TRANSCRANIAL MAGNETIC STIMULATION OF THE PREFRONTAL CORTEX DELAYS CONTRALATERAL ENDOGENOUS SACCADES

The contributions of the superior prefrontal cortex (SPFC) and the sup erior parietal lobule (SPL) in generating voluntary endogenous and ref lexive visually guided saccades were investigated using transcranial m agnetic stimulation (TMS). Subjects made choice saccades to the left o r right visual field in response to a central arrowhead (endogenous go signal) or a peripheral asterisk (exogenous go signal) that were pres ented along with a single TMS pulse at varying temporal intervals. TMS over the SPFC increased latencies for saccades made in response to an endogenous go signal toward the contralateral hemifield. No effects w ere observed when the go signal was exogenous and TMS was over the SPF C or when TMS was over the SPL for either saccade type. The delayed co ntralateral endogenous saccades observed in this study are likely a co nsequence of disruption in the normal operations of the human frontal eye field.