Audio-tactile multisensory integration as a proxy for full body peri-personal space

Peri-personal space (PPS) — i.e., the space immediately surrounding the body — has been traditionally conceived as the space reachable through limb movements, and therefore, it remained centered on a specific peripheral extremity (most prominently, the hand and the face). However, we do experience our body in its space as a whole and not only as a discrete addition of body parts, thus begetting the question: Is there a full body representation of PPS? And if so, what are its characteristics and boundaries? In a first set of experiments, through the use of a novel audio-tactile paradigm, we (i) established the presence of a full body PPS, (ii) determined its boundary both in the front and backspace, and (iii) compared its spatial extent to the one of the peri-hand space. In addition, we observed a meshing between peri-trunk and peri-hand space when these two are in close physical proximity, and established a direct relationship, as it’s prominently shown in monkey electrophysiology data, between the velocity of incoming stimuli and the expansion of PPS. Our findings argue for the possibility of utilizing an audio-tactile multisensory integration paradigm in order to measure full body PPS, as well as establish the aforementioned space characteristics. We show analogous results to those observed in electrophysiology data, as well as expand on previous literature by showing an interplay between different conceptions of PPS.