Functional cerebral reorganization following motor sequence learning through mental practice with motor imagery.

The goal of the present study was to examine, via positron emission tomography, the functional changes associated with the learning of a sequence of foot movements through mental practice with motor imagery (MI). Following intensive MI training over several days, which led to a modest but significant improvement in performance, healthy subjects showed an increase in activity restricted to the medial aspect of the orbitofrontal cortex (OFC), and a decrease in the cerebellum. These main results are largely consistent with those found in a previous study of sequence learning performed in our laboratory after physical practice of the same task [NeuroImage 16 (2002) 142]. Further analyses showed a positive correlation between the blood flow increase in the OFC and the percentage of improvement on the foot sequence task. Moreover, the increased involvement of the medial OFC revealed a modality specific anatomo-functional organization, as imagination of the sequential task after MI practice activated a more posterior region than its execution. These results demonstrate that learning a sequential motor task through motor imagery practice produces cerebral functional changes similar to those observed after physical practice of the same task. Moreover, the findings are in accord with the hypothesis that mental practice with MI, at least initially, improves performance by acting on the preparation and anticipation of movements rather than on execution per se.