TRANSITION OF BRAIN ACTIVATION FROM FRONTAL TO PARIETAL AREAS IN VISUOMOTOR SEQUENCE LEARNING

We studied the neural correlates of visuomotor sequence learning using functional magnetic resonance imaging (fMRI). In the test condition, subjects learned, by trial and error, the correct order of pressing tw o buttons consecutively for 10 pairs of buttons (2 x 10 task); in the control condition, they pressed buttons in any order. Comparison betwe en the test condition and the control condition revealed four brain ar eas specifically related to learning: the dorsolateral prefrontal cort ex (DLPFC), the presupplementary motor area (pre-SMA), the precuneus, and the intraparietal sulcus (IPS). We found that the time course of a ctivation during learning was different between these areas. To normal ize the individual differences in the speed of learning, we classified the performance of each subject into three learning stages: early, in termediate, and advanced stages. Both the relative increase of signal intensity and the number of activated pixels within the four areas sho wed significant changes across the learning stages, with different tim e courses. The two frontal areas, DLPFC and pre-SMA, were activated in the earlier stages of learning, whereas the two parietal areas, precu neus and IFS, were activated in the later stages. Specifically, DLPFC, pre-SMA, precuneus, and IFS were most highly activated in the early s tage, in both the early and intermediate stages, in the intermediate s tage, and in both the intermediate and advanced stages, respectively. The results suggest that the acquisition of visuomotor sequences requi res frontal activation, whereas the retrieval of visuomotor sequences requires parietal activation, which might reflect the transition from the declarative stage to the procedural stage.