Adult plasticity in the visual system

1995 ◽  
Vol 73 (9) ◽  
pp. 1323-1338 ◽  
Author(s):  
Yuzo M. Chino
Keyword(s):  
Visual Cortex ◽  
Cortical Neurons ◽  
Time Course ◽  
Receptive Fields ◽  
Afferent Input ◽  
Contrast Threshold ◽  
Topographic Map ◽  
Retinal Lesions ◽  
Underlying Mechanisms ◽  
Adult Plasticity

When visual cortical neurons in adult mammals are deprived of their normal afferent input from retinae, they are capable of acquiring new receptive fields by modifying the effectiveness of existing intrinsic connections, a basis for topographic map reorganization. To gain insights into the underlying mechanisms and functional significance of this adult plasticity, we measured the spatial limits and time course of retinotopic map reorganization. We also determined whether reactivated neurons exhibit normal receptive field properties. We found that virtually all units in the denervated zone of cortex acquired new receptive fields (i.e., there were no silent areas in the cortex) and map reorganization can take place within hours of deafferentation provided that retinal lesions are relatively small (<5°). Furthermore, after long periods of recovery, reactivated units exhibited strikingly normal selectivity to stimulus orientation, direction of movement, and spatial frequency if relatively high contrast stimuli were used. However, responsiveness of these neurons, measured in terms of the maximum response amplitude and the contrast threshold, was clearly reduced. Thus, contrary to traditional belief, the adult visual cortex is capable of exhibiting considerable plasticity, and reactivated neurons are capable of contributing to an analysis of a visual scene.Key words: adult plasticity, visual cortex, retinal lesions, map reorganization, cat.

Topographic map reorganization in cat area 17 after early monocular retinal lesions

2002 ◽  
Vol 19 (1) ◽  
pp. 85-96 ◽  
Author(s):  
KAZUKI MATSUURA ◽  
BIN ZHANG ◽  
TAKAFUMI MORI ◽  
EARL L. SMITH ◽  
JON H. KAAS ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Receptive Fields ◽  
Optic Disk ◽  
Area 17 ◽  
Topographic Map ◽  
Retinal Lesions ◽  
The World ◽  
Blind Spots ◽  
Made In

Neither discrete peripheral retinal lesions nor the normal optic disk produces obvious holes in one's percept of the world because the visual brain appears to perceptually “fill in” these blind spots. Where in the visual brain or how this filling in occurs is not well understood. A prevailing hypothesis states that topographic map of visual cortex reorganizes after retinal lesions, which “sews up” the hole in the topographic map representing the deprived area of cortex (cortical scotoma) and may lead to perceptual filling in. Since the map reorganization does not typically occur unless retinotopically matched lesions are made in both eyes, we investigated the conditions in which monocular retinal lesions can induce comparable map reorganization. We found that following monocular retinal lesions, deprived neurons in cat area 17 can acquire new receptive fields if the lesion occurred relatively early in life (8 weeks of age) and the lesioned cats experienced a substantial period of recovery (>3 years). Quantitative determination of the monocular and binocular response properties of reactivated units indicated that responses to the lesioned eye for such neurons were remarkably robust, and that the receptive-field properties for the two eyes were generally similar. Moreover, excitatory or inhibitory binocular interactions were found in the majority of experimental units when the two eyes were activated together. These results are consistent with the hypothesis that map reorganization after monocular retinal lesions require experience-dependent plasticity and may be involved in the perceptual filling in of blind spots due to retinal lesions early in life.

scholarly journals Development of Thalamocortical Response Transformations in the Rat Whisker-Barrel System

2008 ◽  
Vol 99 (1) ◽  
pp. 356-366 ◽  
Author(s):  
Michael Shoykhet ◽  
Daniel J. Simons
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Receptive Fields ◽  
Second Phase ◽  
Adult Rats ◽  
Response Latencies ◽  
Thalamic Neurons ◽  
Response Properties ◽  
Temporal Domain

