large-scale connectivity structure based on the spike timing alone. However, the interpretation of functional connectivity is often approximate, since only a small fraction of presynaptic inputs are typically observed. Here we use in vitro current injection in layer 2/3 pyramidal neurons to validate methods for inferring functional connectivity in a setting where input to the neuron is controlled. In experiments with partially-defined input, we inject a single simulated input with known amplitude on a background of fluctuating noise. In a fully-defined input paradigm, we then control the synaptic weights and timing of many simulated presynaptic neurons. By analyzing the firing of neurons in response to these artificial inputs, we ask 1) How does functional connectivity inferred from spikes relate to simulated synaptic input? and 2) What are the limitations of connectivity inference? We find that individual current-based synaptic inputs are detectable over a broad range of amplitudes and conditions. Detectability depends on input amplitude and output firing rate, and excitatory inputs are detected more readily than inhibitory. Moreover, as we model increasing numbers of presynaptic inputs, we are able to estimate connection strengths more accurately and detect the presence of connections more quickly. These results illustrate the possibilities and outline the limits of inferring synaptic input from spikes.
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Affiliation(s)
- Maxim Volgushev
- Department of Psychology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Vladimir Ilin
- Department of Psychology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Ian H. Stevenson
- Department of Psychology, University of Connecticut, Storrs, Connecticut, United States of America
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18
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Target-specific properties of thalamocortical synapses onto layer 4 of mouse primary visual cortex. J Neurosci 2015; 34:15455-65. [PMID: 25392512 DOI: 10.1523/jneurosci.2595-14.2014] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In primary sensory cortices, thalamocortical (TC) inputs can directly activate excitatory and inhibitory neurons. In vivo experiments in the main input layer (L4) of primary visual cortex (V1) have shown that excitatory and inhibitory neurons have different tuning properties. The different functional properties may arise from distinct intrinsic properties of L4 neurons, but could also depend on cell type-specific properties of the synaptic inputs from the lateral geniculate nucleus of the thalamus (LGN) onto L4 neurons. While anatomical studies identified LGN inputs onto both excitatory and inhibitory neurons in V1, their synaptic properties have not been investigated. Here we used an optogenetic approach to selectively activate LGN terminal fields in acute coronal slices containing V1, and recorded monosynaptic currents from excitatory and inhibitory neurons in L4. LGN afferents made monosynaptic connections with pyramidal (Pyr) and fast-spiking (FS) neurons. TC EPSCs on FS neurons were larger and showed steeper short-term depression in response to repetitive stimulation than those on Pyr neurons. LGN inputs onto Pyr and FS neurons also differed in postsynaptic receptor composition and organization of presynaptic release sites. Together, our results demonstrate that LGN input onto L4 neurons in mouse V1 have target-specific presynaptic and postsynaptic properties. Distinct mechanisms of activation of feedforward excitatory and inhibitory neurons in the main input layer of V1 are likely to endow neurons with different response properties to incoming visual stimuli.
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Carrasco A, Brown TA, Lomber SG. Spectral and Temporal Acoustic Features Modulate Response Irregularities within Primary Auditory Cortex Columns. PLoS One 2014; 9:e114550. [PMID: 25494365 PMCID: PMC4262427 DOI: 10.1371/journal.pone.0114550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 11/05/2014] [Indexed: 11/18/2022] Open
Abstract
Assemblies of vertically connected neurons in the cerebral cortex form information processing units (columns) that participate in the distribution and segregation of sensory signals. Despite well-accepted models of columnar architecture, functional mechanisms of inter-laminar communication remain poorly understood. Hence, the purpose of the present investigation was to examine the effects of sensory information features on columnar response properties. Using acute recording techniques, extracellular response activity was collected from the right hemisphere of eight mature cats (felis catus). Recordings were conducted with multichannel electrodes that permitted the simultaneous acquisition of neuronal activity within primary auditory cortex columns. Neuronal responses to simple (pure tones), complex (noise burst and frequency modulated sweeps), and ecologically relevant (con-specific vocalizations) acoustic signals were measured. Collectively, the present investigation demonstrates that despite consistencies in neuronal tuning (characteristic frequency), irregularities in discharge activity between neurons of individual A1 columns increase as a function of spectral (signal complexity) and temporal (duration) acoustic variations.
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Affiliation(s)
- Andres Carrasco
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada
- Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Trecia A. Brown
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada
- Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Stephen G. Lomber
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada
- Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
- Department of Psychology, University of Western Ontario, London, Ontario, Canada
- National Centre for Audiology, University of Western Ontario, London, Ontario, Canada
- * E-mail:
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20
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Bauer R, Zubler F, Pfister S, Hauri A, Pfeiffer M, Muir DR, Douglas RJ. Developmental self-construction and -configuration of functional neocortical neuronal networks. PLoS Comput Biol 2014; 10:e1003994. [PMID: 25474693 PMCID: PMC4256067 DOI: 10.1371/journal.pcbi.1003994] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 10/09/2014] [Indexed: 11/20/2022] Open
Abstract
The prenatal development of neural circuits must provide sufficient configuration to support at least a set of core postnatal behaviors. Although knowledge of various genetic and cellular aspects of development is accumulating rapidly, there is less systematic understanding of how these various processes play together in order to construct such functional networks. Here we make some steps toward such understanding by demonstrating through detailed simulations how a competitive co-operative (‘winner-take-all’, WTA) network architecture can arise by development from a single precursor cell. This precursor is granted a simplified gene regulatory network that directs cell mitosis, differentiation, migration, neurite outgrowth and synaptogenesis. Once initial axonal connection patterns are established, their synaptic weights undergo homeostatic unsupervised learning that is shaped by wave-like input patterns. We demonstrate how this autonomous genetically directed developmental sequence can give rise to self-calibrated WTA networks, and compare our simulation results with biological data. Models of learning in artificial neural networks generally assume that the neurons and approximate network are given, and then learning tunes the synaptic weights. By contrast, we address the question of how an entire functional neuronal network containing many differentiated neurons and connections can develop from only a single progenitor cell. We chose a winner-take-all network as the developmental target, because it is a computationally powerful circuit, and a candidate motif of neocortical networks. The key aspect of this challenge is that the developmental mechanisms must be locally autonomous as in Biology: They cannot depend on global knowledge or supervision. We have explored this developmental process by simulating in physical detail the fundamental biological behaviors, such as cell proliferation, neurite growth and synapse formation that give rise to the structural connectivity observed in the superficial layers of the neocortex. These differentiated, approximately connected neurons then adapt their synaptic weights homeostatically to obtain a uniform electrical signaling activity before going on to organize themselves according to the fundamental correlations embedded in a noisy wave-like input signal. In this way the precursor expands itself through development and unsupervised learning into winner-take-all functionality and orientation selectivity in a biologically plausible manner.
