[Visual evoked potentials to illusory contours (Kanizsa's square)]

Visual evoked potentials (VEP) were studied in 10 subjects to presentation of illusory Kanizsa's square and control visual stimulus with similar spatial organization, which did not produce a visual illusion. The VEPs to the applied stimuli were expressed in the occipital, parietal, and inferiotemporal areas. It was shown that during presentation of the illusory configuration the amplitude of VEP variation between the N180 and P230 peaks was higher and the N300 latency lower than during presentation of stimuli with real configuration. The difference between VEPs in amplitude were observed in the left and right occipital and left inferiotemporal areas, and differences in latency were pronounced in the left occipital derivation. It is suggested that there exist two contour-encoding regions in the visual system which participate in different kinds of the visual analysis. First, associative visual fields which encode the information on single sings and their complexes and inferiotemporal fields which compare the sensory and memory codes.