Orientation column

About: Orientation column is a research topic. Over the lifetime, 1142 publications have been published within this topic receiving 130169 citations.

Nonlinear Y-Like Receptive Fields in the Early Visual Cortex: An Intermediate Stage for Building Cue-Invariant Receptive Fields from Subcortical Y Cells.

Abstract: Many of the neurons in early visual cortex are selective for the orientation of boundaries defined by first-order cues (luminance) as well as second-order cues (contrast, texture). The neural circuit mechanism underlying this selectivity is still unclear, but some studies have proposed that it emerges from spatial nonlinearities of subcortical Y cells. To understand how inputs from the Y-cell pathway might be pooled to generate cue-invariant receptive fields, we recorded visual responses from single neurons in cat Area 18 using linear multielectrode arrays. We measured responses to drifting and contrast-reversing luminance gratings as well as contrast modulation gratings. We found that a large fraction of these neurons have nonoriented responses to gratings, similar to those of subcortical Y cells: they respond at the second harmonic (F2) to high-spatial frequency contrast-reversing gratings and at the first harmonic (F1) to low-spatial frequency drifting gratings (“Y-cell signature”). For a given neuron, spatial frequency tuning for linear (F1) and nonlinear (F2) responses is quite distinct, similar to orientation-selective cue-invariant neurons. Also, these neurons respond to contrast modulation gratings with selectivity for the carrier (texture) spatial frequency and, in some cases, orientation. Their receptive field properties suggest that they could serve as building blocks for orientation-selective cue-invariant neurons. We propose a circuit model that combines ON- and OFF-center cortical Y-like cells in an unbalanced push–pull manner to generate orientation-selective, cue-invariant receptive fields. SIGNIFICANCE STATEMENT A significant fraction of neurons in early visual cortex have specialized receptive fields that allow them to selectively respond to the orientation of boundaries that are invariant to the cue (luminance, contrast, texture, motion) that defines them. However, the neural mechanism to construct such versatile receptive fields remains unclear. Using multielectrode recording, we found a large fraction of neurons in early visual cortex with receptive fields not selective for orientation that have spatial nonlinearities like those of subcortical Y cells. These are strong candidates for building cue-invariant orientation-selective neurons; we present a neural circuit model that pools such neurons in an imbalanced “push–pull” manner, to generate orientation-selective cue-invariant receptive fields.

Edge-Related Activity Is Not Necessary to Explain Orientation Decoding in Human Visual Cortex.

Abstract: Multivariate pattern analysis is a powerful technique; however, a significant theoretical limitation in neuroscience is the ambiguity in interpreting the source of decodable information used by classifiers. This is exemplified by the continued controversy over the source of orientation decoding from fMRI responses in human V1. Recently Carlson (2014) identified a potential source of decodable information by modeling voxel responses based on the Hubel and Wiesel (1972) ice-cube model of visual cortex. The model revealed that activity associated with the edges of gratings covaries with orientation and could potentially be used to discriminate orientation. Here we empirically evaluate whether “edge-related activity” underlies orientation decoding from patterns of BOLD response in human V1. First, we systematically mapped classifier performance as a function of stimulus location using population receptive field modeling to isolate each voxel9s overlap with a large annular grating stimulus. Orientation was decodable across the stimulus; however, peak decoding performance occurred for voxels with receptive fields closer to the fovea and overlapping with the inner edge. Critically, we did not observe the expected second peak in decoding performance at the outer stimulus edge as predicted by the edge account. Second, we evaluated whether voxels that contribute most to classifier performance have receptive fields that cluster in cortical regions corresponding to the retinotopic location of the stimulus edge. Instead, we find the distribution of highly weighted voxels to be approximately random, with a modest bias toward more foveal voxels. Our results demonstrate that edge-related activity is likely not necessary for orientation decoding. SIGNIFICANCE STATEMENT A significant theoretical limitation of multivariate pattern analysis in neuroscience is the ambiguity in interpreting the source of decodable information used by classifiers. For example, orientation can be decoded from BOLD activation patterns in human V1, even though orientation columns are at a finer spatial scale than 3T fMRI. Consequently, the source of decodable information remains controversial. Here we test the proposal that information related to the stimulus edges underlies orientation decoding. We map voxel population receptive fields in V1 and evaluate orientation decoding performance as a function of stimulus location in retinotopic cortex. We find orientation is decodable from voxels whose receptive fields do not overlap with the stimulus edges, suggesting edge-related activity does not substantially drive orientation decoding.

Development of cortical afferents and cortico-tectal efferents of the mammalian (rat) primary visual cortex.

Abstract: At the time when the fibres from the striate cortex (area 17) begin to innervate the superficial layers of the superior colliculus of the young rat (postnatal days 4 and 5) a high degree of specificity in the organization of this newly formed cortico-tectal projection is already apparent. Thus, in young rats, as in adult mammals of virtually all species studied so far, the somata of cortico-tectal neurones are confined to lamina V of the ipsilateral cortex. However, this high degree of laminar (radial) specificity in young animals is accompanied by a substantial degree of exuberance as indicated by a tangential distribution of the cortico-tectal cells which is wider than that in the adult. The exuberant projections are pruned during the second postnatal week. The cortico-cortical associational and commissural fibres start to enter the grey matter of the rat striate cortex after postnatal day 7. Again a high degree of specificity in the laminar distribution of those newly established projections is apparent. However, the cortico-cortical projection, at the time when cortico-cortical fibres enter the cortical laminae, is clearly exuberant since the tangential spread of cortical cells projecting to the striate cortex is wider than that in the adult. Pruning of these excessive projections takes place some time after postnatal day 14. It is believed that understanding the mechanism(s) underlying the development of connections of the rat visual cortex might be of general importance in understanding developmental abnormalities in the pattern of interconnections of the visual cortices of other mammalian orders.

Spatial periodicities of periodic complex cells in the visual cortex cluster at one-half octave intervals.

Abstract: Within individual penetrations in the visual cortex, spatial periodicities of periodic complex cells differ by either one-half or one octave When data are pooled from neurons subserving the central visual area in many cats, the results indicate that spatial periodicities cluster at one-half octave intervals over a 2 1/2-octave range (095 to 54 cyc/deg) Thus a relatively small number of such channels spaced at regular intervals along a logarithmic scale within each orientation column may suffice for this stage of spatial processing