Involvement of human left frontoparietal cortices in neural processes associated with task-switching between two sequences of skilled finger movements.

In this study, we demonstrate the involvement of left frontoparietal cortices in neural processes for task-switching between skilled movements. Functional magnetic resonance imaging was conducted while thirty-two right-handed healthy participants performed two sequential finger-movement tasks with their left hands. One group (n = 16) trained these tasks through random-practice (tasks were either switched or repeated trial by trial) on one day and blocked-practice (successive intensive practice of each task) on the next day, while the remaining participants practiced in the reverse order. On the first day, performance of both tasks improved in all participants, suggesting that the two skilful tasks can be learned in both practice schedules. However, during the random-practice, the performance in the switched trials initially deteriorated and gradually approached to that in the repeated trials as the practice proceeded. The left (mainly inferior) frontoparietal cortices showed greater preparatory activity for the switched trials compared with the repeated trials in a left-hemispheric dominant manner, and the left intraparietal activity decreased as the performance of the switched trials improved. The results indicate that neural processes for task-switching are associated with the greater preparatory activity in the left inferior frontoparietal cortices, and the efficient switching may proceed concomitantly with the left intraparietal activity reduction.