Mirror visual feedback can induce motor learning in patients with callosal disconnection.

Mirror therapy using mirror visual feedback (MVF) has been applied to the stroke rehabilitation of hemiparesis. One possible mechanism of mirror therapy is the functional interhemispheric connectivity between sensorimotor areas via corpus callosum. To test this hypothesis, we investigated the MVF-induced motor learning in 2 patients with callosal disconnection. Callosal connection in patients was evaluated by clinical measures and the interhemispheric inhibition (IHI) using transcranial magnetic stimulation. Both patients suffered from somatosensory cognitive disconnection, and one showed the loss of IHI. Motor training with MVF significantly improved the motor behavior of both patients. Extending our previous study, the results of callosal patients suggested that the visual feedback through a mirror might play the crucial important role for the improvement of motor performance, rather than interhemispheric interaction via corpus callosum.