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Lior Shmuelof, Uri Hertz, Ehud Zohary; Mirror-like representation of observed actions. Journal of Vision 2008;8(6):829. doi: 10.1167/8.6.829.
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© ARVO (1962-2015); The Authors (2016-present)
The anterior intraparietal cortex (aIPS) is known to be involved in visually guided grasping. This region is also active when observing grasping movements. Here we investigate whether the viewpoint of the observer affects aIPS activation, as well as the speed of action imitation. Ten subjects observed video clips of the right or left hand making object grasping movements. In one set of clips the hand was shown from an egocentric point of view (i.e. the observed actions are similar to those seen when one performs them). In the other set, the clips were shown from an allocentric point of view (as one would see when observing his own actions in the mirror). The results indicate that the fMRI activation in the aIPS shows a contralateral preference for the observed hand when seen from an egocentric point of view (i.e. the right aIPS is significantly more active during observation of left hand clips than right hand clips. In the left aIPS, the preference was the opposite). Interestingly, for the allocentric point of view, the ipsilateral hand is favored. Subsequently, we looked for the behavioral correlates of this mirror-like cortical representation: Subjects observed sequences of finger tapping movements made by either the right or left hand from an egocentric or an allocentric point of view and had to imitate them as fast as possible with their right hand. Imitation of the right egocentric and left allocentric clips was significantly faster than imitation of the left egocentric and right allocentric clips, mirroring the patterns of activation in the aIPS. Additionally, egocentrically viewed actions were imitated faster than allocentric ones. The two experiments demonstrate a mirror-like representation of actions, which may stem from the inherent spatial compatibility that exists between our actions and their reflection in the mirror.
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