[Visual search and event-related potentials in the extrastriate cortical areas in humans].

Parameters of visual search (reaction time, mistakes) were investigated in 11 young healthy volunteers, under changing parameters of target symbol (form, color and location) in surroundings of white distracters (flankers). In 6 cortical leads: P3, P4, T3, T4, T5, T6, monopolar event-related potentials (ERPs) were registered and analyzed for the late endogenous components: N2, P3, because these very components have changed under verifying of search (so called late selection). In the hard search (similar target and distractors) the increase of search time was accompanied by the delay of P3 component and diminishing of its amplitude. The definite (the knowledge of) target position resulted by the decrease search time and decrease of P3 wave latency as compared with situation of uncertainty in respect to the position of target. Alteration of the target stimulus colour were led to abolishment (cancel) of inhibition effect of distracters: parameters of IRP have not differed from parameters of ERPs to solid target stimulus without the flankers. A high correlation of search time and parameters of P3 wave was revealed. Changes of IRPs in different kinds of search were similar in parietal and temporal leads. This suggests that the parietal and temporal cortical areas function as united system, under search of target in environment.