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Affiliation(s)
- Roman Bauer
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
- School of Computing Science, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail:
| | - Frédéric Zubler
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
- Department of Neurology, Inselspital Bern, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Sabina Pfister
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
| | - Andreas Hauri
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
| | - Michael Pfeiffer
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
| | - Dylan R. Muir
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
- Biozentrum, University of Basel, Basel, Switzerland
| | - Rodney J. Douglas
- Institute of Neuroinformatics, University/ETH Zürich, Zürich, Switzerland
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21
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Chan KC, Fan SJ, Chan RW, Cheng JS, Zhou IY, Wu EX. In vivo visuotopic brain mapping with manganese-enhanced MRI and resting-state functional connectivity MRI. Neuroimage 2014; 90:235-45. [PMID: 24394694 PMCID: PMC3951771 DOI: 10.1016/j.neuroimage.2013.12.056] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 12/16/2013] [Accepted: 12/23/2013] [Indexed: 12/16/2022] Open
Abstract
The rodents are an increasingly important model for understanding the mechanisms of development, plasticity, functional specialization and disease in the visual system. However, limited tools have been available for assessing the structural and functional connectivity of the visual brain network globally, in vivo and longitudinally. There are also ongoing debates on whether functional brain connectivity directly reflects structural brain connectivity. In this study, we explored the feasibility of manganese-enhanced MRI (MEMRI) via 3 different routes of Mn(2+) administration for visuotopic brain mapping and understanding of physiological transport in normal and visually deprived adult rats. In addition, resting-state functional connectivity MRI (RSfcMRI) was performed to evaluate the intrinsic functional network and structural-functional relationships in the corresponding anatomical visual brain connections traced by MEMRI. Upon intravitreal, subcortical, and intracortical Mn(2+) injection, different topographic and layer-specific Mn enhancement patterns could be revealed in the visual cortex and subcortical visual nuclei along retinal, callosal, cortico-subcortical, transsynaptic and intracortical horizontal connections. Loss of visual input upon monocular enucleation to adult rats appeared to reduce interhemispheric polysynaptic Mn(2+) transfer but not intra- or inter-hemispheric monosynaptic Mn(2+) transport after Mn(2+) injection into visual cortex. In normal adults, both structural and functional connectivity by MEMRI and RSfcMRI was stronger interhemispherically between bilateral primary/secondary visual cortex (V1/V2) transition zones (TZ) than between V1/V2 TZ and other cortical nuclei. Intrahemispherically, structural and functional connectivity was stronger between visual cortex and subcortical visual nuclei than between visual cortex and other subcortical nuclei. The current results demonstrated the sensitivity of MEMRI and RSfcMRI for assessing the neuroarchitecture, neurophysiology and structural-functional relationships of the visual brains in vivo. These may possess great potentials for effective monitoring and understanding of the basic anatomical and functional connections in the visual system during development, plasticity, disease, pharmacological interventions and genetic modifications in future studies.
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Affiliation(s)
- Kevin C Chan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; UPMC Eye Center, Ophthalmology and Visual Science Research Center, Louis J. Fox Center for Vision Restoration, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Shu-Juan Fan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Russell W Chan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Joe S Cheng
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Iris Y Zhou
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Anatomy, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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22
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Silbereis JC, Nobuta H, Tsai HH, Heine VM, McKinsey GL, Meijer DH, Howard MA, Petryniak MA, Potter GB, Alberta JA, Baraban SC, Stiles CD, Rubenstein JLR, Rowitch DH. Olig1 function is required to repress dlx1/2 and interneuron production in Mammalian brain. Neuron 2014; 81:574-87. [PMID: 24507192 DOI: 10.1016/j.neuron.2013.11.024] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2013] [Indexed: 12/21/2022]
Abstract
Abnormal GABAergic interneuron density, and imbalance of excitatory versus inhibitory tone, is thought to result in epilepsy, neurodevelopmental disorders, and psychiatric disease. Recent studies indicate that interneuron cortical density is determined primarily by the size of the precursor pool in the embryonic telencephalon. However, factors essential for regulating interneuron allocation from telencephalic multipotent precursors are poorly understood. Here we report that Olig1 represses production of GABAergic interneurons throughout the mouse brain. Olig1 deletion in mutant mice results in ectopic expression and upregulation of Dlx1/2 genes in the ventral medial ganglionic eminences and adjacent regions of the septum, resulting in an ∼30% increase in adult cortical interneuron numbers. We show that Olig1 directly represses the Dlx1/2 I12b intergenic enhancer and that Dlx1/2 functions genetically downstream of Olig1. These findings establish Olig1 as an essential repressor of Dlx1/2 and interneuron production in developing mammalian brain.
