The walking after stroke called hemiparetic gait is characterized by slow and asymmetrical steps with poor motor control on the paretic leg while paradoxically increasing the cost of energy expenditure. Biomechanical evidence shows that impaired gait performance for people with chronic stroke is not solely the result of the loss of muscle strength, but involves complicated movement discoordination across multiple joints in the affected leg. This has been taken to indicate a persistent motor control deficit in the paretic leg post stroke. Recent imaging studies suggest that the persistent motor control deficit after stroke may be the result of the disruption of motor memory consolidation, a process by which a newly-learned motor skill is transformed from a fragile state to a stable state and is saved in our brain afterward. This indicates that the same brain area responsible for controlling motor activity is also involved in memorizing newly-learned skills during the early stage of motor learning. Presence of persistent motor control deficits in the chronic stage may be attributed to the fact that damage to the brain cortex significantly impacts the ability of acquiring motor skills and consequentially defers the improvement of motor function, including gait.
Stroke survivors frequently show persistent gait deficits in their chronic stages even after years of intensive rehabilitation. This may be caused by diminished capability of re-acquiring motor skills post stroke. Thus, the overall purpose of this research project is to examine stroke survivors' capability of learning a novel leg task over 3 visits, 1-2 weeks apart. The capability of learning a new skill is then correlated with the individual's neurological functions (nerve activity and movement coordination) and her/his gait performance (gait speed, gait symmetry, and force production).