Binding personal and peripersonal space: Evidence from tactile extinction

Behavioral and neurophysiological studies suggest that the brain constructs different representations of space. Among these representations are person al and peripersonal space. Personal space refers to the space occupied by o ur bodies. Peripersonal space refers to the space surrounding our bodies, w hich can be reached by our limbs. How these two representations are bound t o give a unified sense of space in which humans act is not clear. We tested 10 patients with tactile extinction to investigate this issue. Tactile ext inction is an attentional disorder in which patients are unaware of being t ouched on their contralesional limb if they are also touched simultaneously on their ipsilesional limb. We hypothesized that mechanisms that bind pers onal and peripersonal representations would improve these patients' awarene ss of being touched on their contralesional limbs. Visual-tactile integrati on and intentional movements were considered candidate mechanisms. Patients were more likely to be aware of contralesional touch when looking towards their contralesional limb than when looking towards their ipsilesional limb , and when actively moving on tactile probes than when receiving tactile st imuli passively. The improved awareness of being touched on the contralesio nal limb under these conditions suggests that cross-sensory and sensorimoto r integration help bind personal and peripersonal space.