Abstract
The receptive fields (RFs) of neurons in many areas of the primate visual system are altered immediately prior to the initiation of saccadic eye movements. However, the exact nature of those RF dynamics is unknown. Typically, the dynamic changes of RFs have been inferred on the basis of only a few visual stimulus positions rather than from detailed spatial profiles of presaccadic RFs. We measured detailed RF profiles of frontal eye field (FEF) neurons by probing a large number (> = 72) of stimulus positions within a large portion of visual space in the contralateral hemifield. RF profiles were obtained both during passive fixation (fixation trials) and immediately prior to the initiation of visually guided saccades (presaccadic trials). On both types of trials, we recorded the responses of FEF neurons to probe stimuli (1° × 1° white squares) briefly flashed (∼20 ms) at random positions. On fixation trials, multiple positions were probed in succession at 0.5 Hz and the monkey was rewarded for maintaining fixation throughout the trial. On each presaccadic trial, the monkey was rewarded for making a saccade to a visual target (0.5° × 0.5° red square) in the contralateral hemifield and a single position was probed within 100 ms of saccade initiation. Thus far, we find clear presaccadic changes in the RF profiles of FEF neurons. In particular, we observe that presaccadic RFs move toward the saccade endpoint in a direction nonparallel to the saccade vector.