The modularity of peripersonal space representations: the influence of the vision and tactile sensation on different body parts

Peripersonal space (PPS) representation is described as a graded field of the space closely surrounding the body, characterized by a modular organization, with different PPS extensions for each body area. However, no studies systematically investigated the possible integration of different body areas in PPS representations. By means of a visuo-tactile paradigm, where visual stimuli approached the body, and a tactile stimulus could be delivered at 5 different positions of the visual stimuli (196, 147, 98, 49 and 1 cm), 42 right-handed participants (21 males) had to say “TOH” when they felt the tactile stimulus. The task was repeated in nine conditions, given by the crossing of the position of the visual stimuli (towards the right Hand, Face or Foot) and the position of the tactile stimulus (right Hand, Face or Foot). In each condition 48 stimuli were administered. Reaction times were analysed by means of generalized logit Bayesian multilevel models, in order to have an estimation of the position of the mid-point and the steepness of the generalized logit curve, as indexes of the boundary and the gradation of the curves of the PPS representations, respectively. Results showed that the position of the visual stimuli explained both the boundaries (BF10=3.73) and the gradations (BF10=4.21) of the different PPS representations. Therefore, the modularity of PPS representations seems to be a function of the body-part observed, and it is not necessary a correspondence between the body-part target of visual and tactile stimuli to estimate it.