Differential motor cortex excitability during observation of normal and abnormal goal-directed movement patterns

Beta (similar to 20-Hz) activity induced by median nerve stimulation has been reported to be located in the primary motor cortex (M1) and associated with various movement-related tasks. It has been evident that the similar to 20-Hz activity was suppressed more in the observation of goal-directed than non-goal-directed tool use. However, it remains unclear whether this rhythmic activity is further modulated by the observation of normal and abnormal goal-directed hand movements. We recorded neuromagnetic responses in 19 right-handed healthy adults while they kept relaxed (Rest), manipulated a small cube (Act), observed videotapes with normal (Normal) or abnormal (Abnormal) hand actions. The M1 similar to 20-Hz rebound powers were quantified through minimum norm estimate and time-frequency analysis at the source level. The results showed that compared to the Rest condition, the M1 similar to 20-Hz activities were significantly decreased when subjects observed normal and abnormal hand actions. The suppression was more profound in the Normal than Abnormal condition, indicating a stronger M1 activation during observing graceful, undistorted movement patterns. Our data provided a neurophysiological basis to differentiate the motor cortical activities in the observation of normal and abnormal hand actions. Further research is warranted to verify its clinical benefits in patients with stroke. (C) 2017 Elsevier Ireland Ltd and Japan Neuroscience Society. All rights reserved.