Action observation facilitates motor cortical activity in patients with stroke and hemiplegia

Motor imagery (MI) is a mental practice that reproduces the visual- and/or kinesthetic-modality brain activations accompanying movement. It is a useful rehabilitation technique as the affected motor cortex can be stimulated in patients with stroke and hemiplegia. However, most patients with stroke have difficulty with MI owing to advanced age and/or higher-cognitive dysfunction, thus impairing their ability to internally simulate the action. We therefore investigated whether action observation (AO), an alternative form of motor stimulation that works via the mirror-neuron system, could facilitate motor cortical activity in such patients. Combined AO and physical training of the observed actions has been reported to have a positive impact on motor deficits after stroke. Eleven patients with stroke and hemiplegia affecting the hand performed MI and AO with verbal and video instructions under 19 channels of electroencephalogram (EEG) recording. The event-related desynchronization (ERD) was measured as an electroencephalographic marker of motor cortical activity. The ERD power in the AO condition (30.0±5.0%) was significantly higher than that in the MI condition (12.2±3.9%). These results suggest that AO could be a good option for patients with stroke who have difficulty using MI to effectively stimulate and reestablish cortical-peripheral motor pathways.