Visual influences on sensorimotor EEG responses during observation of hand actions.

There is growing interest within the field of social-cognitive neuroscience in the dynamics of sensorimotor EEG rhythms during the observation of actions performed by others. However, there remain important gaps in the literature regarding the effects of perceptual aspects of the observed hand movements. This study investigated two visual influences on the EEG response to hand actions. Specifically, the perspective of the action in relation to the participant (egocentric/allocentric) was varied and the effect of the hand used to carry out the action (left/right) was also assessed. While EEG was recorded, 28 undergraduate participants observed video clips showing an actor's hand reaching for, grasping, and lifting a cylindrical object across four conditions (right-hand egocentric, left-hand egocentric, right-hand allocentric, and left-hand allocentric). For actions viewed from an egocentric perspective, significantly greater event-related desynchronization (ERD) was present in the 7-9 Hz range over right mid-frontal, right central, and bilateral mid-parietal sites for right-handed actions compared to left-handed actions. In addition, greater ERD was observed within the 7-9 Hz band during the observation of right-handed egocentric actions compared to actions viewed from the allocentric perspective. This finding was present at bilateral central and mid-parietal sites, and emerged as an anticipatory effect prior to the onset of the observed hand movements.