Cortical oscillatory responses do not affect visual segmentation

We tested the hypothesis that synchronization of oscillatory responses between populations of visually driven neurons could be the basis for visual segmentation and perceptual grouping. We reasoned that oscillations in response induced by flickering visual targets should have an effect on visual performance in these tasks. We therefore measured the psychophysical performance of human subjects in a texture segregation task (Expt I) and in a perceptual grouping task (Expt II). In both experiments, the elements composing the stimuli were flickered and presented in a variety of flicker conditions. These experimental conditions were designed to either interfere with naturally occuring synchronization of oscillations, or to induce synchronization and bias a subject's perceptual judgment. Performance in these tasks was neither helped nor hindered by the temporal pattern of flicker. These results suggest that physiologically observed oscillatory responses are unrelated to the processes underlying visual segmentation and perceptual grouping.