Abstract
Peripersonal space is a multisensory representation of the space near body parts facilitating interactions with the close environment. Studies on non-human and human primates converge in showing that peripersonal space (PPS) is a body-part-centred representation that guides actions. Because of these characteristics, growing confusion conflates peripersonal and arm-reaching space (ARS) that is the space one’s arm can reach. Despite neuroanatomical evidence favors their distinction, whether PPS and ARS tap into different spatial representations remains poorly understood. Here, in five experiments we found that PPS differs from ARS in male and female human participants (N = 120), as evidenced both by their performance and the modeling of their multisensory facilitation. We mapped multisensory facilitation in detecting touches at the hand, placed in different locations radially within ARS. Results showed that 1) PPS is smaller than ARS; 2) multivariate modeling of spatial patterns of multisensory facilitation predicts well the position of the participants’ hand within ARS; 3) multisensory facilitation maps shift according to changes of hand position, revealing hand-centred coding of PPS, but not ARS; and 4) cross-correlation analyses highlight isomorphic multisensory facilitation maps across hand positions, suggesting their functional similarity to the receptive fields of monkeys’ multisensory neurons. In sharp contrast, ARS mapping produced undistinguishable patterns across hand positions, cross-validating the conclusion that PPS and ARS are distinct. These findings call for a refinement of theoretical models of PPS and ARS, which are relevant in constructs as diverse as action and self representation, (social) interpersonal distance, brain-machine interfaces and neuroprosthetics.
Significance Statement The peripersonal space (PPS) is a multisensory interface allowing us to interact with objects in the space close to our body-parts, playing a fundamental role for the defense of the body and for the motor control of actions. Recent research has conflated PPS with the arm-reaching space (ARS), that is whole space reachable by the arm. However, there is actually no evidence supporting this equivalence and the anatomical and functional differences between PPS and ARS have been largely overlooked. In this paper, we frame the theoretical issue in depth, validate a novel methodological paradigm across five experiments, and eventually report robust and cross-validated evidence for the distinction between PPS and ARS, supported by both multivariate and univariate analyses.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Conflict of Interest: The authors declare no competing financial interests.
