Multisensory-driven facilitation within the peripersonal space is modulated by the expectations about stimulus location on the body

Abstract

Compelling evidence from human and non-human studies suggests that responses to multisensory events are fastened when stimuli occur within the space surrounding the bodily self (i.e., peripersonal space; PPS). However, some human studies did not find such effect. We propose that these dissonant voices might actually uncover a specific mechanism, modulating PPS boundaries according to sensory regularities. We exploited a visuo-tactile paradigm, wherein participants provided speeded responses to tactile stimuli and rated their perceived intensity while ignoring simultaneous visual stimuli, appearing near the stimulated hand (VTNear) or far from it (VTFar; near the non-stimulated hand). Tactile stimuli could be delivered only to one hand (unilateral task) or to both hands randomly (bilateral task). Results revealed that a space-dependent multisensory enhancement (i.e., faster responses and higher perceived intensity in VTNear than VTFar) was present when highly predictable tactile stimulation induced PPS to be circumscribed around the stimulated hand (unilateral task). Conversely, when stimulus location was unpredictable (bilateral task), participants showed a comparable multisensory enhancement in both bimodal conditions, suggesting a PPS widening to include both hands. We propose that the detection of environmental regularities actively shapes PPS boundaries, thus optimizing the detection and reaction to incoming sensory stimuli.

Spatial proximity to others induces plastic changes in the neural representation of the peripersonal space

“… 3 , 4 , 5 In non-human primates, there is extensive evidence that multimodal PPS neurons are able to map the body boundaries, as their firing rate decreases whereas the distance between the stimulated body district and the concurrent (visual or auditory) stimuli increases. 3 , 6 Analogously, in humans, visual or auditory stimuli occurring at a limited distance from the body speed up the behavioral responses to tactile stimuli 7 , 8 , 9 and boost the neural activity (e.g., 10 , 11 , 12 , 13 ). In both human and non-human primates, the PPS representation is known to be highly plastic, changing with experience (e.g., 14 , 15 , 16 , 17 , 18 , 19 ).…”

The self, its body and its brain

“…However, every feeling, thought and behaviour occurs in the context of the body, and thus it is intuitive that embodied experience may impact our mental processing and sense of self, and vice versa. Examples of this relationship can be found within papers from the current Collection, with the suggestion that the way we process external stimuli is mediated by an interaction between our own expectations and their locations relative to the body 3 . Additionally, many people with psychiatric conditions experience differences in bodily experience.…”

“…The self, its body and its brain Morten Overgaard 1* , Catherine Preston 2 & Jane Aspell 3 The body is intrinsic to our sense of self and as such, any theoretical account of the self should also include contributions of the body. This Collection incorporates a series of papers that demonstrate the inextricable relationship between body and self.…”

The Body in Neurosciences: Representation, Perception and Space Processing

“…This can be attributed to the importance of sensory events that take place in the immediate vicinity of the body. Indeed, such events play a critical role in defining the spatial boundaries of the bodily self, facilitating goal-directed actions and detecting potential threats [33]. Instead, little is known about another relevant feature of sensorial stimulation: the size of the stimulated area.…”