Peripersonal Space (PPS) is defined as the space close to the body where all interactions between the individual and the environment take place. Behavioural experiments on PPS exploit multisensory integration, using Multisensory Visuo-Tactile stimuli (MVT), whose visual and tactile components target the same body part (i.e. the face, the hand, the foot). However, the effects of visual and tactile stimuli targeting different body parts on PPS representation are unknown, and the relationship with the RTs for Tactile-Only stimuli is unclear. In this study, we addressed two research questions: (1) if the MVT-RTs are independent of Tactile-Only-RTs and if the latter is influenced by time-dependency effects, and (2) if PPS estimations derived from MVT-RTs depend on the location of the Visual or Tactile component of MVTs. We studied 40 right-handed participants, manipulating the body location (right hand, cheek or foot) and the distance of administration. Visual and Tactile components targeted different or the same body parts and were delivered respectively at five distances. RTs to Tactile-Only trials showed a non-monotonic trend, depending on the delay of stimulus administration. Moreover, RTs to Multisensory Visuo-Tactile trials were found to be dependent on the Distance and location of the Visual component of the stimulus. In conclusion, our results show that Tactile-Only RTs should be removed from Visuo-Tactile RTs and that the Visual and Tactile components of Visuo-Tactile stimuli do not necessarily have to target the same body part. These results have a relevant impact on the study of PPS representations, providing new important methodological information.

Behavioural studies on Multisensory Peripersonal Space (PPS) representations are based on seminal findings in single-cell recordings.A classic experimental paradigm used to assess PPS is the Multisensory Integration Paradigm. In this paradigm Visuo-Tactile stimuli are administrated to participants. According to the paradigm, the tactile component vibrates when the visual component, approaching the participant, reaches a specific distance. Participants must detect the tactile component. Reaction times (RTs) are faster with closer visual stimuli. This effect is classically interpreted as a manifestation of PPS representation.However, the Visual and Tactile components are usually targeting at the same body part, and Tactile-Only RTs are considered constant.In this study we formally addressed two research questions: i) whether the Multisensory Visuo-Tactile RTs are independent from Tactile-Only RTs and whether the latter are influenced by time-dependency effects; and ii) whether PPS estimations derived from Multisensory Visuo-Tactile RTs depend on the location of the Visual or Tactile component of the stimuli.We studied 40 right-handed participants, in a repeated-measure design, crossing the position of the Tactile and Visual components of stimuli across the face, the hand and the foot, and 5 distances. Each trial could be Visuo-Tactile, Tactile-Only or a Catch trial.Frequentist and Bayesian analysis demonstrated that Tactile-Only RTs follow a non-monotonic trend, depending on the delay of stimulus administration. Furthermore, according to our findings, Visuo-Tactile RTs were proved to be dependent on Distance and location of the Visual component of the stimulus. Our results lead to the conclusion that Tactile-Only RTs should be removed from Visuo-Tactile RTs and that the Visual and Tactile components of Visuo-Tactile stimuli do not necessarily have to target at the same body part.These results may have an advantageous impact on the study of PPS representations, providing new and important methodological information.