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

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, crossvalidating 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 crossvalidated evidence for the distinction between PPS and ARS, supported by both multivariate and univariate analyses.

Predicting Upcoming Events Occurring in the Space Surrounding the Hand

“…Our results suggest that at least partially separate parietofrontal networks could be at play in anticipating motor or tactile events experienced by others. In a similar manner, employing a set of psychophysical tasks, Zanini et al [ 23 ] argued that the peripersonal space and the within arms' reach space representations are not superimposable. Studies using EEG [ 46 ], TMS [ 47 ], and fMRI [ 6 , 43 , 48 ] have confirmed that a multisensory representation of peripersonal space takes place in both the parietal and prefrontal areas.…”

“…Furthermore, as suggested by recent behavioral studies, the networks in the brain coding for the space of action (“arm reaching space”) and the peripersonal space could be at least partially segregated. An important finding is that the space within arms' reach is not body part centered, while the peripersonal space is [ 23 ]. As a consequence, the predictive coding signatures associated with each of these two networks might also differ.…”

Representation and Perception of the Body in Space

“…Finally, other measures have been proposed to capture a basic form of near-far differentiation in spatial processing, such as the line bisection task Lourenco, 2006, 2007) and reachability judgements (Costantini et al, 2010;Cardellicchio, Sinigaglia and Costantini, 2011;Delevoye-Turrell, Vienne and Coello, 2011). However, these tasks based on reachability judgments capture a larger, shoulder-centered representation of the reaching space that is distinguished from a multisensory body-parts-centered PPS representation sustaining both proactive and defensive behaviors (De Vignemont et al, in press;Zanini et al, 2020).…”

The thickness of the ventral medial prefrontal cortex (vmPFC) predicts the self-prioritization effect (SPE) on the interaction between spatial reference frames and spatial domains

“…Previous studies have suggested that the space domain is divided into near (within the range of the arm) and far (beyond the range of the arm) spaces based on the hand-reaching distance 5,8,9 . According to the perception/action modal, the dorsal stream is implicated in near-space processing when individuals conduct an action and manipulation representation, and the ventral stream is implicated in far-space processing when individuals conduct a perception representation [10][11][12][13] .…”