How Visual Experience Shapes Peripersonal Space Boundaries: Evidence from Blindness

Peripersonal space (PPS) is a multisensory-motor interface that enables effective interaction with the surrounding environment. Although vision is typically the primary sensory modality involved in spatial processing, how the absence of visual experience affects PPS organization remains largely unclear. The present study addressed this question by using blindness as a model of visual deprivation, examining whether and how visual experience shapes the spatial boundaries of PPS. We recruited congenitally blind individuals, late-blind individuals, and blindfolded sighted controls, and assessed the two fundamental PPS functions: multisensory integration and defensive protection. In Experiment 1, participants completed an audio-tactile interaction task to determine the spatial extent of multisensory PPS. Blind individuals showed a multisensory facilitation effect comparable to sighted participants, with similar spatial modulation, indicating that visual experience does not influence PPS boundaries when defined by multisensory processing. In contrast, Experiment 2 revealed that defensive PPS is strongly modulated by visual experience: using the hand-blink reflex paradigm, we found no spatial modulation in congenitally blind individuals, a partially preserved modulation in late-blind individuals, and a typical distance-dependent increase in sighted controls. These findings suggest that defensive PPS is highly plastic and reorganizes in response to the sensory input available, potentially extending as a compensatory protective mechanism in blindness. Taken together, this work provides the first integrated examination of both multisensory and defensive PPS in visual deprivation. By demonstrating a differential contribution of vision across PPS functions, the study advances our understanding of PPS organization and offers new insights into sensory brain plasticity