Modifications of the interactions in the motor networks when a movement becomes automatic.

A crucial feature of the motor system is the ability to control some movements automatically. We have previously shown that all parts of the motor networks reduce their activity with automaticity, and, while this change may indicate increased efficiency in terms of neural processing, it is not clear how motor skill can be maintained after a reduction of neural activity. In the current study, we used functional MRI (fMRI) to investigate influences on the effective connectivity of the brain motor networks when movements become automatic. Subjects practiced a sequential movement until they could execute it automatically, and task-related brain fMRI activation was measured before and after they achieved automaticity. Using the psychophysiological interaction (PPI) method, we found that the cerebellum, cingulate motor area, supplementary motor area, and putamen had significantly greater connectivity, whereas the precuneus had less connectivity in the motor networks at the automatic stage. Our findings demonstrate that the importance of the attention networks decrease when movements become automatic. Moreover, the process of automaticity is accompanied by a strengthened interaction of central motor networks even though the magnitude of the activation is decreased. We speculate that this increase in connectivity reflects more efficient neural coding of movement at the automatic stage.