Visual information processing with brain potentials that accompany saccadic eye movements.

The relation between stimulus probability and the late components of the saccade-related brain (lambda) potentials (SRPs) was studied in three kinds of cognitive tasks: guessing, counting and word categorization. These tasks, traditionally used to study event-related potentials, were modified in such a way that subjects had to perform a saccadic eye movement in order to perceive the target stimulus. In guessing and counting tasks three kinds of target stimulus appeared with the probabilities of 17, 33 and 50 percent, respectively. In the semantic word categorization task the stimuli belonged to one of two categories: frequent (80 percent, female names) and infrequent (20 percent, male names). In all three tasks the late positive components (P300 and P4) had greater amplitudes of SRPs elicited by the infrequent stimuli than by the frequent ones. A Principal Component-Varimax Analysis of the SRP data revealed factors corresponding to (1) a positive Slow Wave, (2) the positive P300 and (3) the P4 components, respectively. In addition, the semantic categorization task was correlated with a late (negative) SRP component.