Cerebral cortical activity associated with the orientation of visual attention in the rhesus monkey

Attentional mechanisms in the posterior parietal cortex and the frontal eye fields have been studied in the rhesus monkey. In each of these areas single neurons discharge in response to visual stimuli and the discharge is enhanced when the monkey makes a saccade to the stimulus. In the posterior parietal cortex this enhancement also occurs whenever the monkey attends to the target, regardless of the movement or nonmovement that the monkey might make. Conversely, neurons in the frontal eye fields give enhanced responses only before saccades, and some discharge before purposive saccades made to remembered targets, with no overt current visual guidance. Some cells in the frontal eye fields also anticipate the onset of predictable saccades.