The multifaceted interplay between environment and tactile modalities in shaping multisensory integration

Human experience is grounded in the continuous integration of sensory information across modalities, allowing the body to serve as the central reference for perceiving and interacting with the surrounding world. Within this framework, peripersonal space (PPS)—the space immediately surrounding the body—acts as a dynamic interface where visual, auditory and tactile signals converge to support interaction, protection, and social connection. Far from being static, PPS emerges as a dynamic construct that flexibly adapts to the changing interplay between environmental context, bodily state, and affective experience. This dissertation explores how distinct tactile modalities and environmental contexts modulate PPS representation, combining behavioural and neuroimaging approaches to uncover the neural and functional bases of body-centred multisensory processing. The first study examined whether environmental features influence the plasticity of PPS. Using immersive virtual reality, participants performed motor interactions in architectural spaces differing in spatial configuration. Results revealed that environmental affordances influence PPS remapping: interactions within spatially open settings induced a plastic expansion of near-body space, whereas constrained configurations limited such recalibration. These findings extend the notion of PPS plasticity to the domain of architectural context, highlighting how spatial design can recalibrate the way the brain anchors sensory information to the body and to action. The second study investigated how affective and discriminative tactile modalities contribute to the representation of peripersonal space. While previous research has conceptualized PPS primarily as a sensorimotor interface supporting goal-directed action and defence, this study explored whether socially meaningful, affective touch—mediated by C-tactile afferents—could give rise to a distinct mapping of near-body space. Results revealed that affective touch, delivered at CT-optimal velocity, elicited a significantly broader PPS compared to discriminative touch. This finding provides the first direct evidence that emotionally salient tactile signals are spatially integrated within body-centred multisensory processing, supporting the existence of two complementary systems: an Instrumental PPS, grounded in discriminative touch and related to object-oriented actions, and a Social PPS, grounded in affective touch and linked to affiliative body-environment interactions. Building on these behavioural findings, the third study employed functional MR to investigate the neural mechanisms underlying spatialized visuo-tactile integration of affective and discriminative touch. Preliminary findings revealed that these two tactile modalities engaged partially overlapping visuo-tactile circuit centred in the postcentral and opercular cortices, supporting the integration of tactile and visual inputs near the body. Interestingly, discriminative touch paired with visual cues in near space elicited a neural pattern more closely resembling that of affective touch combined with visual stimuli in far space, engaging additional posterior parietal regions involved in spatial mapping. Analyses within functionally defined regions showed enhanced activation for affective relative to discriminative touch in the central operculum when visual cue was presented near the hand, and a general affective advantage in the postcentral cortex irrespective of distance, suggesting a privileged role of affective touch in multisensory body-related processing. Although these results are preliminary, they offer the first functional delineation of the neural circuits supporting social and instrumental PPS. These findings offer a comprehensive view of how the brain organizes multisensory information around the body, integrating environmental and affective signals to shape near-body perception. By combining evidence from behavioural and neuroimaging studies, this work advances our understanding of how peripersonal space flexibly adapts to both contextual and sensory factors, supporting adaptive interaction with the physical and social world.