PRESACCADIC OMNIDIRECTIONAL BURST ACTIVITY IN THE BASAL INTERSTITIAL NUCLEUS IN THE MONKEY CEREBELLUM

We recorded saccade-related neurons in the vicinity of the dentate nuc leus of the cerebellum in two monkeys trained to perform visually guid ed saccades and memory-guided saccades. Among 76 saccade-related neuro ns, 38 showed presaccadic bursts in all directions. More than 80% of s uch burst neurons were located in the area ventral to, not inside, the dentate nucleus, which corresponded to the basal interstitial nucleus (BIN as previously described). We found that the activity of the BIN neurons was correlated with saccade duration but not with saccade ampl itude or velocity. Thus, when tested with visually guided saccades, th e burst started about 16 ms before saccade onset and ended about 33 ms before saccade offset, regardless of saccade amplitude. The character istic timing of the BIN cell activity was maintained for different typ es of saccades (visually guided, memory-guided and spontaneous saccade s), which had different dynamics. Although the number of spikes in a b urst for each neuron was linearly correlated with saccade amplitude fo r a given type of saccade, the slope varied depending on the type of s accade. Peak burst frequency was uncorrelated with saccadic peak veloc ity. In contrast, burst duration was highly correlated with saccade du ration regardless of the type of saccade. These results suggest that B IN neurons may carry information to determine the timing of saccades.