Topographic distribution of fixation-related units in the dorsomedial frontal cortex of the rhesus monkey.

Most cells in the dorsomedial frontal cortex of the rhesus monkey had activity related to saccadic eye movement and/or visual fixation. This activity changed depending upon the position of a fixation target, which suggested coding for the target location in spatial coordinates. Further analysis of such activity revealed a topographical distribution of neurons: neurons in the rostral part of the area were more active with eyes to the contralateral position, while those in the caudal part were more active with eyes to the ipsilateral position; also, cells in the medial part of the area had higher activity with a downward fixation position, whereas those in the lateral part had higher activity with an upward fixation position. This distribution of units was in agreement with the map of termination zones of saccadic eye movements evoked by electrical stimulation of the same area. These observations provide evidence for the hypothesis that the dorsomedial frontal cortex is organized in spatial coordinates and is involved in specifying the position of visual fixation.