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Contrast independence of cardinal preference: stable oblique effect in orientation maps of ferret visual cortex

Grabska-Barwinska, A; Distler, C; Hoffmann, KP; Jancke, D; (2009) Contrast independence of cardinal preference: stable oblique effect in orientation maps of ferret visual cortex. EUR J NEUROSCI , 29 (6) 1258 - 1270. 10.1111/j.1460-9568.2009.06656.x.

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Abstract

The oblique effect was first described as enhanced detection and discrimination of cardinal orientations compared with oblique orientations. Such biases in visual processing are believed to originate from a functional adaptation to environmental statistics dominated by cardinal contours. At the neuronal level, the oblique orientation effect corresponds to the numerical overrepresentation and narrower tuning bandwidths of cortical neurons representing the cardinal axes. The anisotropic distribution of orientation preferences over large cortical regions was revealed with optical imaging, providing further evidence for the cortical oblique effect in several mammalian species. Our present study explores whether the dominant representation of cardinal contours persists at different stimulus contrasts. Performing intrinsic optical imaging in the ferret visual cortex and presenting drifting gratings at various orientations and contrasts (100%, 30% and 10%), we found that the overrepresentation of vertical and horizontal contours was invariant across stimulus contrasts. In addition, the responses to cardinal orientations were also more robust and evoked larger modulation depths than responses to oblique orientations. We conclude that orientation maps remain constant across the full range of contrast levels down to detection thresholds. Thus, a stable layout of the functional architecture dedicated to processing oriented edges seems to reflect a fundamental coding strategy of the early visual cortex.

Type:Article
Title:Contrast independence of cardinal preference: stable oblique effect in orientation maps of ferret visual cortex
DOI:10.1111/j.1460-9568.2009.06656.x
Keywords:anisotropy, oblique effect, orientation tuning, striate cortex, CAT STRIATE CORTEX, CORTICAL AREA 21A, STIMULUS ORIENTATION, RESPONSE FUNCTION, NATURAL IMAGES, FUNCTIONAL-ORGANIZATION, HORIZONTAL CONNECTIONS, UNEQUAL REPRESENTATION, DIRECTION SELECTIVITY, TEMPORAL FREQUENCY
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Life Sciences > Gatsby Computational Neuroscience Unit

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