Facilitation of corticospinal excitability according to motor imagery and mirror therapy in healthy subjects and stroke patients

Objective To delineate the changes in corticospinal excitability when individuals are asked to exercise their hand using observation, motor imagery, voluntary exercise, and exercise with a mirror. Method The participants consisted of 30 healthy subjects and 30 stroke patients. In healthy subjects, the amplitudes and latencies of motor evoked potential (MEP) were obtained using seven conditions: (A) rest; (B) imagery; (C) observation and imagery of the hand activity of other individuals; (D) observation and imagery of own ipsilateral hand activity; (E) observation and imagery of the hand activity of another individual with a mirror; (F) observation and imagery of own symmetric ipsilateral hand activity (thumb abduction) with a mirror; and (G) observation and imagery of own asymmetric ipsilateral hand activity (little fi nger abduction) with a mirror. In stroke patients, MEPs were obtained in the A, C, D, E, F conditions. Results In both groups, increment of the percentage MEP amplitude (at rest) and latency decrement of MEPs were significantly higher during the observation of the activity of the hand of another individual with a mirror and during symmetric ipsilateral hand activity on their own hand with a mirror than they were without a mirror. In healthy subjects, the increment of percentage MEP amplitude and latency decrement were signifi cantly higher during the observation of the symmetric ipsilateral hand activity with a mirror compared to the observation of the activity of the asymmetric ipsilateral hand with a mirror of their own hand. Conclusion In both groups, corticospinal excitability was facilitated by viewing the mirror image of the activity of the ipsilateral hand. Th ese fi ndings provide neurophysiological evidence supporting the application of various mirror imagery programs during stroke rehabilitation.