Topic
Orientation column
About: Orientation column is a research topic. Over the lifetime, 1142 publications have been published within this topic receiving 130169 citations.
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01 Jan 2006
TL;DR: The capacity of the visual system to reorganize appears to extend throughout life, and suggests that the apparent stability of this system under normal conditions is the consequence of a counter-balancing of factors that could cause change.
Abstract: The visual systems of mammals, like the somatosensory and auditory systems, consist of a hierarchy of nuclei and cortical areas that represent receptor surfaces in topographic patterns (Felleman and Van Essen, 1991; Bullier, 2004; Rosa and Tweedale, 2004). The question raised here is what happens to the pattern of representation when part of the activating inputs to one of these levels has been removed. The basic answer for all of these sensoryperceptual systems is that the deprived zones of neurons usually do not remain unresponsive to sensory stimuli. Instead, they recover responsiveness to remaining inputs that always activated other pools of neurons, but were previously ineffective sources of activation for the pool of neurons that became deprived (Kaas and Florence, 2001). The visual system is especially interesting in this regard, because neurons across binocular positions of visual cortex are responsive to two receptor surfaces, the visually matched positions of the retina of each eye. Thus, it is possible to totally deprive parts of the cortical representation of normal sources of visual activation, or deprive these parts of the sources of activation from only one eye. Both types of deprivation, as well as deprivations of higher visual centers by small lesions of primary visual cortex, reveal cryptic features of visual system organization, as well as the capacity of deprived neurons to acquire new sources of activation. This capacity of the visual system to reorganize appears to extend throughout life, and suggests that the apparent stability of this system under normal conditions is the consequence of a counter-balancing of factors that could cause change.
4 citations
01 Jan 1990
4 citations
TL;DR: The orientation domain thus embodies a three stage visual contour processor in V1, and it is suggested that these zones subseries computation of distinct aspects of visual contours (linear orientation, local curvature, and contour singularities).
Abstract: PURPOSE: In the mammalian visual system, early stages of visual form perception begin with orientation selective neurons in primary visual cortex (V1). In many species (including humans, monkeys, tree shrews, cats, and ferrets), these neurons are organized in beautifully arrayed orientation columns, which shift in orientation preference across V1 and are highlighted by orientation pinwheels. However, to date, the relationship of orientation architecture to the encoding of elemental aspects of visual contours is still unknown.
METHODS: Using a novel highly accurate method of targeting electrode position, combining with optical image and single-unit recording, we report for the first time the presence of three functionally distinct zones within single orientation domains.
RESULTS: We found evidence for three concentric sub-regions centered on the orientation-pinwheel. The central-most region contains neurons with small receptive fields and strong suppressive surrounds, while the outermost region contains neurons with larger receptive fields and weak suppressive surrounds.
CONCLUSIONS: We suggest that these zones subseries computation of distinct aspects of visual contours (linear orientation, local curvature, and contour singularities). The orientation domain thus embodies a three stage visual contour processor in V1.
4 citations
TL;DR: It is demonstrated that sharp and contrast–invariant orientation tuning curves are combined with contrast saturation, the strength of cortical amplification can be localized in orientation space and anisotropic contextual suppression by iso-oriented flanking stimuli arises as an emergent property and can be mediated by local connections.
4 citations
Journal Article•
TL;DR: It is suggested that cortical spatial summation nonlinearities are not functionally derived from input Y cell non linearities, and in particular not in the nonlinear complex cells.
Abstract: Retinal ganglion and lateral geniculate cells of the primary visual pathway may be categorized as X or Y according to their spatial linearity summation properties In particular, Y cell spatial-frequency transfer functions have a distinctive spatial--linearity signature Their receptive fields comprise a temporally and spatially linear mechanism (center plus antagonistic surround) that responds to relatively low spatial frequency stimuli, and a temporally nonlinear mechanism, coextensive with the linear mechanism, that--though broad in extent--responds best to high spatial-frequency stimuli This component exhibits spatially nonlinear properties We looked for this Y cell signature in cat visual cortical cells If the predominant excitatory input to a certain type of cortical cell were from lateral geniculate nucleus (LGN) Y cells, we would expect to find the Y cell signature underlying the cortical cell transfer function However, we have not found this Y cell signature in any of the cortical cell studied, and in particular not in the nonlinear complex cells This would suggest that cortical spatial summation nonlinearities are not functionally derived from input Y cell nonlinearities
4 citations