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Affiliation(s)
- John C Silbereis
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA; Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Hiroko Nobuta
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Hui-Hsin Tsai
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Vivi M Heine
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Gabriel L McKinsey
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Dimphna H Meijer
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - Mackenzie A Howard
- Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Magda A Petryniak
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Gregory B Potter
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - John A Alberta
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - Scott C Baraban
- Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Charles D Stiles
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - John L R Rubenstein
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94143, USA
| | - David H Rowitch
- Department of Pediatrics, Eli and Edythe Broad Institute for Stem Cell Research and Regeneration Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Neurosurgery, University of California, San Francisco, San Francisco, CA 94143, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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23
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Layer 4 in primary visual cortex of the awake rabbit: contrasting properties of simple cells and putative feedforward inhibitory interneurons. J Neurosci 2013; 33:11372-89. [PMID: 23843510 DOI: 10.1523/jneurosci.0863-13.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Extracellular recordings were obtained from two cell classes in layer 4 of the awake rabbit primary visual cortex (V1): putative inhibitory interneurons [suspected inhibitory interneurons (SINs)] and putative excitatory cells with simple receptive fields. SINs were identified solely by their characteristic response to electrical stimulation of the lateral geniculate nucleus (LGN, 3+ spikes at >600 Hz), and simple cells were identified solely by receptive field structure, requiring spatially separate ON and/or OFF subfields. Notably, no cells met both criteria, and we studied 62 simple cells and 33 SINs. Fourteen cells met neither criterion. These layer 4 populations were markedly distinct. Thus, SINs were far less linear (F1/F0 < 1), more broadly tuned to stimulus orientation, direction, spatial and temporal frequency, more sensitive to contrast, had much higher spontaneous and stimulus-driven activity, and always had spatially overlapping ON/OFF receptive subfields. SINs responded to drifting gratings with increased firing rates (F0) for all orientations and directions. However, some SINs showed a weaker modulated (F1) response sharply tuned to orientation and/or direction. SINs responded at shorter latencies than simple cells to stationary stimuli, and the responses of both populations could be sustained or transient. Transient simple cells were more sensitive to contrast than sustained simple cells and their visual responses were more frequently suppressed by high contrasts. Finally, cross-correlation between LGN and SIN spike trains confirmed a fast and precisely timed monosynaptic connectivity, supporting the notion that SINs are well suited to provide a fast feedforward inhibition onto targeted cortical populations.
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24
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Kwegyir-Afful EE, Kyriazi HT, Simons DJ. Weaker feedforward inhibition accounts for less pronounced thalamocortical response transformation in mouse vs. rat barrels. J Neurophysiol 2013; 110:2378-92. [PMID: 23966677 DOI: 10.1152/jn.00574.2012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Feedforward inhibition is a common motif of thalamocortical circuits. Strong engagement of inhibitory neurons by thalamic inputs enhances response differentials between preferred and nonpreferred stimuli. In rat whisker-barrel cortex, robustly driven inhibitory barrel neurons establish a brief epoch during which synchronous or near-synchronous thalamic firing produces larger responses to preferred stimuli, such as high-velocity deflections of the principal whisker in a preferred direction. Present experiments in mice show that barrel neuron responses to preferred vs. nonpreferred stimuli differ less than in rats. In addition, fast-spike units, thought to be inhibitory barrel neurons, fire less robustly to whisker stimuli in mice than in rats. Analyses of real and simulated data indicate that mouse barrel circuitry integrates thalamic inputs over a broad temporal window, and that, as a consequence, responses of barrel neurons are largely similar to those of thalamic neurons. Results are consistent with weaker feedforward inhibition in mouse barrels. Differences in thalamocortical circuitry between mice and rats may reflect mechanical properties of the whiskers themselves.
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Affiliation(s)
- E E Kwegyir-Afful
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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25
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Abstract
Knowledge of thalamocortical (TC) processing comes mainly from studying core thalamic systems that project to middle layers of primary sensory cortices. However, most thalamic relay neurons comprise a matrix of cells that are densest in the "nonspecific" thalamic nuclei and usually target layer 1 (L1) of multiple cortical areas. A longstanding hypothesis is that matrix TC systems are crucial for regulating neocortical excitability during changing behavioral states, yet we know almost nothing about the mechanisms of such regulation. It is also unclear whether synaptic and circuit mechanisms that are well established for core sensory TC systems apply to matrix TC systems. Here we describe studies of thalamic matrix influences on mouse prefrontal cortex using optogenetic and in vitro electrophysiology techniques. Channelrhodopsin-2 was expressed in midline and paralaminar (matrix) thalamic neurons, and their L1-projecting TC axons were activated optically. Contrary to conventional views, we found that matrix TC projections to L1 could transmit relatively strong, fast, high-fidelity synaptic signals. L1 TC projections preferentially drove inhibitory interneurons of L1, especially those of the late-spiking subtype, and often triggered feedforward inhibition in both L1 interneurons and pyramidal cells of L2/L3. Responses during repetitive stimulation were far more sustained for matrix than for core sensory TC pathways. Thus, matrix TC circuits appear to be specialized for robust transmission over relatively extended periods, consistent with the sort of persistent activation observed during working memory and potentially applicable to state-dependent regulation of excitability.
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26
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Abstract
During behavioral quiescence, the neocortex generates spontaneous slow oscillations, which may consist of up-states and down-states. Up-states are short epochs of persistent activity that resemble the activated neocortex during arousal and cognition. Neural activity in neocortical pathways can trigger up-states, but the variables that control their occurrence are poorly understood. We used thalamocortical slices from adult mice to explore the role of thalamocortical and intracortical synaptic cooperativity (the number of coincident afferents) in driving up-states. Cooperativity was adjusted by varying the intensity of electrical or blue-light stimuli in pathways that express channelrhodopsin-2. We found that optogenetics greatly improves the study of thalamocortical pathways in slices because it produces thalamocortical responses that resemble those observed in vivo. The results indicate that more synaptic cooperativity, caused by either thalamocortical or intracortical fast AMPA-receptor excitation, leads to more robust inhibition of up-states because it drives stronger feedforward inhibition. Conversely, during strong synaptic cooperativity that suppresses up-states, blocking fast excitation, and as a result the feedforward inhibition it drives, unmasks up-states entirely mediated by slow NMDA-receptor excitation. Regardless of the pathway's origin, cooperativity mediated by fast excitation is inversely related to the ability of excitatory synaptic pathways to trigger up-states in neocortex.
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27
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Abstract
"Receptive Fields, Binocular Interaction and Functional Architecture in the Cat's Visual Cortex" by Hubel and Wiesel (1962) reported several important discoveries: orientation columns, the distinct structures of simple and complex receptive fields, and binocular integration. But perhaps the paper's greatest influence came from the concept of functional architecture (the complex relationship between in vivo physiology and the spatial arrangement of neurons) and several models of functionally specific connectivity. They thus identified two distinct concepts, topographic specificity and functional specificity, which together with cell-type specificity constitute the major determinants of nonrandom cortical connectivity. Orientation columns are iconic examples of topographic specificity, whereby axons within a column connect with cells of a single orientation preference. Hubel and Wiesel also saw the need for functional specificity at a finer scale in their model of thalamic inputs to simple cells, verified in the 1990s. The difficult but potentially more important question of functional specificity between cortical neurons is only now becoming tractable with new experimental techniques.
