Evidence for a functional subdivision of Premotor Ear-Eye Field (Area 8B)

The Supplementary Eye Field (SEF) and the Frontal Eye Field (FEF) have been described asparticipating in gaze shift control. Recent evidence suggests, however, that other areas of the dorsomedialprefrontal cortex also influence gaze shift. Herein, we have investigated electrically evoked ear- and eyemovements from the Premotor Ear-Eye Field, or PEEF (area 8B) of macaque monkeys. We stimulated PEEFduring spontaneous condition (outside the task performance) and during the execution of a visual fixationtask (VFT). In the first case, we functionally identified two regions within the PEEF: a core and a belt. In thecore region, stimulation elicited forward ear movements; regarding the evoked eye movements, in somepenetrations, stimulation elicited contraversive fixed-vectors with a mean amplitude of 5.14°; while in otherpenetrations, we observed prevalently contralateral goal-directed eye movements having end-points that fellwithin 15° in respect to the primary eye position. On the contrary, in the belt region, stimulation elicitedbackward ear movements; regarding the eye movements, in some penetrations stimulation elicitedprevalently contralateral goal-directed eye movements having end-points that fell within 15° in respect to theprimary eye position, while in the lateral edge of the investigated region, stimulation elicited contralateralgoal-directed eye movements having end-points that fell beyond 15° in respect to the primary eye position.Stimulation during VFT either did not elicit eye movements or evoked saccades of only a few degrees.Finally, even though no head rotation movements were observed during the stimulation period, we viewed arelationship between the duration of stimulation and the neck forces exerted by the monkey’s head. Wepropose an updated vision of the PEEF composed of two functional regions, core and belt, which may beinvolved in integrating auditory and visual information important to the programming of gaze orientingmovements.