Plasticity of Receptive Fields in Early Stages of the Adult Visual System

2002 ◽  
Keyword(s):  
Visual System ◽  
Receptive Fields ◽  
Early Stages

Coding Principles in Adaptation

2019 ◽  
Vol 5 (1) ◽  
pp. 427-449 ◽  
Author(s):  
Alison I. Weber ◽  
Kamesh Krishnamurthy ◽  
Adrienne L. Fairhall
Keyword(s):  
Nervous System ◽  
Visual System ◽  
Functional Role ◽  
Receptive Fields ◽  
Sensory Systems ◽  
Spike Frequency Adaptation ◽  
Theoretical Frameworks ◽  
Different Types ◽  
Common Principle

Adaptation is a common principle that recurs throughout the nervous system at all stages of processing. This principle manifests in a variety of phenomena, from spike frequency adaptation, to apparent changes in receptive fields with changes in stimulus statistics, to enhanced responses to unexpected stimuli. The ubiquity of adaptation leads naturally to the question: What purpose do these different types of adaptation serve? A diverse set of theories, often highly overlapping, has been proposed to explain the functional role of adaptive phenomena. In this review, we discuss several of these theoretical frameworks, highlighting relationships among them and clarifying distinctions. We summarize observations of the varied manifestations of adaptation, particularly as they relate to these theoretical frameworks, focusing throughout on the visual system and making connections to other sensory systems.

The Detection of Orientation of Small Objects

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 59-59
Author(s):  
J M Zanker ◽  
M P Davey
Keyword(s):  
Visual Field ◽  
Visual System ◽  
Computer Simulations ◽  
Visual Information ◽  
Human Performance ◽  
Receptive Fields ◽  
Experimental Result ◽  
Orientation Tuning ◽  
Basic Question ◽  
Visual Stream

Visual information processing in primate cortex is based on a highly ordered representation of the surrounding world. In addition to the retinotopic mapping of the visual field, systematic variations of the orientation tuning of neurons are described electrophysiologically for the first stages of the visual stream. On the way to understanding the relation of position and orientation representation, in order to give an adequate account of cortical architecture, it will be an essential step to define the minimum spatial requirements for detection of orientation. We addressed the basic question of spatial limits for detecting orientation by comparing computer simulations of simple orientation filters with psychophysical experiments in which the orientation of small lines had to be detected at various positions in the visual field. At sufficiently high contrast levels, the minimum physical length of a line whose orientation can just be resolved is not constant when presented at various eccentricities, but covaries inversely with the cortical magnification factor. A line needs to span less than 0.2 mm on the cortical surface in order to be recognised as oriented, independently of the actual eccentricity at which the stimulus is presented. This seems to indicate that human performance for this task approaches the physical limits, requiring hardly more than approximately three input elements to be activated, in order to detect the orientation of a highly visible line segment. Combined with the estimates for receptive field sizes of orientation-selective filters derived from computer simulations, this experimental result may nourish speculations of how the rather local elementary process underlying orientation detection in the human visual system can be assembled to form much larger receptive fields of the orientation-sensitive neurons known to exist in the primate visual system.

scholarly journals Orientation tuning depends on spatial frequency in mouse visual cortex

2016 ◽  
Author(s):  
Inbal Ayzenshtat ◽  
Jesse Jackson ◽  
Rafael Yuste
Keyword(s):  
Visual Cortex ◽  
Spatial Frequency ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Receptive Fields ◽  
Orientation Selectivity ◽  
Natural Scenes ◽  
Response Properties ◽  
Layer 2 ◽  
Mouse Visual Cortex

AbstractThe response properties of neurons to sensory stimuli have been used to identify their receptive fields and functionally map sensory systems. In primary visual cortex, most neurons are selective to a particular orientation and spatial frequency of the visual stimulus. Using two-photon calcium imaging of neuronal populations from the primary visual cortex of mice, we have characterized the response properties of neurons to various orientations and spatial frequencies. Surprisingly, we found that the orientation selectivity of neurons actually depends on the spatial frequency of the stimulus. This dependence can be easily explained if one assumed spatially asymmetric Gabor-type receptive fields. We propose that receptive fields of neurons in layer 2/3 of visual cortex are indeed spatially asymmetric, and that this asymmetry could be used effectively by the visual system to encode natural scenes.Significance StatementIn this manuscript we demonstrate that the orientation selectivity of neurons in primary visual cortex of mouse is highly dependent on the stimulus SF. This dependence is realized quantitatively in a decrease in the selectivity strength of cells in non-optimum SF, and more importantly, it is also evident qualitatively in a shift in the preferred orientation of cells in non-optimum SF. We show that a receptive-field model of a 2D asymmetric Gabor, rather than a symmetric one, can explain this surprising observation. Therefore, we propose that the receptive fields of neurons in layer 2/3 of mouse visual cortex are spatially asymmetric and this asymmetry could be used effectively by the visual system to encode natural scenes.Highlights–Orientation selectivity is dependent on spatial frequency.–Asymmetric Gabor model can explain this dependence.

scholarly journals Energy saving in vision at the first synapse: The ON and OFF pathways measure temporal differences

2017 ◽  
Author(s):  
Bart M. ter Haar Romeny
Keyword(s):  
Visual System ◽  
Receptive Fields ◽  
Dendritic Tree ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Inner Plexiform Layer ◽  
Surveillance Camera ◽  
Starburst Amacrine Cells ◽  
Spatio Temporal ◽  
On And Off Pathways