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Affiliation(s)
- R Clay Reid
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02138, USA.
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28
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Abstract
OBJECTIVE To investigate the clinical correlates of central nervous system alterations among women with vulvodynia. Altered central sensitization has been linked to dysfunction in central nervous system-inhibitory pathways (e.g., γ-aminobutyric acidergic), and metrics of sensory adaptation, a centrally mediated process that is sensitive to this dysfunction, could potentially be used to identify women at risk of treatment failure using conventional approaches. METHODS Twelve women with vulvodynia and 20 age-matched controls participated in this study, which was conducted by sensory testing of the right hand's index and middle fingers. The following sensory precepts were assessed: (1) vibrotactile detection threshold; (2) amplitude discrimination capacity (defined as the ability to detect differences in intensity of simultaneously delivered stimuli to 2 fingers); and (3) a metric of adaptation (determined by the impact that applying conditioning stimuli have on amplitude discriminative capacity). RESULTS Participants did not differ on key demographic variables, vibrotactile detection threshold, and amplitude discrimination capacity. However, we found significant differences from controls in adaptation metrics in 1 subgroup of vulvodynia patients. Compared with healthy controls and women with a shorter history of pain [n=5; duration (y) = 3.4 ± 1.3], those with a longer history [n=7; duration (y) = 9.3 ± 1.4)] were found to be less likely to have adaptation metrics similar to control values. DISCUSSION Chronic pain is thought to lead to altered central sensitization, and adaptation is a centrally mediated process that is sensitive to this condition. This report suggests that similar alterations exist in a subgroup of vulvodynia patients.
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29
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Pita-Almenar JD, Ranganathan GN, Koester HJ. Impact of cortical plasticity on patterns of suprathreshold activity in the cerebral cortex. J Neurophysiol 2011; 107:850-8. [PMID: 22072515 DOI: 10.1152/jn.00245.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There are many cellular and synaptic mechanisms of plasticity in the vertebrate cortex. How the patterns of suprathreshold spiking activity in a population of neurons change because of this plasticity, however, has hardly been subjected to experimental studies. Here, we measured how evoked patterns of suprathreshold spiking activity in a cortical network were modified by cortical plasticity with single-cell and single-spike resolution. To record patterns of activity in the rodent barrel cortex, we used optical methods to detect suprathreshold activity from up to 40 neurons simultaneously. Pairing of two inputs resulted in a long-lasting modification of the cortical responses evoked by one of the inputs. The results indicate that plasticity rules on the network level inherit properties from synaptic plasticity rules but are also determined by the functional synaptic architecture, as well as the computations carried out in cortical networks. The largest determinants of the modified cortical responses were those observed when inducing changes by pairing the two inputs. On the single-neuron level, the modified responses only weakly reflected those observed when pairing the two inputs for induction of plasticity. Despite the weak reflection on the cellular level, however, the modified patterns reflected the pairing patterns to the degree that a simple decoding mechanism-a linear separator-correctly discriminated the modified responses from other patterns of activity.
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Affiliation(s)
- Juan Diego Pita-Almenar
- Center for Learning and Memory, Section of Neurobiology, The Univ. of Texas at Austin, Austin, TX 78712, USA
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30
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Fast-spiking interneurons have an initial orientation bias that is lost with vision. Nat Neurosci 2011; 14:1121-3. [PMID: 21750548 PMCID: PMC3164933 DOI: 10.1038/nn.2890] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 07/05/2011] [Indexed: 12/13/2022]
Abstract
We found that in mice, following eye opening, fast-spiking, parvalbumin-positive GABAergic interneurons had well-defined orientation tuning preferences and that subsequent visual experience broadened this tuning. Broad inhibitory tuning was not required for the developmental sharpening of excitatory tuning but did precede binocular matching of excitatory orientation tuning. We propose that experience-dependent broadening of inhibition is a candidate for initiating the critical period of excitatory binocular plasticity in developing visual cortex.
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31
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Bruno RM. Synchrony in sensation. Curr Opin Neurobiol 2011; 21:701-8. [PMID: 21723114 DOI: 10.1016/j.conb.2011.06.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 06/06/2011] [Accepted: 06/07/2011] [Indexed: 11/25/2022]
Abstract
How neurons encode information has been a hotly debated issue. Ultimately, any code must be relevant to the senders, receivers, and connections between them. This review focuses on the transmission of sensory information through the circuit linking thalamus and cortex, two distant brain regions. Strong feedforward inhibition in the thalamocortical circuit renders cortex highly sensitive to the thalamic synchrony evoked by a sensory stimulus. Neuromodulators and feedback connections may modulate the temporal sensitivity of such circuits and gate the propagation of synchrony into other layers and cortical areas. The prevalence of strong feedforward inhibitory circuits throughout the central nervous system suggests that synchrony codes and timing-sensitive circuits may be widespread, occurring well beyond sensory thalamus and cortex.
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Affiliation(s)
- Randy M Bruno
- Department of Neuroscience and the Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA.
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32
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Abstract
A characteristic feature of the somatosensory cortex in rodents is the presence of discrete cellular aggregates in layer 4 (barrels) that process input from the mystacial vibrissae. Just like thalamic cells that relay vibrissal information to the barrels, barrel cells display directional preference to whisker motion. The present study examined whether the projection of single thalamic cells into a barrel is consistent with the existence of an orderly map of direction preference. The direction preference of single thalamic cells was assessed, and axonal projections were visualized after juxtacellular labeling with biotinylated dextran. Results show that the terminal field of individual thalamic neurons in a barrel is markedly anisotropic and that the location of boutons with respect to the somatotopic map is either positively or negatively correlated with the angular tuning of the thalamic neuron. These results indicate that angular tuning is not represented across a systematic map with fixed anteroposterior/mediolateral coordinates in a barrel. The actual significance of the direction-dependent segregation of thalamocortical terminals in barrels may only come to light in the context of active sensing.
