Automatic prediction error responses to hands with unexpected laterality: an electrophysiological study.

Little is known about how the human brain keeps track of body parts in the visual field. Here we show that unattended images of right/left hands elicit a mismatch response when they violate a regularity established by repeated visual presentations of the other hand. In a visual oddball experiment we found mismatch responses to hands with unexpected laterality (e.g. left versus predicted right hand) in the periphery of the visual field. Unexpected left hands were processed predominantly in the contralateral superior parietal cortex, whereas unexpected right hands evoked differential activity in the contralateral superior parietal, ventral premotor, prefrontal and temporal areas, indicating a more elaborate automatic processing of the dominant hand. The amplitude of the differential activity to the right hand correlated with handedness test scores. Our results reveal the continuous monitoring of the left or right identity of hands, which is prerequisite to the ability to automatically transform observed actions into the observer's ego-centric spatial reference frame.