Modulation of auditory peripersonal space by approaching and receding sound sources

The peripersonal space (PPS) is defined as the region surrounding the body where we can interact with other objects using our limbs. The representation of objects within PPS depends not only on their physical position but also on other factors, including speed and direction of movement. It has been shown that approaching auditory stimuli can increase PPS extension by making the source appear closer than it actually is, suggesting a possible role for PPS as a warning mechanism that anticipates the time of arrival. We investigated the representation of moving auditory objects within peripersonal space. Stimuli consisted of short white-noise bursts presented in front of the subject (azimuth = 0°) that followed one of three trajectories: looming, receding, or stationary. Sources moved in discrete steps—that is, they were presented at a fixed position for a short period of time, followed by a brief silence, after which they were presented at the next position, repeating this sequence until a set number of steps was reached. After the source finished moving, subjects reported whether they perceived the sound source to be within arm’s reach. Reachability judgments were compared across different trajectories that ended at the same position. Perceived reachability changed depending on the trajectory. We discuss the implications of these results for our understanding of PPS.