Fronto-parietal areas necessary for a multisensory representation of peripersonal space in humans: an rTMS study

A network of brain regions including the ventral premotor cortex (vPMc) and the posterior parietal cortex (PPc) is consistently recruited during processing of multisensory stimuli within peripersonal space (PPS). However, to date, information on the causal role of these fronto-parietal areas in multisensory PPS representation is lacking. Using low-frequency repetitive TMS (rTMS; 1 Hz), we induced transient virtual lesions to the left vPMc, PPc, and visual cortex (V1, control site) and tested whether rTMS affected audio-tactile interaction in the PPS around the hand. Subjects performed a timed response task to a tactile stimulus on their right (contralateral to rTMS) hand while concurrent task-irrelevant sounds were presented either close to the hand or 1 m far from the hand. When no rTMS was delivered, a sound close to the hand reduced RT-to-tactile targets as compared with when a far sound was presented. This space-dependent, auditory modulation of tactile perception was specific to a hand-centered reference frame. Such a specific form of multisensory interaction near the hand can be taken as a behavioral hallmark of PPS representation. Crucially, virtual lesions to vPMc and PPc, but not to V1, eliminated the speeding effect due to near sounds, showing a disruption of audio-tactile interactions around the hand. These findings indicate that multisensory interaction around the hand depends on the functions of vPMc and PPc, thus pointing to the necessity of this human fronto-parietal network in multisensory representation of PPS.