Lateralization of motor imagery following stroke.

OBJECTIVE: Motor imagery may activate the primary motor cortex (M1) and promote functional recovery following stroke. We investigated whether the hemisphere affected by stroke affects performance and M1 activity during motor imagery. METHODS: Twelve stroke patients (6 left, 6 right hemisphere) and eight healthy age-matched adults participated. Experiment 1 assessed the speed and ease of actual and imagined motor performance. Experiment 2 measured corticomotor excitability during imagined movement of each hand separately, and both hands together, using transcranial magnetic stimulation. RESULTS: For control participants, imagined movements were performed more slowly than actual movements, and right-hand MEPs were facilitated when they imagined moving their right hand or both hands together. Patients reported being able to imagine movements with either hand, despite no measurable facilitation of MEPs in the stroke-affected hand. In left hemisphere patients, MEPs were facilitated in the left hand during imagery of the right hand and both hands together. In right hemisphere patients, motor imagery did not facilitate MEPs in either hand. CONCLUSIONS: Motor imagery does not appear to facilitate the ipsilesional M1 following stroke. SIGNIFICANCE: Motor imagery may play a role in rehabilitating movement planning, but its role in directly facilitating corticomotor output appears limited.