Neural adaptation accounts for the dynamic resizing of peripersonal space: evidence from a psychophysical-computational approach

Interactions between the body and the environment occur within the peripersonal space (PPS), the space immediately surrounding the body. The PPS is encoded by multisensory (audio-tactile, visual-tactile) neurons that possess receptive fields (RFs) anchored on the body and restricted in depth. The extension in depth of PPS neurons’ RFs has been documented to change dynamically as a function of the velocity of incoming stimuli, but the underlying neural mechanisms are still unknown. Here, by integrating a psychophysical approach with neural network modeling, we propose a mechanistic explanation behind this inherent dynamic property of PPS. We psychophysically mapped the size of participant’s peri-face and peri-trunk space as a function of the velocity of task-irrelevant approaching auditory stimuli. Findings indicated that the peri-trunk space was larger than the peri-face space, and, importantly, as for the neurophysiological delineation of RFs, both of these representations enlarged as the velocity of incoming sound increased. We propose a neural network model to mechanistically interpret these findings: the network includes reciprocal connections between unisensory areas and higher order multisensory neurons, and it implements neural adaptation to persistent stimulation as a mechanism sensitive to stimulus velocity. The network was capable of replicating the behavioral observations of PPS size remapping and relates behavioral proxies of PPS size to neurophysiological measures of multisensory neurons’ RF size. We propose that a biologically plausible neural adaptation mechanism embedded within the network encoding for PPS can be responsible for the dynamic alterations in PPS size as a function of the velocity of incoming stimuli. NEW & NOTEWORTHY Interactions between body and environment occur within the peripersonal space (PPS). PPS neurons are highly dynamic, adapting online as a function of body-object interactions. The mechanistic underpinning PPS dynamic properties are unexplained. We demonstrate with a psychophysical approach that PPS enlarges as incoming stimulus velocity increases, efficiently preventing contacts with faster approaching objects. We present a neurocomputational model of multisensory PPS implementing neural adaptation to persistent stimulation to propose a neurophysiological mechanism underlying this effect.

Attending to Bullying: A Psychophysical Approach to Understanding Peer Aggression and Victimization

Intervention and prevention programs for peer aggression in schools have largely been constructed with the assumption that aggressive children will pay more attention to aggressive stimuli in their social environment. However, this hypothesis has never been tested with direct measures of attention. Thus, my honours thesis project is investigating how participants with a history of peer aggression involvement as a perpetrator or victim direct their attention in photographs depicting scenarios of peer aggression. Based on answers in a questionnaire, participants were divided into three groups: (1) those with a history of perpetrating peer aggression, (2) those with a history of being victimized by peer aggression and (3) those with no history of peer aggression involvement. The experimental study was conducted on an eyetracker, which measured where participants were looking as they viewed 48 photographs. The photographs depicted preadolescent children in scenes of group or peer‐to‐peer interactions that were either aggressive or non‐aggressive. I predict that those with a history of aggression will pay more attention to the aggressors in the scenes more often than those with a history of victimization or the control group. This investigation will give direct evidence regarding how attention in social scenes is affected by a history of peer aggression involvement. A better understanding of how attentional processes are affected by a history of peer aggression involvement will allow for the development of more effective intervention and prevention programs for peer aggression in schools.