Peripersonal and reaching space differ: Evidence from their spatial extent and multisensory facilitation pattern

A. Zanini,E. Koun,E. Blini,I. Patané,C. Brozzoli,R. Salemme,A. Farnè

doi:10.3758/s13423-021-01942-9

Abstract

Peripersonal space (PPS) is a multisensory representation of the space near body parts facilitating interactions with the close environment. Studies on non-human and human primates agree in showing that PPS is a body part-centered representation that guides actions. Because of these characteristics, growing confusion surrounds peripersonal and arm-reaching space (ARS), that is the space one’s arm can reach. Despite neuroanatomical evidence favoring their distinction, no study has contrasted directly their respective extent and behavioral features. Here, in five experiments (N = 140) we found that PPS differs from ARS, as evidenced both by participants’ spatial and temporal performance and by its modeling. We mapped PPS and ARS using both their respective gold standard tasks and a novel multisensory facilitation paradigm. Results show that: (1) PPS is smaller than ARS; (2) multivariate analyses of spatial patterns of multisensory facilitation predict participants’ hand locations within ARS; and (3) the multisensory facilitation map shifts isomorphically following hand positions, revealing hand-centered coding of PPS, therefore pointing to a functional similarity to the receptive fields of monkeys’ multisensory neurons. A control experiment further corroborated these results and additionally ruled out the orienting of attention as the driving mechanism for the increased multisensory facilitation near the hand. In sharp contrast, ARS mapping results in a larger spatial extent, with undistinguishable patterns across hand positions, cross-validating the conclusion that PPS and ARS are distinct spatial representations. These findings show a need for refinement of theoretical models of PPS, which is relevant to constructs as diverse as self-representation, social interpersonal distance, and motor control.

Highlights

Padova, Italy 4 Hospices Civils de Lyon, Neuro-immersion – Mouvement et Handicap, Lyon, France 5 Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy 6 Department of Neurobiology, Care Sciences and Society, AgingResearch Center, Karolinska Institutet, Stockholm, SwedenSeminal studies described multisensory neurons in primates’ fronto-parietal regions coding for the space surrounding the body, termed peripersonal space (PPS) (Colby et al, 1993;Graziano & Gross, 1993 ; Rizzolatti et al, 1981a, 1981b)
All participants reported normal or corrected-to-normal vision, normal tactile sensitivity, and no history of psychiatric disorders. They gave their informed consent before taking part in the study, which was approved by the local ethics committee (Comité d’Evaluation de l’Ethique de l’Inserm, n° 17-425, IRB00003888, IORG0003254, FWA00005831) and was carried out in accordance with the Declaration of Helsinki
We tested the effect of VT stimulation over ten uniformly spaced positions, to obtain a fine-grained map of patterns of multisensory facilitation

Summary

Introduction

Seminal studies described multisensory neurons in primates’ fronto-parietal regions coding for the space surrounding the body, termed peripersonal space (PPS) (Colby et al, 1993;Graziano & Gross, 1993 ; Rizzolatti et al, 1981a, 1981b). These neurons display visual receptive fields anchored to tactile ones and protruding over a limited area (~5 to 30 cm) from specific body parts (e.g., the hand) (Graziano & Gross, 1993; Rizzolatti et al, 1981a, 1981b). The consequences of this conflation on spatial models of multisensory facilitation have to date been neglected, despite the crucial role it plays in sensorimotor control (Makin et al, 2017; Suminski et al, 2009, 2010) and the study of the bodily self (Blanke et al, 2015; Makin et al, 2008)

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