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Chang'an Zhan McGill, Curtis L. Baker; Cortical orientation domains are invariant with carrier type for contrast envelopes. Journal of Vision 2004;4(8):277. doi: 10.1167/4.8.277.
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© ARVO (1962-2015); The Authors (2016-present)
We have recently demonstrated (Zhan & Baker, 2003) highly similar cortical orientation domains for three kinds of stimuli (sinewave gratings, contrast envelopes, and illusory contours) differing in the type of stimulus attribute being modulated (luminance, contrast, and phase, respectively). We now ask whether the orientation domains for contrast envelopes are dependent on the nature of the carrier texture whose contrast is modulated. We have used intrinsic signal optical imaging to compare the spatial organization of orientation domains in cat A18 for 4 kinds of contrast envelopes, which differed in their carrier types — 1D sinewave gratings, regular checkerboards, random check noise, and 2D fractal noise. The envelope spatial frequencies were in the optimal range as for first-order stimuli (0.065–0.15 cpd). Although these carriers differed qualitatively in their power spectra (as well as appearance), we found invariant orientation domains as long as the carrier spatial frequencies (0.652–1.3 cpd) were outside the luminance passband for the measured cortical area. All these stimuli activated similar orientation domains as first-order visual stimuli, as demonstrated by near-zero differential orientation maps, and near-unity correlation coefficients between all the orientation maps. Together with the previous study, these results suggest that the neurons responsive to different kinds of orientation contours are evenly distributed across A18, and that coarse-scale orientation is coded by anatomical domains which are invariant to the composition of the oriented stimuli.
Canadian CIHR Grant MOP 9685 to CLB
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