Fig. 1.

Spontaneous movements are reduced after MPTP treatment. The monkey's spontaneous movements in its home cage were measured daily using two reflected sonar beams. Each session lasted 30 min, and each channel was sampled at 100 Hz. A,B, Examples of spontaneous movements of monkey H before and after MPTP treatment, respectively. C,D, SDs of sonar traces of monkeys H and I, respectively, before and after MPTP treatment. Marked areas represent the MPTP injection days (no recordings were performed during that time). ⋄ and asterisks represent horizontal and vertical sonar beams, respectively.