Our ability to interact with the environment requires the integration of multisensory information for the construction of spatial representations. The peripersonal space (i.e., the sector of space closely surrounding one's body) and the integrative processes between visual and tactile inputs originating from this sector of space have been at the center of recent years investigations. Neurophysiological studies provided evidence for the presence in the monkey brain of bimodal neurons, which are activated by tactile as well as visual information delivered near to a specific body part (e.g., the hand). Neuropsychological studies on right brain-damaged patients who present extinction and functional neuroimaging findings suggest the presence of similar bimodal systems in the human brain. Studies on the effects of tool-use on visual-tactile interaction revealed similar dynamic properties of the peripersonal space in monkeys and humans. The functional role of the multisensory coding of peripersonal space is, in our hypothesis, that of providing the brain with a sensori-motor interface for body-objects interactions. Thus, not only it could be involved in driving involuntary defensive movements in response to objects approaching the body, but could be also dynamically maintained and updated as a function of manual voluntary actions performed towards objects in the reaching space. We tested the hypothesis of an involvement of peripersonal space in executing both voluntary and defensive actions. To these aims, we joined a well known cross-modal congruency effect between visual and tactile information to a kinematic approach to demonstrate that voluntary grasping actions induce an on-line re-weighting of multisensory interactions in the peripersonal space. We additionally show that this modulation is handcentred. We also used a motor evoked potentials approach to investigate which coordinates system is used to code the peripersonal space during motor preparation if real objects rapidly approach the body. Our findings provide direct evidence for automatic hand-centred coding of visual space and suggest that peripersonal space may also serve to represent rapidly 3 approaching and potentially noxious objects, thus enabling the rapid selection of appropriate motor responses. These results clearly show that peripersonal space is a multisensori-motor interface that might have been selected through evolution for optimising the interactions between the body and the objects in the external world.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00675247 |
| Date | 20 November 2009 |
| Creators | Brozzoli, Claudio |
| Publisher | Université Claude Bernard - Lyon I |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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