Prefrontal unit activity during a delayed oculomotor task in the monkey.

1. Unit activity was recorded in the prefrontal cortex of Rhesus monkeys during performance of a delay task with two motor components, an ocular saccade and an arm movement, following a complex pattern of auditory and visual stimuli. A special feature of the paradigm was that onsets of the different sensory stimuli, orienting saccade and arm movement were dissociated in time at predetermined time intervals. 216 task-related units were recorded. Discussion of the data focuses on two groups of cells the activity of which is modified by the saccade: the signal-related pre-saccadic tonic cells and the post-saccadic tonic cells. 2. Activity of signal-related pre-saccadic tonic cells was initiated with the onset of peripheral stimuli, visual and/or auditory, and terminated with an orienting saccade. Spatial selectivity was a feature of most units. They seemed to encode the region of space cued by the stimulus. 3. Many units were visually responsive. Activation of these depended both upon retinal locus of the stimulus and the requirement they imposed on subsequent behavior. Termination of their activity demanded foveation of some visual targets, not necessarily the one which had initiated their response. 4. The majority of these signal-related pre-saccadic tonic cells responded to onset of auditory stimuli. The termination of tonic activity in these cells with foveation of the region in space from which the signal originated suggests a spatial memory process that is no longer used when the visual fixation response can signal equivalent spatial information.(ABSTRACT TRUNCATED AT 250 WORDS)