AbstractThe inner plexiform layer (IPL) of mammalian retina has a precise bisublaminar organization in an inner on- and an outer off-layer, innervated by spatially segregated on- and off-cone bipolar cell inputs. Also, the processes of starburst amacrine cells are segregated into on and off sublaminae of the IPL. Distances between overlapping on-off pair retinal ganglion cell dendritic tree centers are markedly smaller than between on-on or off-off centers, indicating simultaneously sampling the same space. Despite dekades of research, no good model exists for the role of the on- and off pathways. Here I propose that the on- and off pairs are temporally subtracted, with one channel delayed in time, likely in a higher cortical center. The on- and off receptive fields give at every retinal location an I+ and I-signal, where I is intensity, velocity, color. Subsequent frame subtraction is a basis function of every surveillance camera for vision, and in MPEG video/sound compression. The model explains the many phenomena observed when the retinal image is stabilized. The separation of layers in the LGN fits with the notion of a time delay at higher cortical level. The directionalty observed in micro-saccades is typically perpendicular to the main edges in the scene. Precise measurement of spatio-temporal receptive field kernels shows that time is processed in the visual system as a real-time process, i.e. with a logarithmic time axis. As only contours and textures are transmitted, it is a very effective design strategy of the visual system to conserve energy, in a brain that typically uses 25 Watt and very low neuron firing frequencies. The higher visual centers perform the fill-in (inpainting) with such efficiency, that the subtraction always goes unnoticed.

Dark Adaptation as a Model of the Parkinsonian Visual System

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 48-48
Author(s):  
B Wink ◽  
J P Harris
Keyword(s):  
Spatial Frequency ◽  
Visual System ◽  
Dark Adaptation ◽  
Peripheral Vision ◽  
Receptive Fields ◽  
High Spatial Frequency ◽  
Normal Subjects ◽  
Apparent Contrast ◽  
Contrast Gain ◽  
Spatial Frequencies

It has been suggested that the Parkinsonian visual system is like the normal visual system, but is inappropriately dark-adapted (Beaumont et al, 1987 Clinical Vision Sciences2 123 – 129). Thus it is of interest to ask to what extent dark adaptation of normal subjects produces visual changes like those of Parkinson's disease (PD). One such change is the reduction in apparent contrast of medium and high spatial frequencies in peripheral vision in the illness (Harris et al, 1992 Brain115 1447 – 1457). Normal subjects judged whether the contrast of a peripherally viewed grating was higher or lower than that of a foveally viewed grating, and a staircase technique was used to estimate the point of subjective equality. Judgements were made at four spatial frequencies (0.5 to 4.0 cycles deg−1) and four contrasts (8.0% to 64%). The display, the mean luminance of which was 26 cd m−2, was viewed through a 1.5 lu nd filter in the relatively dark-adapted condition. The ANOVA showed an interaction between dark adaptation and the spatial frequency of the gratings. Dark adaptation reduces the apparent contrast of high-spatial-frequency gratings, an effect which is greater at lower contrasts. This mimics the effect found with PD sufferers, and suggests that dark adaptation may provide a useful model of the PD visual system. In a second experiment, the effect of dark adaptation on the relationship between apparent spatial frequency in the fovea and periphery was investigated. The experiment was similar to the first, except that judgements were made about the apparent spatial frequency, rather than the contrast, of the peripheral grating. ANOVA showed no differential effect of dark adaptation on the apparent spatial frequency of the peripheral grating. This suggests that the observed reduction in apparent contrast of the peripheral gratings in dark-adapted normals and Parkinson's sufferers may reflect relative changes in contrast gain, rather than relative changes in the spatial organisation of receptive fields.

8. The physiology and anatomy of the visual system

2017 ◽  
pp. 123-143
Author(s):  
Brian Rogers
Keyword(s):  
Information Processing ◽  
Visual Cortex ◽  
Visual System ◽  
Lateral Inhibition ◽  
Visual Information ◽  
Receptive Fields ◽  
Neural Pathways ◽  
Human Retina ◽  
Feature Detectors ◽  
System P

‘The physiology and anatomy of the visual system’ describes what we have learned from neurophysiology and anatomy over the past eighty years and what this tells us about the meaning of the circuits involved in visual information processing. It explains how psychologists and physiologists use the terms ‘mechanism’ and ‘process’. For physiologists, a mechanism is linked to the actions of individual neurons, neural pathways, and the ways in which the neurons are connected up. For psychologists, the term is typically used to describe the processes the neural circuits may carry out. The human retina is described with explanations of lateral inhibition, receptive fields, and feature detectors as well as the visual cortex and different visual pathways.

Single cells in the visual system and images past

2002 ◽  
Vol 25 (2) ◽  
pp. 200-201
Author(s):  
Glenn E. Meyer
Keyword(s):  
Visual System ◽  
Single Cell ◽  
Entorhinal Cortex ◽  
Single Cells ◽  
Receptive Fields ◽  
Parahippocampal Gyrus ◽  
Area 17 ◽  
Related Activity

Various techniques have attempted to localize imagery. However, early findings using single cell recordings of human receptive fields during imagery tasks have had little impact. Reports by Marg and his coworkers (1968) found no evidence for imagery in human Area 17, 18, and 19. Single cells from humans suggest later imagery-related activity in hippocampus, amygdala, entorhinal cortex, and parahippocampal gyrus.

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