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33
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Favorov OV, Kursun O. Neocortical layer 4 as a pluripotent function linearizer. J Neurophysiol 2011; 105:1342-60. [PMID: 21248059 DOI: 10.1152/jn.00708.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A highly effective kernel-based strategy used in machine learning is to transform the input space into a new "feature" space where nonlinear problems become linear and more readily solvable with efficient linear techniques. We propose that a similar "problem-linearization" strategy is used by the neocortical input layer 4 to reduce the difficulty of learning nonlinear relations between the afferent inputs to a cortical column and its to-be-learned upper layer outputs. The key to this strategy is the presence of broadly tuned feed-forward inhibition in layer 4: it turns local layer 4 domains into functional analogs of radial basis function networks, which are known for their universal function approximation capabilities. With the use of a computational model of layer 4 with feed-forward inhibition and Hebbian afferent connections, self-organized on natural images to closely match structural and functional properties of layer 4 of the cat primary visual cortex, we show that such layer-4-like networks have a strong intrinsic tendency to perform input transforms that automatically linearize a broad repertoire of potential nonlinear functions over the afferent inputs. This capacity for pluripotent function linearization, which is highly robust to variations in network parameters, suggests that layer 4 might contribute importantly to sensory information processing as a pluripotent function linearizer, performing such a transform of afferent inputs to a cortical column that makes it possible for neurons in the upper layers of the column to learn and perform their complex functions using primarily linear operations.
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Affiliation(s)
- Oleg V Favorov
- Department of Biomedical Engineering, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7545, USA.
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34
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Alonso JM. My recollections of Hubel and Wiesel and a brief review of functional circuitry in the visual pathway. J Physiol 2009; 587:2783-90. [PMID: 19525563 DOI: 10.1113/jphysiol.2009.169813] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The first paper of Hubel and Wiesel in The Journal of Physiology in 1959 marked the beginning of an exciting chapter in the history of visual neuroscience. Through a collaboration that lasted 25 years, Hubel and Wiesel described the main response properties of visual cortical neurons, the functional architecture of visual cortex and the role of visual experience in shaping cortical architecture. The work of Hubel and Wiesel transformed the field not only through scientific discovery but also by touching the life and scientific careers of many students. Here, I describe my personal experience as a postdoctoral student with Torsten Wiesel and how this experience influenced my own work.
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Affiliation(s)
- Jose-Manuel Alonso
- Department of Biological Sciences, State University of New York, State College of Optometry, 33 West 42nd Street, New York, NY 10036, USA.
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35
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Abstract
In the mammalian brain, glutamate and gamma-aminobutyric acid are considered major excitatory and inhibitory neurotransmitters, respectively. However, we have found evidence that glutamate can also act as a postsynaptic inhibitory neurotransmitter in layer 4 of the neocortex. Using whole-cell recordings from layer 4 neurons in slice preparations from the mouse visual, auditory, and somatosensory cortices, we found that metabotropic glutamate receptor (mGluR) agonists (ACPD, APDC, and DCG IV) elicit a robust, long-lasting hyperpolarization that is abolished by the group II mGluR antagonist, MCCG. This response largely involves a K(+) conductance mediated by G-protein activity and GIRK channels. Furthermore, electrical and photostimulation of the intracortical inputs to layer 4 elicits a similar hyperpolarization that is blocked by group II mGluR antagonists. This novel inhibition mediated by group II mGluRs may be an unappreciated mechanism for refining cortical receptive fields in layer 4 and may enable synaptic gain control during periods of high activity.
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Affiliation(s)
- Charles C Lee
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA.
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36
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Manipulating critical period closure across different sectors of the primary auditory cortex. Nat Neurosci 2008; 11:957-65. [PMID: 18604205 DOI: 10.1038/nn.2144] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Accepted: 05/22/2008] [Indexed: 11/09/2022]
Abstract
During early brain development and through 'adult' experience-dependent plasticity, neural circuits are shaped to represent the external world with high fidelity. When raised in a quiet environment, the rat primary auditory cortex (A1) has a well-defined 'critical period', lasting several days, for its representation of sound frequency. The addition of environmental noise extends the critical period duration as a variable function of noise level. It remains unclear whether critical period closure should be regarded as a unified, externally gated event that applies for all of A1 or if it is controlled by progressive, local, activity-driven changes in this cortical area. We found that rearing rats in the presence of a spectrally limited noise band resulted in the closure of the critical period for A1 sectors representing the noise-free spectral bands, whereas the critical period appeared to remain open in noise-exposed sectors, where the cortex was still functionally and physically immature.
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37
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Hirata A, Castro-Alamancos MA. Cortical transformation of wide-field (multiwhisker) sensory responses. J Neurophysiol 2008; 100:358-70. [PMID: 18480364 DOI: 10.1152/jn.90538.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the barrel cortex of rodents, cells respond to a principal whisker (PW) and more weakly to several adjacent whiskers (AWs). Here we show that compared with PW responses, simultaneous wide-field stimulation of the PW and several AWs enhances short-latency responses and suppresses long-latency responses. Multiwhisker enhancement and suppression is first seen at the level of the cortex in layer 4 and not in the ventroposterior medial thalamus. Within the cortex, enhancement is manifested as a reduction in spike latency in layer 4 but also as an increase in spike probability in layer 2/3. Intracellular recordings revealed that multiwhisker enhancement of short-latency responses is caused by synaptic summation that can be explained by synaptic cooperativity (i.e., convergence of synaptic inputs activated by different whiskers). Conversely, multiwhisker suppression of long-latency responses is due to increased recruitment of inhibition in cortical cells. Interestingly, the ability to differentiate multiwhisker and PW responses is lost during rapid sensory adaptation caused by high-frequency whisker stimulation. The results reveal that simultaneous and temporally dispersed wide-field sensory inputs are discriminated at the level of single cells in barrel cortex with high temporal resolution, but the ability to compute this difference is highly dynamic and dependent on the level of adaptation in the thalamocortical network.
