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 V1 activity is related to saccade latency in both human (Bompas et al., 2015) and non-human (Lee et al., 2010) primates. In order 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 interposed 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 (Saslow, 1967), and facilitates the occurrence of extremely short latency (express) saccades (Fischer and Boch, 1983). 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 post-target changes, the level of spontaneous spike activity during the pre-target period was negatively correlated with both neural and saccade latencies. These results demonstrate that V1 activity correlates with the gap effect, and indicate that the trial-to-trial variability in the state of V1 underlies the variability of neural and behavioral latencies.

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