Interference of grasping observation during prehension, a behavioural study

During the last 10 years a considerable number of neurophysiological and functional imaging studies have provided evidence that observation and execution of movements activate common representations. Furthermore, several behavioural studies suggest that action observation can influence the performance of movements. Recently it was shown that viewing incongruent movements interferes with the execution of non-object oriented sinusoidal arm movements (Kil-ner et al. in Curr Biol 13:522-525, 2003). In the current study, we investigated whether interference of action observation also occurs during goal-directed prehension movements. Participants were required to grasp cubes of different sizes while simultaneously observing an actor performing grasping or pointing movements. The actors' movement could be directed at objects that were identical, or different in size to the cube grasped by the participant. The results showed that maximum grip aperture was affected by observation of grasping towards larger objects. No effect of object size was found during observation of pointing movements. These results suggest that observation of grasping movements can interfere with the on-line control of prehension movements and provides further evidence for overlapping networks for grasping observation and execution.