Somatotopy-independent reduction of audio-tactile intersensory facilitation for looming sounds within the peripersonal space during arm movements execution

Auditory events occurring in the peripersonal space (PPS) or near specific body parts such as the peritrunk (PTS) and perihand (PHS) space, have been shown to facilitate tactile processing in a somatotopic manner. Furthermore, previous research has demonstrated that audio-tactile intersensory effects are influenced by the execution of full body transport movements (i.e., walking or cycling), so that far-off auditory stimuli that approach the body in a direction coherent with the movement facilitate tactile processing on the body. However, whether these motor-related intersensory effects are modulated by non-transport movements is not known. Here, in two experiments, we sought to determine whether audio-tactile intersensory effects for looming sounds in the PHS and PTS are somatotopically modulated by arm movement compared to when being still. By controlling the role of temporal expectation, we confirm that looming sounds enhance tactile reactivity as they approach the participants' hand and trunk. We further show that this facilitation is eliminated by limb movements, regardless of somatotopy, and that executing movements blur the distinction between intersensory effects in extrapersonal and peripersonal space. These results contribute to understanding the complex relation between motor execution and intersensory processing.