Extracellular single-unit recordings were used to characterize responses of thalamic barreloid and cortical barrel neurons to controlled whisker deflections in 2, 3-, and 4-wk-old and adult rats in vivo under fentanyl analgesia. Results indicate that response properties of thalamic and cortical neurons diverge during development. Responses to deflection onsets and offsets among thalamic neurons mature in parallel, whereas among cortical neurons responses to deflection offsets become disproportionately smaller with age. Thalamic neuron receptive fields become more multiwhisker, whereas those of cortical neurons become more single-whisker. Thalamic neurons develop a higher degree of angular selectivity, whereas that of cortical neurons remains constant. In the temporal domain, response latencies decrease both in thalamic and cortical neurons, but the maturation time-course differs between the two populations. Response latencies of thalamic cells decrease primarily between 2 and 3 wk of life, whereas response latencies of cortical neurons decrease in two distinct steps—the first between 2 and 3 wk of life and the second between the fourth postnatal week and adulthood. Although the first step likely reflects similar subcortical changes, the second phase likely corresponds to developmental myelination of thalamocortical fibers. Divergent development of thalamic and cortical response properties indicates that thalamocortical circuits in the whisker-to-barrel pathway undergo protracted maturation after 2 wk of life and provides a potential substrate for experience-dependent plasticity during this time.

scholarly journals Spatial Distribution of Contextual Interactions in Primary Visual Cortex and in Visual Perception

2000 ◽  
Vol 84 (4) ◽  
pp. 2048-2062 ◽  
Author(s):  
Mitesh K. Kapadia ◽  
Gerald Westheimer ◽  
Charles D. Gilbert
Keyword(s):  
Spatial Distribution ◽  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Human Perception ◽  
Spatial Arrangement ◽  
Orthogonal Axis ◽  
V1 Neurons ◽  
Contextual Interactions

To examine the role of primary visual cortex in visuospatial integration, we studied the spatial arrangement of contextual interactions in the response properties of neurons in primary visual cortex of alert monkeys and in human perception. We found a spatial segregation of opposing contextual interactions. At the level of cortical neurons, excitatory interactions were located along the ends of receptive fields, while inhibitory interactions were strongest along the orthogonal axis. Parallel psychophysical studies in human observers showed opposing contextual interactions surrounding a target line with a similar spatial distribution. The results suggest that V1 neurons can participate in multiple perceptual processes via spatially segregated and functionally distinct components of their receptive fields.

Simultaneous Reorganization in Thalamocortical Ensembles Evolves Over Several Hours After Perioral Capsaicin Injections

1999 ◽  
Vol 82 (2) ◽  
pp. 963-977 ◽  
Author(s):  
Donald B. Katz ◽  
S. A. Simon ◽  
Aaron Moody ◽  
Miguel A. L. Nicolelis
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Cortical Plasticity ◽  
Population Analysis ◽  
Receptive Fields ◽  
Somatosensory System ◽  
Spontaneous Firing ◽  
Neural Responses ◽  
Spatial Coupling ◽  
Neural Ensembles

