Relationships between sensory input, motor output and unit activity in interpositus and red nuclei during intentional movement.

The relationship between unit activity in interpositus (8 units) and red nuclei (11 units) and the EMG activity of the biceps during intentional elbow flexion movements was investigated by means of cross-correlation analysis. This analysis showed that there were long-lasting (200 msec) changes in the probability of EMG activity both before and after a single spike in neurons which covaried with the motor output. The dependence of the activity of these units on sensory inputs was investigated by (1) calculating the quantitative relationship between angular displacement and unit activity and (2) recording unit activity after the sensory input from peripheral afferents had been eliminated by dorsal rhizotomy.