Beyond the window: multisensory representation of peripersonal space across a transparent barrier.

A large body of neuropsychological evidence has been recently provided showing that humans can code visual objects in nearby space through multisensory visuo-tactile integrative processes, which share several similarities with the functional properties of bimodal neurons documented in neurophysiological studies. In particular, the phenomenon of visuo-tactile extinction reveals that crossmodal integration may take place in a privileged manner within a limited sector of space closely surrounding the body surface, i.e. in the near peripersonal space. Here we report that visuo-tactile extinction can seemingly be obtained when a physical, transparent barrier is interposed between the patients' hand and a proximal visual stimulus. These findings show that visuo-tactile representation of peripersonal space can be formed despite the subject's explicit awareness concerning the physical impossibility for the hand to be touched. This phenomenon indicates that multisensory integrative processing can occur in a bottom-up fashion without necessarily being modulated by more 'cognitive' processes. Such integration may be functionally important for automatic reactions such as head turning or hand withdrawal.