Reorganization of the somatosensory system was quantified by simultaneously recording from single-unit neural ensembles in the whisker regions of the ventral posterior medial (VPM) nucleus of the thalamus and the primary somatosensory (SI) cortex in anesthetized rats before, during, and after injecting capsaicin under the skin of the lip. Capsaicin, a compound that excites and then inactivates a subset of peripheral C and Aδ fibers, triggered increases in spontaneous firing of thalamocortical neurons (10–15 min after injection), as well as rapid reorganization of the whisker representations in both the VPM and SI. During the first hour after capsaicin injection, 57% of the 139 recorded neurons either gained or lost at least one whisker response in their receptive fields (RFs). Capsaicin-related changes continued to emerge for ≥6 h after the injection: Fifty percent of the single-neuron RFs changed between 1–2 and 5–6 h after capsaicin injection. Most (79%) of these late changes represented neural responses that had remained unchanged in the first postcapsaicin mapping; just under 20% of these late changes appeared in neurons that had previously shown no plasticity of response. The majority of the changes (55% immediately after injection, 66% 6 h later) involved “unmasking” of new tactile responses. RF change rates were comparable in SI and VPM (57–49%). Population analysis indicated that the reorganization was associated with a lessening of the “spatial coupling” between cortical neurons—a significant reduction in firing covariance that could be related to distances between neurons. This general loss of spatial coupling, in conjunction with increases in spontaneous firing, may create a situation that is favorable for the induction of synaptic plasticity. Our results indicate that the selective inactivation of a peripheral nociceptor subpopulation can induce rapid and long-evolving (≥6 h) shifts in the balance of inhibition and excitation in the somatosensory system. The time course of these processes suggest that thalamic and cortical plasticity is not a linear reflection of spinal and brainstem changes that occur following the application of capsaicin.

scholarly journals Classical-contextual interactions in V1 may rely on dendritic computations

2018 ◽  
Author(s):  
Lei Jin ◽  
Bardia F. Behabadi ◽  
Monica P. Jadi ◽  
Chaithanya A. Ramachandra ◽  
Bartlett W. Mel
Keyword(s):  
Visual Cortex ◽  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Contextual Information ◽  
Flexible Substrate ◽  
Receptive Fields ◽  
Boundary Detection ◽  
Synaptic Interactions ◽  
Horizontal Connections ◽  
Local Circuits

AbstractA signature feature of the neocortex is the dense network of horizontal connections (HCs) through which pyramidal neurons (PNs) exchange “contextual” information. In primary visual cortex (V1), HCs are thought to facilitate boundary detection, a crucial operation for object recognition, but how HCs modulate PN responses to boundary cues within their classical receptive fields (CRF) remains unknown. We began by “asking” natural images, through a structured data collection and ground truth labeling process, what function a V1 cell should use to compute boundary probability from aligned edge cues within and outside its CRF. The “answer” was an asymmetric 2-D sigmoidal function, whose nonlinear form provides the first normative account for the “multiplicative” center-flanker interactions previously reported in V1 neurons (Kapadia et al. 1995, 2000; Polat et al. 1998). Using a detailed compartmental model, we then show that this boundary-detecting classical-contextual interaction function can be computed with near perfect accuracy by NMDAR-dependent spatial synaptic interactions within PN dendrites – the site where classical and contextual inputs first converge in the cortex. In additional simulations, we show that local interneuron circuitry activated by HCs can powerfully leverage the nonlinear spatial computing capabilities of PN dendrites, providing the cortex with a highly flexible substrate for integration of classical and contextual information.Significance StatementIn addition to the driver inputs that establish their classical receptive fields, cortical pyramidal neurons (PN) receive a much larger number of “contextual” inputs from other PNs through a dense plexus of horizontal connections (HCs). However by what mechanisms, and for what behavioral purposes, HC’s modulate PN responses remains unclear. We pursued these questions in the context of object boundary detection in visual cortex, by combining an analysis of natural boundary statistics with detailed modeling PNs and local circuits. We found that nonlinear synaptic interactions in PN dendrites are ideally suited to solve the boundary detection problem. We propose that PN dendrites provide the core computing substrate through which cortical neurons modulate each other’s responses depending on context.

scholarly journals Spiking Recurrent Networks as a Model to Probe Neuronal Timescales Specific to Working Memory

2019 ◽  
Author(s):  
Robert Kim ◽  
Terrence J. Sejnowski
Keyword(s):  
Working Memory ◽  
Recurrent Neural Networks ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Hierarchical Organization ◽  
Recurrent Networks ◽  
Multiple Timescales ◽  
Underlying Mechanisms ◽  
Experimental Findings ◽  
Long Timescales

