Forearm oscillation during cooling of the dentate mucleus in the monkey.

A study was made of oscillations in arm acceleration in monkeys performing a self-paced manual step-tracking task. Power spectral density analyses of segments of arm acceleration data from normal monkeys containing both flexion and extension movements and intermovement holding periods showed three major peaks at 1-1.5 Hz, 3-5 Hz and 5-7 Hz. Cooling of the dentate nucleus produced a marked increase in the relative magnitude of the 3-5 Hz spectral band. The spectral peak in this frequency range was larger than the other two which were also present during cooling. Autocorrelation functions from long segments of data containing flexion and extension movements and intermovement holding periods showed regular periodic variations in both normal and cooled animals. This suggests that the ongoing oscillations were not changed in phase by the occurrence of the self-initiated arm movements.