Twenty right-handed normal subjects performed an implicit visuomotor learning task with their non-dominant hand. The task (鈥渃ircuit game鈥? consisted in learning to navigate a pointer along a circuit as quickly and accurately as possible using a fMRI-compatible mouse. Velocity, accuracy, and performance indexes were used to characterise the motor learning pattern (shift/fit) and to perform fMRI correlation analysis in order to find the neural substrate associated with the shift and fit patterns during early motor skill learning.
Nine subjects showed a fit pattern (fitters), and eleven, a shift pattern (鈥渟hifters鈥?. fMRI analyses at whole group level (ANOVA) and at sub-group level demonstrated that the supplementary motor area (SMA) was more activated in 鈥渟hifters鈥?than in the 鈥渇itters鈥?groups and that the BOLD activation within the SMA correlated significantly with the on-line shift of the speed/accuracy trade-off in the 鈥渟hifters鈥?group.
Despite identical instructions and experimental conditions, during the first stage of motor skill learning normal subjects spontaneously adopted different patterns that can be differentiated based on distinct fMRI activation patterns. In this implicit visuomotor task, the SMA proper was the key area underlying the achievement of early successful motor skill learning, i.e. on-line shift of the speed/accuracy trade-off.