Peripersonal space (PPS) as a multisensory interface between the individual and the environment, defining the space of the self

Our brain has developed a specific system to represent the space closely surrounding the body, termed pen personal space (PPS). This space has a key functional role as it is where all physical interactions with objects in the environment occur. Here I describe how multisensory neurons in a specific fronto-parietal network map the PPS by integrating tactile stimuli on the body with visual or auditory information related to external objects specifically when they are close to the body. I show how PPS representation is not only multisensory, but actually multisensory-motor, as the PPS system interacts with motor areas to trigger appropriate responses. The extent of PPS is not fixed, but it is shaped by experience, as PPS may encompass farther portions of space, once the individual has interacted with them, (e.g., with tools), or it contracts, if interactions are limited because of external constraints, body, or brain injury. Interactions between the individual and the environment are not only physical but may also be "abstract". Recent data show that PPS adapts as a consequence of technology-mediated or social interactions. Finally, I propose that besides low-level sensory-motor representations of the space around the different parts of the body, mediating body-objects interactions, the multisensory PPS system also underlies a general representation of the self as distinct from the environment and the others. PPS thus supports self-location, contributes to bodily self-consciousness and mediates higher-level cognitive functions.