筋収縮の繰り返しが運動野の興奮性の変化に及ぼす影響

概要

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Studies of use-dependent plastic changes have recently focused on the primary motor cortex (Ml) in humans. In the present study, firstly, we investigated the use-dependent plasticity of the first dorsal interosseous (FBI) muscle after repetitive index finger abduction movements. Secondly, we investigated whether practice of different muscle contraction modes-isometric task and isoton ic task-was effective. The data obtained showed excitability changes of motor evoked potentials (MEPs) in the FBI muscle during motor imagery. The rapid plastic changes induced by the practice tasks in Ml were dependent on the effects of both forms of muscle contraction and their motor imagery. In particular, the finding that isometric and isotonic tasks had different degrees of effectiveness, i.e. the isotonic task was effective and the isometric task less effective, provided a foundation for understanding the processes involved in motor adaptation learning. Furthermore, the clarification of two different learning stages suggested that practice of the simple motor task induced excitability changes in Ml even within brief practice sessions, and revealed the existence of early and slow stages in motor learning. These results confirm the notion that distinct motor cortical regions could be associated with different stages of motor learning and performance. The neurophysiological mechanisms involved are discussed in more details.
2003-09-10