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Affiliation(s)
- Akio Hirata
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA
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38
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Sun QQ. The missing piece in the 'use it or lose it' puzzle: is inhibition regulated by activity or does it act on its own accord? Rev Neurosci 2007; 18:295-310. [PMID: 18019611 DOI: 10.1515/revneuro.2007.18.3-4.295] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We have gained enormous insight into the mechanisms underlying both activity-dependent and (to a lesser degree) -independent plasticity of excitatory synapses. Recently, cortical inhibition has been shown to play a vital role in the formation of critical periods for sensory plasticity. As such, sculpting of neuronal circuits by inhibition may be a common mechanism by which activity organizes or reorganizes brain circuits. Disturbances in the balance of excitation and inhibition in the neocortex provoke abnormal activities, such as epileptic seizures and abnormal cortical development. However, both the process of experience-dependent postnatal maturation of neocortical inhibitory networks and its underlying mechanisms remain elusive. Mechanisms that match excitation and inhibition are central to achieving balanced function at the level of individual circuits. The goal of this review is to reinforce our understanding of the mechanisms by which developing inhibitory networks are able to adapt to sensory inputs, and to maintain their balance with developing excitatory networks. Discussion is centered on the following questions related to experience-dependent plasticity of neocortical inhibitory networks: 1) What are the roles of GABAergic inhibition in the postnatal maturation of neocortical circuits? 2) Does the maturation of neocortical inhibitory circuits proceed in an activity-dependent manner or do they develop independently of sensory inputs? 3) Does activity regulate inhibitory networks in the same way it regulates excitatory networks? 4) What are the molecular and cellular mechanisms that underlie the activity-dependent maturation of inhibitory networks? 5) What are the functional advantages of experience-dependent plasticity of inhibitory networks to network processing in sensory cortices?
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Affiliation(s)
- Qian-Quan Sun
- Laboratory of Neural Development and Learning, Department of Zoology and Physiology and Neuroscience Program, University of Wyoming, Laramie, WY, USA.
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39
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Liu BH, Wu GK, Arbuckle R, Tao HW, Zhang LI. Defining cortical frequency tuning with recurrent excitatory circuitry. Nat Neurosci 2007; 10:1594-600. [PMID: 17994013 DOI: 10.1038/nn2012] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Accepted: 10/16/2007] [Indexed: 11/09/2022]
Abstract
Neurons in the recipient layers of sensory cortices receive excitatory input from two major sources: the feedforward thalamocortical and recurrent intracortical inputs. To address their respective functional roles, we developed a new method for silencing cortex by competitively activating GABA(A) while blocking GABA(B) receptors. In the rat primary auditory cortex, in vivo whole-cell recording from the same neuron before and after local cortical silencing revealed that thalamic input occupied the same area of frequency-intensity tonal receptive field as the total excitatory input, but showed a flattened tuning curve. In contrast, excitatory intracortical input was sharply tuned with a tuning curve that closely matched that of suprathreshold responses. This can be attributed to a selective amplification of cortical cells' responses at preferred frequencies by intracortical inputs from similarly tuned neurons. Thus, weakly tuned thalamocortical inputs determine the subthreshold responding range, whereas intracortical inputs largely define the tuning. Such circuits may ensure a faithful conveyance of sensory information.
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Affiliation(s)
- Bao-hua Liu
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, USA
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40
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Cardin JA, Palmer LA, Contreras D. Stimulus feature selectivity in excitatory and inhibitory neurons in primary visual cortex. J Neurosci 2007; 27:10333-44. [PMID: 17898205 PMCID: PMC3025280 DOI: 10.1523/jneurosci.1692-07.2007] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although several lines of evidence suggest that stimulus selectivity in somatosensory and visual cortices is critically dependent on unselective inhibition, particularly in the thalamorecipient layer 4, no comprehensive comparison of the responses of excitatory and inhibitory cells has been conducted. Here, we recorded intracellularly from a large population of regular spiking (RS; presumed excitatory) and fast spiking (FS; presumed inhibitory) cells in layers 2-6 of primary visual cortex. In layer 4, where selectivity for orientation and spatial frequency first emerges, we found no untuned FS cells. Instead, the tuning of the spike output of layer 4 FS cells was significantly but moderately broader than that of RS cells. However, the tuning of the underlying synaptic responses was not different, indicating that the difference in spike-output selectivity resulted from differences in the transformation of synaptic input into firing rate. Layer 4 FS cells exhibited significantly lower input resistance and faster time constants than layer 4 RS cells, leading to larger and faster membrane potential (V(m)) fluctuations. FS cell V(m) fluctuations were more broadly tuned than those of RS cells and matched spike-output tuning, suggesting that the broader spike tuning of these cells was driven by visually evoked synaptic noise. These differences were not observed outside of layer 4. Thus, cell type-specific differences in stimulus feature selectivity at the first level of cortical sensory processing may arise as a result of distinct biophysical properties that determine the dynamics of synaptic integration.
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Affiliation(s)
- Jessica A. Cardin
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19106
| | - Larry A. Palmer
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19106
| | - Diego Contreras
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19106
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41
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Haggard P, Christakou A, Serino A. Viewing the body modulates tactile receptive fields. Exp Brain Res 2007; 180:187-93. [PMID: 17508208 DOI: 10.1007/s00221-007-0971-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 04/17/2007] [Indexed: 10/23/2022]
Abstract
Tactile discrimination performance depends on the receptive field (RF) size of somatosensory cortical (SI) neurons. Psychophysical masking effects can reveal the RF of an idealized "virtual" somatosensory neuron. Previous studies show that top-down factors strongly affect tactile discrimination performance. Here, we show that non-informative vision of the touched body part influences tactile discrimination by modulating tactile RFs. Ten subjects performed spatial discrimination between touch locations on the forearm. Performance was improved when subjects saw their forearm compared to viewing a neutral object in the same location. The extent of visual information was relevant, since restricted view of the forearm did not have this enhancing effect. Vibrotactile maskers were placed symmetrically on either side of the tactile target locations, at two different distances. Overall, masking significantly impaired discrimination performance, but the spatial gradient of masking depended on what subjects viewed. Viewing the body reduced the effect of distant maskers, but enhanced the effect of close maskers, as compared to viewing a neutral object. We propose that viewing the body improves functional touch by sharpening tactile RFs in an early somatosensory map. Top-down modulation of lateral inhibition could underlie these effects.
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Affiliation(s)
- Patrick Haggard
- Institute of Cognitive Neuroscience and Department of Psychology, University College London, Alexandra House, 17 Queen Square, London WC1N 3AR, UK.
