Stimulation-evoked saccades from the dorsomedial frontal cortex of the rhesus monkey following lesions of the frontal eye fields and superior colliculus.

This study examined whether signals for the generation of eye movements from the dorsomedial frontal cortex (DMFC) reach brainstem oculomotor centers either through the frontal eye fields (FEF) or through the superior colliculi (SC). The DMFC was stimulated when the monkeys studied were intact and after either one FEF or one SC was ablated. Following lesions of either the FEF or SC, the topographic order of the DMFC was largely preserved. After either lesions, stimulation of anterior DMFC sites still evoked saccades that terminated in contralateral space, and stimulation of posterior DMFC sites still evoked saccades that terminated in central space. The probability of evoking saccades decreased and the latency to evoke saccades increased as fixation neared the termination zone (a restricted region within craniotopic space) both before and after either lesion. Ablation of the SC, but not of the FEF, eliminated the saccadic inhibition to visual targets which resulted when the DMFC was stimulated in the intact animal. The findings suggest that additional channels besides those coursing through the FEF and SC are utilized by the DMFC to access the saccade generator in the brainstem.