Abstract
During rehabilitation for Parkinson's disease, physical therapists often utilize visual or auditory guidance to facilitate movement in patients. However, the neural mechanism involved in these procedures is unclear. Goldberg (1985) proposed an internal and external loop of motor control that is supported by much physiological evidence from primate research. However, brain imaging studies are insufficient to verify this hypothesis. In this study, we scanned eleven right-handed healthy subjects by functional magnetic resonance imaging while they performed (1) self-initiated finger-to-thumb opposition movements once every second and (2) identical movements externally triggered by the sound of a metronome. With the externally triggered movements, activation of the cerebellum and temporal gyrus was observed to decrease, and that of the premotor cortex and parietal cortex was observed to increase. We concluded that the cerebellum and supplementary motor area constitute a part of the internal loop, while the premotor cortex and parietal cortex are involved in the external loop.
