Shu WATANABE, Masahiro ABO, Yoshiaki KIKUCHI, Atsushi SENO,Hironobu KURUMA, Satoshi MIYANO, Kyozo YONEMOTO

Tokyo Metropolitan University of Health Sciences

(Received 14 May 2004; accepted 11 June 2004)

Abstract: In order to clarify the influence of an external cue (paced sound) on the activation of the presupplementary motor area (pre-SMA) and supplementary motor area (SMA proper), we scanned 10 right-handed healthy subjects by functional MRI while they performed (1) self-initiated finger-to-thumb opposition movements on once every 1 sec, and (2) externally triggered the same movements using a metronome's paced sound. During self-initiated movements with the right hand, the right and left SMA proper were significantly activated in 6 and 3 out of 10 subjects, respectively. These activations were diminished or disappeared in 5 out of 6 and 2 out of 3 subjects during the paced sound trials. With the left hand, the right and left SMA proper were significantly activated in 5 and 1 out of 10 subjects respectively. During the externally paced sound trials, these activations were respectively diminished or disappeared in 4 out of 5 and 1 out of 1 subject. On the other hand, pre-SMA activation was minimal for either hand during the self-initiated task. These preliminary results are consistent with previous reports that the SMA proper plays an important role, especially in self-paced movements rather than externally triggered movements, which might explain the paradoxical movements in Parkinson's disease because the basal ganglia tightly connect with the supplementary motor area.

Key words: supplementary motor area, paradoxical movement, activation study