Body part-centered and full body-centered peripersonal space representations

TLDR

Neural systems encode peripersonal space (PPS) by integrating nearby visual or auditory stimuli with somatosensory input. The study measured reaction times to tactile stimulation while presenting task‑irrelevant auditory or visual cues at varying distances, across seven experiments, to delineate the critical distance at which these cues enhanced tactile processing on the hand, face, and trunk. The results show that PPS size differs by body part (hand < face < trunk), that approaching stimuli modulate tactile processing across all parts while receding stimuli only affect the hand, and that hand and face PPS extensions vary with relative positioning and congruency but trunk PPS remains constant, indicating at least three body‑part‑specific PPS representations linked to a common trunk reference frame.

Abstract

Abstract Dedicated neural systems represent the space surrounding the body, termed Peripersonal space (PPS), by integrating visual or auditory stimuli occurring near the body with somatosensory information. As a behavioral proxy to PPS, we measured participants’ reaction time to tactile stimulation while task-irrelevant auditory or visual stimuli were presented at different distances from their body. In 7 experiments we delineated the critical distance at which auditory or visual stimuli boosted tactile processing on the hand, face and trunk as a proxy of the PPS extension. Three main findings were obtained. First, the size of PPS varied according to the stimulated body part, being progressively bigger for the hand, then face and largest for the trunk. Second, while approaching stimuli always modulated tactile processing in a space-dependent manner, receding stimuli did so only for the hand. Finally, the extension of PPS around the hand and the face varied according to their relative positioning and stimuli congruency, whereas the trunk PPS was constant. These results suggest that at least three body-part specific PPS representations exist, differing in extension and directional tuning. These distinct PPS representations, however, are not fully independent from each other, but referenced to the common reference frame of the trunk.