Activity of primate V1 neurons during the gap saccade task.

When a saccadic eye movement is made toward a visual stimulus, the variability in accompanying primary visual cortex (V1) activity is related to saccade latency in both humans and simians. To understand the nature of this relationship, we examined the functional link between V1 activity and the initiation of visually guided saccades during the gap saccade task, in which a brief temporal gap is inserted between the turning off of a fixation stimulus and the appearance of a saccadic target. The insertion of such a gap robustly reduces saccade latency and facilitates the occurrence of extremely short-latency (express) saccades. Here we recorded single-cell activity from macaque V1 while monkeys performed the gap saccade task. In parallel with the gap effect on saccade latency the neural latency (time of first spike) of V1 response elicited by the saccade target became shorter, and the firing rate increased as the gap duration increased. Similarly, neural latency was shorter and firing rate was higher before express saccades relative to regular-latency saccades. In addition to these posttarget changes, the level of spontaneous spike activity during the pretarget period was negatively correlated with both neural and saccade latencies. These results demonstrate that V1 activity correlates with the gap effect and indicate that trial-to-trial variability in the state of V1 accompanies the variability of neural and behavioral latencies.