Cortical organization of sensory corrections in visuomotor skill acquisition.

During sensorimotor skill acquisition, early learning of the required neuromuscular pattern and sensorimotor mappings is followed by an intermediate stage of gradually increasing consistency and efficiency of execution, which gives way, with persistent practice, to the later stages of automatization. It has been suggested that the intermediate stage is distinguished by refinements in the background sensory corrections that support, stabilize and smoothen the fine motor adjustments required by the new coordination. While the later stages of motor refinement are thought to be sub-cortically organized, the neurophysiology of the proposed sensory learning component in the intermediate stage is not well understood. During explicit learning of a visually cued finger-tap sequence, the present research used fMRI to isolate those cortical activations that were significant in the immediate post-learning phase, but were not also observed during the corresponding pre-learning phase. Such exclusively post-learning activation occurred significantly more in visual and somatosensory association areas, than in primary somatosensory or primary and secondary motor areas. These results show that the intermediate stage of skill acquisition has a significant sensory learning component, and that the process has observable cortical correlates.