Motor familiarity: brain activation when watching kinematic displays of one's own movements.

The perception of action is influenced by the observer's familiarity with its movement. However, how does motor familiarity with own movement patterns modulate the visual perception of action effects? Cortical activation was examined with fMRI while 20 observers were watching videotaped point-light displays of markers on the shoulders, the right elbow, and wrist of an opposing table tennis player. The racket and ball were not displayed. Participants were asked to predict the invisible effect of the stroke, that is, the ball flight direction. Different table tennis models were used without the observers knowing and being informed in advance that some of the presented videos displayed their own movements from earlier training sessions. Prediction had to be made irrespective of the identity of the player represented by the four moving markers. Results showed that participants performed better when observing their "own" strokes. Using a region-of-interest approach, fMRI data showed that observing own videos was accompanied by stronger activation (compared to other videos) in the left angular gyrus of the inferior parietal lobe and the anterior rostral medial frontal cortex. Other videos elicited stronger activation than own videos in the left intraparietal sulcus and right supramarginal gyrus. We suggest that during action observation of motorically familiar movements, the compatibility between the observed action and the observers' motor representation is already coded in the parietal angular gyrus--in addition to the paracingulate gyrus. The activation in angular gyrus is presumably part of an action-specific effect retrieval that accompanies actor-specific prefrontal processing. The intraparietal sulcus seems to be sensitive to incongruence between observed kinematics and internal model representations, and this also influences processing in the supramarginal gyrus.