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42
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Lee SH, Land PW, Simons DJ. Layer- and cell-type-specific effects of neonatal whisker-trimming in adult rat barrel cortex. J Neurophysiol 2007; 97:4380-5. [PMID: 17392411 DOI: 10.1152/jn.01217.2006] [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] [Indexed: 11/22/2022] Open
Abstract
Tactile deprivation in rats produced by whisker-trimming early in life leads to abnormally robust responses of excitatory neurons in layer 4 of primary somatosensory cortex when the re-grown whiskers are stimulated. Present findings from fast-spike neurons indicate that presumed inhibitory cells fire less robustly under the same conditions. These contrasting effects may reflect altered patterns of thalamocortical input to excitatory versus inhibitory cells and/or changes in the strength of intracortical connections. Despite increased excitability of layer 4, neurons in layer 2/3 respond at control levels even after full whisker re-growth. Layer 4 synapses onto supragranular neurons may be permanently depressed as a result of neonatal sensory deprivation.
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Affiliation(s)
- Soo-Hyun Lee
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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43
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Rennaker RL, Chen CFF, Ruyle AM, Sloan AM, Wilson DA. Spatial and temporal distribution of odorant-evoked activity in the piriform cortex. J Neurosci 2007; 27:1534-42. [PMID: 17301162 PMCID: PMC2291208 DOI: 10.1523/jneurosci.4072-06.2007] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Despite a remarkably precise spatial representation of odorant stimuli in the early stages of olfactory processing, the projections to the olfactory (piriform) cortex are more diffuse and show characteristics of a combinatorial array, with extensive overlap of afferent inputs and widespread intracortical association connections. Furthermore, although there is increasing evidence for the importance of temporal structure in olfactory bulb odorant-evoked output, little is known about how this temporal patterning is translated within cortical neural ensembles. The present study used multichannel electrode arrays and paired single-unit recordings in rat anterior piriform cortex to test several predictions regarding ensemble coding in this system. The results indicate that odorants evoke activity in a spatially scattered ensemble of anterior piriform cortex neurons, and the ensemble activity includes a rich temporal structure. The most pronounced discrimination between different odorants by cortical ensembles occurs during the first inhalation of a 2 s stimulus. The distributed spatial and temporal structure of cortical activity is present at both global and local scales, with neighboring single units contributing to coding of different odorants and active at different phases of the respiratory cycle. Finally, cross-correlogram analyses suggest that cortical unit activity reflects not only afferent input from the olfactory bulb but also intrinsic activity within the intracortical association fiber system. These results provide direct evidence for predictions stemming from anatomical- and theoretical-based models of piriform cortex.
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Affiliation(s)
| | - Chien-Fu F. Chen
- Department of Zoology, University of Oklahoma, Norman, Oklahoma 73019
| | | | | | - Donald A. Wilson
- Department of Zoology, University of Oklahoma, Norman, Oklahoma 73019
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44
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Cruikshank SJ, Lewis TJ, Connors BW. Synaptic basis for intense thalamocortical activation of feedforward inhibitory cells in neocortex. Nat Neurosci 2007; 10:462-8. [PMID: 17334362 DOI: 10.1038/nn1861] [Citation(s) in RCA: 411] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Accepted: 02/02/2007] [Indexed: 11/09/2022]
Abstract
The thalamus provides fundamental input to the neocortex. This input activates inhibitory interneurons more strongly than excitatory neurons, triggering powerful feedforward inhibition. We studied the mechanisms of this selective neuronal activation using a mouse somatosensory thalamocortical preparation. Notably, the greater responsiveness of inhibitory interneurons was not caused by their distinctive intrinsic properties but was instead produced by synaptic mechanisms. Axons from the thalamus made stronger and more frequent excitatory connections onto inhibitory interneurons than onto excitatory cells. Furthermore, circuit dynamics allowed feedforward inhibition to suppress responses in excitatory cells more effectively than in interneurons. Thalamocortical excitatory currents rose quickly in interneurons, allowing them to fire action potentials before significant feedforward inhibition emerged. In contrast, thalamocortical excitatory currents rose slowly in excitatory cells, overlapping with feedforward inhibitory currents that suppress action potentials. These results demonstrate the importance of selective synaptic targeting and precise timing in the initial stages of neocortical processing.
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Affiliation(s)
- Scott J Cruikshank
- Department of Neuroscience, Division of Biology & Medicine, Box G-LN, Brown University, Providence, Rhode Island 02912, USA
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45
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Abstract
Despite a remarkably precise spatial representation of odorant stimuli in the early stages of olfactory processing, the projections to the olfactory (piriform) cortex are more diffuse and show characteristics of a combinatorial array, with extensive overlap of afferent inputs and widespread intracortical association connections. Furthermore, although there is increasing evidence for the importance of temporal structure in olfactory bulb odorant-evoked output, little is known about how this temporal patterning is translated within cortical neural ensembles. The present study used multichannel electrode arrays and paired single-unit recordings in rat anterior piriform cortex to test several predictions regarding ensemble coding in this system. The results indicate that odorants evoke activity in a spatially scattered ensemble of anterior piriform cortex neurons, and the ensemble activity includes a rich temporal structure. The most pronounced discrimination between different odorants by cortical ensembles occurs during the first inhalation of a 2 s stimulus. The distributed spatial and temporal structure of cortical activity is present at both global and local scales, with neighboring single units contributing to coding of different odorants and active at different phases of the respiratory cycle. Finally, cross-correlogram analyses suggest that cortical unit activity reflects not only afferent input from the olfactory bulb but also intrinsic activity within the intracortical association fiber system. These results provide direct evidence for predictions stemming from anatomical- and theoretical-based models of piriform cortex.
