Intraoperative frontal eye field stimulation elicits ocular deviation and saccade suppression

Cortical stimulation is a useful way of elucidating the cortical control of eye movements. The aim of this study was to determine the type of eye movements evoked in response to intraoperative electrical stimulation of the frontal eye field (FEF) region in a fully awake patient during surgery for a frontal lobe glioma. A train of low-intensity electrical pulses within an area in the precentral gyrus evoked contraversive smooth eye movements (SEM) recorded electro-oculographically. Stimulation of an anterior sub-region of this electrically determined FEF disclosed both SEM and suppression of self-paced saccades. However, electrical stimulation of this region evoked no saccades in agreement with pre-operative fMRI using a self-paced saccade paradigm, which did not show activation within the ipsilateral FEF. In humans, intraoperative FEF stimulation may elicit recordable contraversive SEM, and interfere with oculomotor behaviour, suppressing self-paced saccades.