AbstractCortical neurons process and integrate information on multiple timescales. In addition, these timescales or temporal receptive fields display functional and hierarchical organization. For instance, areas important for working memory (WM), such as prefrontal cortex, utilize neurons with stable temporal receptive fields and long timescales to support reliable representations of stimuli. Despite of the recent advances in experimental techniques, the underlying mechanisms for the emergence of neuronal timescales long enough to support WM are unclear and challenging to investigate experimentally. Here, we demonstrate that spiking recurrent neural networks (RNNs) designed to perform a WM task reproduce previously observed experimental findings and that these models could be utilized in the future to study how neuronal timescales specific to WM emerge.

Colour coding in the superior temporal sulcus of rhesus monkey visual cortex

1977 ◽  
Vol 197 (1127) ◽  
pp. 195-223 ◽  
Keyword(s):  
Visual Cortex ◽  
Corpus Callosum ◽  
Rhesus Monkey ◽  
Single Cells ◽  
Receptive Fields ◽  
Superior Temporal Sulcus ◽  
Afferent Input ◽  
Lateral Part ◽  
Anatomical Landmarks ◽  
Colour Coding

In the rhesus monkey, the posterior bank of the superior temporal sulcus forms part of the prestriate visual cortex and has two regions, a medial one and a lateral one, which have their own separate callosal connections. The afferent input to these two regions was studied in experiments where the corpus callosum was sectioned, and labelled amino acids were injected into other visual areas. By this method, it was found that area 17 projects to that part of the superior temporal sulcus occupied by the more medial of the two callosal inputs. By contrast, the part of the sulcus occupied by the more lateral callosal input was found to receive a strong projection from the fourth visual complex, an area rich in colour-coded cells. Recordings were made from single cells in the superior temporal sulcus in animals in which the corpus callosum had been sectioned previously. The degeneration produced by this procedure was used to provide anatomical landmarks enabling us to assign cells to the lateral or the medial regions of the sulcus. Such recordings revealed that receptive fields were topographically organized in the lateral part of the sulcus and that most cells were colour specific. By contrast, cells recorded from in the region of the more medial callosal patch within this sulcus were directionally selective, without any obvious colour coding. It was concluded from these combined anatomico-physiological experiments that there are at least two distinct regions in the superior temporal sulcus which have different afferent connections and functional properties.

scholarly journals Categorically distinct types of receptive fields in early visual cortex

2016 ◽  
Vol 115 (5) ◽  
pp. 2556-2576 ◽  
Author(s):  
Vargha Talebi ◽  
Curtis L. Baker
Keyword(s):  
Visual Cortex ◽  
System Identification ◽  
Cortical Neurons ◽  
Temporal Dynamics ◽  
High Reliability ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Natural Image ◽  
Visual Responses ◽  
Neurophysiological Studies

In the visual cortex, distinct types of neurons have been identified based on cellular morphology, response to injected current, or expression of specific markers, but neurophysiological studies have revealed visual receptive field (RF) properties that appear to be on a continuum, with only two generally recognized classes: simple and complex. Most previous studies have characterized visual responses of neurons using stereotyped stimuli such as bars, gratings, or white noise and simple system identification approaches (e.g., reverse correlation). Here we estimate visual RF models of cortical neurons using visually rich natural image stimuli and regularized regression system identification methods and characterize their spatial tuning, temporal dynamics, spatiotemporal behavior, and spiking properties. We quantitatively demonstrate the existence of three functionally distinct categories of simple cells, distinguished by their degree of orientation selectivity (isotropic or oriented) and the nature of their output nonlinearity (expansive or compressive). In addition, these three types have differing average values of several other properties. Cells with nonoriented RFs tend to have smaller RFs, shorter response durations, no direction selectivity, and high reliability. Orientation-selective neurons with an expansive output nonlinearity have Gabor-like RFs, lower spontaneous activity and responsivity, and spiking responses with higher sparseness. Oriented RFs with a compressive nonlinearity are spatially nondescript and tend to show longer response latency. Our findings indicate multiple physiologically defined types of RFs beyond the simple/complex dichotomy, suggesting that cortical neurons may have more specialized functional roles rather than lying on a multidimensional continuum.

