Predictive signals in the pursuit area of the monkey frontal eye fields.
In order to pursue a moving target with our eyes, visual motion-signals are converted into eye movement commands. Because of delays in processing visual information, prediction is necessary to compensate for those response-delays and maintain target images on the foveae. Previous studies showed that the majority of FEF pursuit neurons receive visual signals related to actual and predicted target motion. However, in those studies, discharge related to the memory of visual motion could not be separated from that related to prediction. To distinguish the two, while fixating a stationary spot, monkeys were required to memorize the direction of random dot motion (cue-1). After a delay (delay-1), a second cue (cue-2) instructed the monkeys to prepare either pursuit in the memorized direction or to maintain fixation. After a second delay (delay-2), the monkeys selected the correct response. In virtually all tested neurons that showed a visual motion-response to cue-1, the response was not maintained during the delay-1. The majority of responsive neurons were modulated during cue-2 and delay-2. Changing the delay-2 duration also changed the duration of discharge modulation, suggesting that delay-2 modulation was predictive. These results suggest that activity related to visual motion-memory was not conveyed by the discharge of caudal FEF pursuit neurons.