Transcranial magnetic stimulation of the prefrontal cortex delays contralateral endogenous saccades

The contributions of the superior prefrontal cortex (SPFC) and the superior parietal lobule (SPL) in generating voluntary endogenous and reflexive visually guided saccades were investigated using transcranial magnetic stimulation (TMS). Subjects made choice saccades to the left or right visual field in response to a central arrowhead (endogenous go signal) or a peripheral asterisk (exogenous go signal) that were presented 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 were observed when the go signal was exogenous and TMS was over the SPFC or when TMS was over the SPL for either saccade type. The delayed contralateral endogenous saccades observed in this study are likely a consequence of disruption in the normal operations of the human frontal eye field.