A Computational Model of Perceptual Fill-in Following Retinal Degeneration

2008 ◽  
Vol 99 (5) ◽  
pp. 2086-2100 ◽  
Author(s):  
Justin N. J. McManus ◽  
Shimon Ullman ◽  
Charles D. Gilbert
Keyword(s):  
Human Subjects ◽  
Receptive Fields ◽  
Afferent Input ◽  
Visual Input ◽  
Cortical Region ◽  
Functional Changes ◽  
Retinal Lesions ◽  
Horizontal Connections ◽  
Perceptual Completion ◽  
Projection Zone

The ablation of afferent input results in the reorganization of sensory and motor cortices. In the primary visual cortex (V1), binocular retinal lesions deprive a corresponding cortical region [lesion projection zone (LPZ)] of visual input. Nevertheless, neurons in the LPZ regain responsiveness by shifting their receptive fields (RFs) outside the retinal lesions; this re-emergence of neural activity is paralleled by the perceptual completion of disrupted visual input in human subjects with retinal damage. To determine whether V1 reorganization can account for perceptual fill-in, we developed a neural network model that simulates the cortical remapping in V1. The model shows that RF shifts mediated by the plexus of spatial- and orientation-dependent horizontal connections in V1 can engender filling-in that is both robust and consistent with psychophysical reports of perceptual completion. Our model suggests that V1 reorganization may underlie perceptual fill-in, and it predicts spatial relationships between the original and remapped RFs that can be tested experimentally. More generally, it provides a general explanation for adaptive functional changes following CNS lesions, based on the recruitment of existing cortical connections that are involved in normal integrative mechanisms.

scholarly journals Pyramidal tract neurons receptive to different forelimb joints act differently during locomotion

2012 ◽  
Vol 107 (7) ◽  
pp. 1890-1903 ◽  
Author(s):  
Erik E. Stout ◽  
Irina N. Beloozerova
Keyword(s):  
Motor Cortex ◽  
Cortical Neurons ◽  
Pyramidal Tract ◽  
Receptive Fields ◽  
Close Relation ◽  
Afferent Input ◽  
The Body ◽  
Pyramidal Tract Neurons ◽  
Discharge Duration ◽  
Increased Activity

During locomotion, motor cortical neurons projecting to the pyramidal tract (PTNs) discharge in close relation to strides. How their discharges vary based on the part of the body they influence is not well understood. We addressed this question with regard to joints of the forelimb in the cat. During simple and ladder locomotion, we compared the activity of four groups of PTNs with somatosensory receptive fields involving different forelimb joints: 1) 45 PTNs receptive to movements of shoulder, 2) 30 PTNs receptive to movements of elbow, 3) 40 PTNs receptive to movements of wrist, and 4) 30 nonresponsive PTNs. In the motor cortex, a relationship exists between the location of the source of afferent input and the target for motor output. On the basis of this relationship, we inferred the forelimb joint that a PTN influences from its somatosensory receptive field. We found that different PTNs tended to discharge differently during locomotion. During simple locomotion shoulder-related PTNs were most active during late stance/early swing, and upon transition from simple to ladder locomotion they often increased activity and stride-related modulation while reducing discharge duration. Elbow-related PTNs were most active during late swing/early stance and typically did not change activity, modulation, or discharge duration on the ladder. Wrist-related PTNs were most active during swing and upon transition to the ladder often decreased activity and increased modulation while reducing discharge duration. These data suggest that during locomotion the motor cortex uses distinct mechanisms to control the shoulder, elbow, and wrist.

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