Motor learning after stroke: Is skill acquisition a prerequisite for contralesional neuroplastic change?

Abstract

Limited data directly characterize the dynamic evolution of brain activity associated with motor learning after stroke. The current study considered whether sequence-specific motor skill learning or increasing non-specific use of the hemiparetic upper extremity drive functional reorganization of the contralesional motor cortex after stroke. Eighteen individuals with chronic middle cerebral artery stroke practiced one of two novel motor tasks; a retention test occurred on a separate fifth day. Using the hemiparetic arm, participants performed a serial targeting task during two functional MRI scans (day one and retention). Participants were randomized into either a task-specific group, who completed three additional sessions of serial targeting practice, or a general arm use group, who underwent three training sessions of increased but non-task specific use of the hemiparetic arm. Both groups performed a repeated sequence of responses that may be learned, and random sequences of movement, which cannot be learned. Change in reaction and movement time for the repeated sequence indexed motor learning; shifts in the laterality index (LI) within primary motor cortex (M1) for repeated and random sequences illustrated training effects on brain activity. Task-specific practice of the repeated sequence facilitated motor learning and shifted the LI for M1 as shown by a reduced volume of contralesional cortical activity. Random sequence performance did not stimulate motor learning or alter the LI within the task-specific training group. Further, between-group comparisons showed that increasing general arm use did not induce motor learning or alter brain activity for either random or repeated sequences. Motor skill learning of a repeated sequence altered cortical activation by inducing a more normal, contralateral pattern of brain activation. Our data suggest that task-specific motor learning may be an important stimulant for neuroplastic change and can remediate maladaptive patterns of brain activity after stroke.