The influence of paced sound on activation of cerebellum in a finger opposition task: A fMRI study

Abstract

In the field of rehabilitation of patients with Parkinson's disease, external cues (visual or auditory information) are important in execution of activities of daily living, which is called "paradoxical movement". However, the neural mechanism of paradoxical movement is unclear. In order to clarify the influence of external cues (paced sound) on the activation of the cerebellum, we scanned 9 right-handed healthy subjects by functional MRI while they performed (1) self-initiated finger-to-thumb opposition movements once every second, and (2) the same movements externally triggered by a metronome's sound. During self-initiated movements with the right hand, the cerebellum was activated in all subjects. During externally triggered movements, the activation was decreased in 7 of 9 subjects, and vanished in 1 of 9 subjects. During self-initiated movements with the left hand, the cerebellum was activated in 8 of 9 subjects. During externally triggered movements, the activation was decreased in 6 of 8 and vanished in 1 of 8 subjects. These results suggest the cerebellum's role is feed-forward control during self-initiated movements, but external cues take the place of feed-forward control during externally triggered movements.