Delay activity of saccade-related neurons in the caudal dentate nucleus

21 The caudal dentate nucleus (DN) in lateral cerebellum is connected with two 22 visual/oculomotor areas of the cerebrum, the frontal eye field (FEF) and lateral 23 intraparietal (LIP) cortex. Many neurons in FEF and LIP produce “delay activity” 24 between stimulus and response that correlates with processes such as motor planning. 25 Our hypothesis was that caudal DN neurons would have prominent delay activity as well. 26 From lesion studies, we predicted that this activity would be related to self-timing, i.e. the 27 triggering of saccades based on the internal monitoring of time. We recorded from 28 neurons in the caudal DN of monkeys (Macaca mulatta) that made delayed saccades with 29 or without a self-timing requirement. Most (84%) of the caudal DN neurons had delay 30 activity. These neurons conveyed at least three types of information. First, their activity 31 was often correlated, trial-by-trial, with saccade initiation. Correlations were found more 32 frequently in a task that required self-timing of saccades (53% of neurons) than in a task 33 that did not (27% of neurons). Second, the delay activity was often tuned for saccade 34 direction (in 65% of neurons). This tuning emerged continuously during a trial. Third, the 35 time course of delay activity associated with self-timed saccades differed significantly 36 from that associated with visually-guided saccades (in 71% of neurons). A minority of 37 neurons had sensory-related activity. None had presaccadic bursts, in contrast to DN 38 neurons recorded more rostrally. We conclude that caudal DN neurons convey saccade39 related delay activity that may contribute to the motor preparation of when and where to 40 move. 41 42