Responses of primate dentate neurons to different trajectories of the limb.

The activity of neurons in the dentate nucleus of the squirrel monkey was studied during the execution of a controlled, sequential movement that required different trajectories of the forearm. Examination of 207 dentate neurons ipsilateral to the performing limb revealed that over 80% of the neurons isolated were distinctly correlated with performance. The majority of these neurons had a tonic discharge pattern that usually increased coincident with the start of the movement and was maintained throughout most of the performance. A smaller group of cells ahd a burst of activity that was restricted only to a narrow part of the performance. About 30% of the tonic neurons altered their pattern of discharge whenever different limb trajectories were required, but burst cells showed exxentially no change. Detailed analysis of spike patterns revealed that no dentate neurons were phasically correlated with individual flexion-extension cycles of the performance sequence. Dentate neurons appear to be related to some general function of motor performance rather than the actions of joints or muscles used to execute the task.