Close to me but unreachable: Spotting the link between peripersonal space and empathy.

The space surrounding the body (i.e., peripersonal space, PPS) has a crucial impact on individuals' interaction with the environment. Research showed that interaction within the PPS increases individuals' behavioral and neural responses. Furthermore, individuals' empathy is affected by the distance between them and the observed stimuli. This study investigated empathic responses to painfully stimulated or gently touched faces presented within the PPS depending on the presence vs. absence of a transparent barrier erected to prevent interaction. To this aim, participants had to determine whether faces were painfully stimulated or gently touched while their electroencephalographic (EEG) signals were recorded Brain activity (i.e., event-related potentials [ERPs], source activations) was separately compared for the two types of stimuli (i.e., gently touched vs. painfully stimulated faces) across two barrier conditions: (a) no barrier between participants and the screen (i.e., no-barrier) and (b) a plexiglass barrier erected between participants and the screen (i.e., barrier). While the barrier did not affect performance behaviorally, it reduced cortical activation at both the ERP and source activation levels in brain areas that regulate interpersonal interaction (i.e., primary, somatosensory, premotor cortices; inferior frontal gyrus). These findings suggest that the barrier, precluding the possibility of interacting, reduced the observer's empathy.