Hemispheric lateralization of event-related potentials in a cued reaction-time task

Abstract

Subjects were tested in a cued reaction-time task wherein warning stimuli (S 1) of 5-letter words or dot patterns inter-mixed across trials were briefly presented. After 2 sec a second stimulus (S 2) of the same category as the S 1 appeared and the subject pressed a key with the left or right hand. The right key was pressed if S 2 was a synonym of S 1 or if the second dot pattern was the same as the first. The left key was pressed for antonyms or different patterns. It was predicted that CNVs would be larger over the left than right hemisphere on word trials and vice-versa on pattern trials in accordance with speculations concerning hemispheric specialization. The CNV was lateralized as expected, most prominently on pattern trials. In addition a negative transient evoked by S 2, and a late negative post-imperative slow wave were similarly lateralized. P 300 waves were very large and largest to the S 2 when it differed from S 1 Factor analysis confirmed these results and indicated, in addition, that P 300 was larger in the hemisphere least relevant to the task.