Evidence for mechanisms sensitive to localised orientation regularity: An adaptation study A Ahmed1, I Mareschal2, T L Watson3 |
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1MARCS, University of Western Sydney, Australia |
| A recent study by Morgan, Mareschal, Chubb & Solomon [2012, Proc Biol Sci., 279(1739), 2754-60] has provided evidence for mechanisms in the visual system sensitive to the positional regularity of elements within a grid. Similar mechanisms for the assessment of the regularity of orientation of elements have not yet been explored. Here we assess whether these mechanisms are susceptible to adaptation. Using arrays of Gabor patches via which orientation variance was manipulated and a 2AFC variance discrimination task we show that exposure to a Gabor array with a particular orientation variance does affect perceived regularity. Without the presentation of an adapter arrays with orientation variance below 0.07 radians (standard deviation of a Gaussian distribution) were indistinguishable from zero variance arrays. When observers were exposed to high variance or random adapters the perceived regularity of subsequent arrays increased (p<0.05, n=6) while zero variance adapters decreased perceived regularity (p<0.05, n=6). Additionally, no adaptation was observed when the mean orientation of the adapter was orthogonal to that of the test array. This suggests that the mechanism via which we assess variance in local orientation elements is tuned for global orientation. |
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