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46
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Jiao Y, Zhang C, Yanagawa Y, Sun QQ. Major effects of sensory experiences on the neocortical inhibitory circuits. J Neurosci 2006; 26:8691-701. [PMID: 16928857 PMCID: PMC6674381 DOI: 10.1523/jneurosci.2478-06.2006] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
During postnatal development, sensory experiences play critical roles in the refinement of cortical connections. However, both the process of postnatal experience-dependent maturation of neocortical inhibitory networks and its underlying mechanisms remain elusive. Here, we examined the differential properties of intracortical inhibitory networks of layer IV in "sensory-spared" and "sensory-deprived" cortices of glutamate acid decarboxylase 67 (GAD67)-green fluorescent protein (GFP) (delta neo) and wild-type mouse. Our results showed that row D whisker trimming (WT) begun at postnatal day 7 (P7), but not after P15, induced a robust reduction of parvalbumin (PV) expression, measured by the PV/GFP ratio and PV cell densities, in the deprived barrels. WT also induced a robust reduction in the number of inhibitory perisomatic varicosities and synaptic GAD65/67 immunoreactivities in spiny neurons of the deprived barrels. Although the GAD65/67 expressions in interneurons were also downregulated in the deprived barrels, the GFP expression remained unchanged. Patch-clamp recording from spiny cells showed a 1.5-fold reduction of intracortical evoked IPSCs (eIPSCs) in deprived versus spared cortices. The reduction in eIPSCs occurred via changes in presynaptic properties and unitary IPSC amplitudes. Miniature IPSCs showed subtle but significant differences between the two experimental conditions. In addition, properties of the IPSCs in deprived barrels resemble those of IPSCs recorded in immature brains (P7). Together, these results suggest that the properties of local intracortical inhibitory networks are modified by sensory experiences. Perisomatic inhibition mediated by PV-positive basket cells is pruned by sensory deprivation.
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Affiliation(s)
- Yuanyuan Jiao
- Department of Zoology and Physiology and
- Neuroscience Program, University of Wyoming, Laramie, Wyoming 82071, and
| | | | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine and Solution-Oriented Research for Science and Technology, Japan Science and Technology Corporation, Maebashi 371-8511, Japan
| | - Qian-Quan Sun
- Department of Zoology and Physiology and
- Neuroscience Program, University of Wyoming, Laramie, Wyoming 82071, and
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47
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Abstract
During postnatal development, sensory experiences play critical roles in the refinement of cortical connections. However, both the process of postnatal experience-dependent maturation of neocortical inhibitory networks and its underlying mechanisms remain elusive. Here, we examined the differential properties of intracortical inhibitory networks of layer IV in "sensory-spared" and "sensory-deprived" cortices of glutamate acid decarboxylase 67 (GAD67)-green fluorescent protein (GFP) (delta neo) and wild-type mouse. Our results showed that row D whisker trimming (WT) begun at postnatal day 7 (P7), but not after P15, induced a robust reduction of parvalbumin (PV) expression, measured by the PV/GFP ratio and PV cell densities, in the deprived barrels. WT also induced a robust reduction in the number of inhibitory perisomatic varicosities and synaptic GAD65/67 immunoreactivities in spiny neurons of the deprived barrels. Although the GAD65/67 expressions in interneurons were also downregulated in the deprived barrels, the GFP expression remained unchanged. Patch-clamp recording from spiny cells showed a 1.5-fold reduction of intracortical evoked IPSCs (eIPSCs) in deprived versus spared cortices. The reduction in eIPSCs occurred via changes in presynaptic properties and unitary IPSC amplitudes. Miniature IPSCs showed subtle but significant differences between the two experimental conditions. In addition, properties of the IPSCs in deprived barrels resemble those of IPSCs recorded in immature brains (P7). Together, these results suggest that the properties of local intracortical inhibitory networks are modified by sensory experiences. Perisomatic inhibition mediated by PV-positive basket cells is pruned by sensory deprivation.
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48
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Kleinfeld D, Ahissar E, Diamond ME. Active sensation: insights from the rodent vibrissa sensorimotor system. Curr Opin Neurobiol 2006; 16:435-44. [PMID: 16837190 DOI: 10.1016/j.conb.2006.06.009] [Citation(s) in RCA: 267] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2006] [Accepted: 06/29/2006] [Indexed: 11/17/2022]
Abstract
Rats sweep their vibrissae through space to locate objects in their immediate environment. In essence, their view of the proximal world is generated through pliable hairs that tap and palpate objects. The texture and shape of those objects must be discerned for the rat to assess the value of the object. Furthermore, the location of those objects must be specified with reference to the position of the rat's head for the rat to plan its movements. Recent in vivo and in vitro electrophysiological measurements provide insight into the algorithms and mechanisms that underlie these behavioral-based computations.
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Affiliation(s)
- David Kleinfeld
- Department of Physics, University of California at San Diego, 9500 Gilman Drive 0374, La Jolla, 92093, USA.
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49
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Affiliation(s)
- Jose-Manuel Alonso
- Department of Biological Sciences, State University of New York College of Optometry, New York, NY 10036, USA.
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50
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Leal-Campanario R, Delgado-García JM, Gruart A. Microstimulation of the somatosensory cortex can substitute for vibrissa stimulation during Pavlovian conditioning. Proc Natl Acad Sci U S A 2006; 103:10052-7. [PMID: 16782811 PMCID: PMC1479767 DOI: 10.1073/pnas.0603584103] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The primary somatosensory cortex (S1) contains a map representation of the body surface. We hypothesized that S1 stimulation can successfully substitute for (or be substituted by) direct stimulation of skin receptors. We prepared rabbits for evoking eyelid conditioned responses (CRs) using a trace "shock-air puff" paradigm. In a first series of experiments, animals received a conditioned stimulus (CS, a train of electrical pulses) in the whisker pad or in the S1 areas for vibrissae or for the hind limb. In the three cases, the CS was followed 250 ms from its end by an air puff presented to the cornea as an unconditioned stimulus (US). Learning curves from the three groups presented similar values, although animals stimulated with a central CS acquired their CRs faster. In a second series of experiments, animals were divided into four groups and were presented either centrally or peripherally with the same CS for six conditioning sessions. Then, the CS was switched from central to peripheral, or vice versa, for 5 additional days. Conditioned animals were not able to discriminate between peripheral (vibrissae) stimuli and stimuli presented to the corresponding S1 (vibrissae) area, but they were able to discriminate between CSs presented to S1 (hind limb) and body (vibrissae) regions. The kinetic properties of evoked CRs were not modified by CS switching. It is proposed that S1 allows the construction of somatosensory percepts of the body surface but does not allow distinguishing the central or peripheral location of the evoking stimuli.
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Affiliation(s)
| | | | - Agnès Gruart
- División de Neurociencias, Universidad Pablo de Olavide, 41013 Sevilla, Spain
- *To whom correspondence should be addressed. E-mail:
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