Late positive component correlates of verbal and visuospatial processing.

Bilateral VERs were elicited by letter stimuli requiring verbal processing and patterns requiring visuospatial processing in a go/no-go reaction time paradigm. The VERS were formed separately to the targets and non-targets of each stimulus type. No VER component displayed hemisphere asymmetries which varied in a task-dependent fashion. However P150 latency was found to be shorter, and N150 amplitude larger, in VERs recorded from the right hemisphere. This is considered to reflect the superiority of the right hemisphere for the early stages of the processing of visual input. P400 latency was shorter and its amplitude larger to the pattern stimuli. In addition, subjects' reaction times were shorter to these stimuli. These results were interpreted in evidence supporting the notion that the late positive component of the ER reflects processes of stimulus evaluation which are not necessarily correlated with those of response selection and execution.