PREFERENTIAL ACTIVITY OF DENTATE NEURONS DURING LIMB MOVEMENTS GUIDEDBY VISION

1. We recorded the activity of dentate neurons while monkeys (n = 2) p erformed sequential pointing movements under two task conditions: visu ally guided and remembered. For both conditions, a monkey faced a pane l with five touch pads. The animal began a trial by placing his right hand on a hold key in front of him. In the Remembered Sequence Task, l ight-emitting diodes (LEDs) over three touch pads were illuminated in a sequence as an instruction to the monkey. At the end of a variable i nstruction period, an auditory ''Go'' signal told the monkey to releas e the hold key and press the touch pads according to the instructed se quence. In the Tracking Task, the monkey was required to press three t ouch pads immediately after the LED over each of them was illuminated. 2. We recorded from 172 neurons in the dentate that showed task-relat ed changes in activity during the reaction time (RT) period (i.e., the interval between the onset of the Go signal and the release of the ho ld key). Approximately 40% of these neurons were considered task-depen dent because they displayed exclusive or enhanced (>+/-50%) changes in peak activity during the RT period for one of the two task conditions . Almost 80% of the task-dependent neurons displayed exclusive or enha nced activity changes during the Tracking Task. Many of these neurons were located ventral and lateral to dentate neurons, which were not ta sk-dependent. 3. These results suggest that a portion of the dentate n ucleus is preferentially involved in the generation and/or guidance of movement based on visual cues. Thus our observations provide further support for the concept that the cerebellum is not simply concerned wi th regulating movement parameters but also is involved in the control of higher order aspects of skeletomotor behavior.