Imagining movement of affected limbs aids stroke rehabilitation

Imagining movement of arms and legs that have been weakened from stroke may facilitate functional recovery of affected limbs, a Northwestern University study has found.

The effects of stroke vary, based on the type of stroke and its severity and location in the brain. The majority of strokes affect one of the brain’s hemispheres, resulting in muscle weakness or paralysis on the opposite side of the body — a condition known as hemiparesis.

Jennifer A. Stevens and co-researchers at the Feinberg School of Medicine and the Rehabilitation Institute of Chicago used a motor imagery training program for patients with hemiparesis, consisting of imagined wrist movements and mental simulations of reaching and object manipulation making use of a mirror-box apparatus.

An article describing their study appeared in a recent issue of Archives of Physical Medicine and Rehabilitation. The intervention targets the cognitive level of action processing, while its effects may be realized in overt behavioral performance, said Stevens, research assistant professor of physical medicine and rehabilitation at the Feinberg School.

“Actions generated using motor imagery adhere to the same movement rules and constraints that physical movements follow, and the neural network involved in motor imagery and motor execution overlap in areas of the brain concerned with movement,” said Stevens. The program consisted of three one-hour sessions for four consecutive weeks. The first task was computer-facilitated motor imagery training, during which time the participant was instructed to explicitly imagine his/her own hand completing a movement just observed on a computer screen.

For the second task, simulating, for example, the left arm moving, the investigators had the participant move the right arm around in the mirror-box workspace, resulting in a reflection of the affected left limb moving about successfully in space. Participants were instructed to “imagine the reflected limb actually is your limb moving about.”

Results showed that performance of the affected limb improved after the imagery intervention, indicated by increases in assessment scores and functionality and decreases in movement times.

Stevens and colleagues found that the greatest increases in function generally occurred during the month of intervention, suggesting that the behavioral effects were associated with the actual practice of mental simulation. It also is possible that motor simulation therapy in early stages of recovery — that is, less than six months — may increase the degree of this effect, Stevens said.