Abstract
Several psychophysical studies have shown that adaptation to different attributes of visual stimuli is modulated by attention. There is also evidence demonstrating that brief adaptation to an oriented grating impairs identification of nearby orientations by broadening orientation selectivity and changing the preferred orientation of individual V1 neurons(Dragoi et al, 2002). In this study, we investigated the effect of visual attention on brief orientation adaptation using resolvable and unresolvable patterns. In the first experiment, observers performed a delayed match-to-sample task in the peripheral visual field (at 10 deg of eccentricity) in attended versus non-attended condition. In the attended condition they were asked to report whether two briefly flashed Gabors, sample and test stimuli, differ in orientation or not. The test Gabor patch was preceded by a 400 ms resolvable adapting stimulus. In the non-attended condition, observers performed the same task concurrent with a secondary task (even/odd judgment) at the fixation point during the adaptation period. The second experiment was identical in all respects to the first experiment, except that unresolvable Gabor patches were used in the adaptation phase. Results in both experiments showed orientation-selective adaptation in the attended condition but no adaptation in the non-attended condition. We suggest that unresolvable oriented patterns could activate the primary visual cortex and that this activation (as revealed by brief orientation adaptation paradigm) is modulated by attention.