Different brain correlates for watching real and virtual hand actions

We investigated whether observation of actions reproduced in three-dimensio nal virtual reality would engage perceptual and visuomotor brain processes different from those induced by the observation of real hand actions. Parti cipants were asked to passively observe grasping actions of geometrical obj ects made by a real hand or by hand reconstructions of different quality in 3D virtual reality as well as on a 2D TV screen. We found that only real a ctions in natural environment activated a visuospatial network including th e right posterior parietal cortex. Observation of virtual-reality hand acti ons engaged prevalent visual perceptual processes within lateral and mesial occipital regions. Thus, only perception of actions in reality maps onto e xisting action representations, whereas virtual-reality conditions do not a ccess the full motor knowledge available to the central nervous system. (C) 2001 Academic Press.