Localized high gamma motor oscillations respond to perceived biologic motion.

Power changes in the beta frequency range (17-25 Hz) in the human motor and premotor areas during action observation have been associated with the mirror neuron system and have been studied extensively. These changes mimic motor activity during actual motion execution, albeit reduced in strength. Recent noninvasive (EEG/magnetoencephalography) and invasive studies (electrocorticography) have shown that during actual motion, beta power changes are accompanied by highly localized changes in the high gamma band (70-100 Hz). In this study, we investigate, using 27-channel EEG in combination with a generic head model and a cortical mapping algorithm, whether such high gamma changes are also present during motion observation. Subjects were presented with a 2.7-second video of a moving hand, contrasted with a video of moving scenery of equal length. Our results show nonlateralized beta band decrease in power in response to the moving hand versus the response to the moving scenery. We also find significant increase in high gamma power. However, unlike the beta band response, increases in this band are lateralized, with a preference for the hemisphere of the dominant hand.