On the contribution of overt tactile expectations to visuo-tactile interactions within the peripersonal space

Abstract

Since the discovery of neural regions in the monkey brain that respond preferentially to multisensory stimuli presented in proximal space, researchers have been studying this specialised spatial representation in humans. It has been demonstrated that approaching auditory or visual stimuli modulate tactile processing, while they are within the peripersonal space (PPS). The aim of the current study is to investigate the additional effects of tactile expectation on the PPS-related multisensory interactions. Based on the output of a computational simulation, we expected that as tactile expectation increases rapidly during the course of the motion of the visual stimulus, the outcome RT curves would mask the multisensory contribution of PPS. When the tactile expectation remains constant during the motion, the PPS-related spatially selective multisensory processes become apparent. The behavioural results on human experiments followed the pattern predicted by the simulation. That is, rapidly changing levels of tactile expectation, caused by dynamic visual stimuli, masks the outcome of the multisensory processes within peripersonal space. This indicates that both PPS-related multisensory interactions and tactile expectations play an important role in anticipating and responding to interactions with the body.

Peripersonal space boundaries around the lower limbs

“…Many studies that have examined PPS in humans have focused on the upper body (Canzoneri et al 2012;Teneggi et al 2013;Ferri et al 2015a, b;Serino et al 2015;Kandula et al 2015Kandula et al , 2017de Haan et al 2016). This is logical as the early neurophysiological investigations in monkeys mainly focused on the PPS network governing the upper body (e.g., Graziano 2003, 2004;Fogassi et al 1996;Graziano 1999;Graziano et al 1997Graziano et al , 1999Rizzolatti et al 1981b).…”

“…Experiment 1 To measure PPS boundaries, we used a visuo-tactile interaction task using dynamic visual stimuli [similar to the audio-visual interaction tasks in Canzoneri et al (2012) and Serino et al (2015) and to investigations in our lab: Kandula et al (2017) andde Haan et al (2016)]. The task and stimuli were designed and controlled by a custom MATLAB script.…”

“…Haegens et al (2011)]. Moreover, recent investigations in our lab have revealed that the optimal ratio of real to catch trials in this paradigm is 1:1 (Kandula et al 2017). The real and catch trials were intermixed throughout the experiment, and randomized between participants.…”

“…To examine the relationship between tactile response times and visual stimulus location, we fitted the mean reaction times to both linear and sigmoidal functions [mimicking the analyses of Canzoneri et al (2012), Ferri et al (2015a, Serino et al (2015), Kandula et al (2017), and Taffou and Viaud-Delmon (2014)]. The fits of these functions were then compared to evaluate which function better described the data.…”

“…One's boundary between peri-and extra-personal space can be approximated by asking participants to respond to tactile input while in the presence of irrelevant looming auditory or visual information (Canzoneri et al 2012(Canzoneri et al , 2013bNoel et al 2015;Serino et al 2015;de Haan et al 2016;Kandula et al 2017), as the PPS network is particularly sensitive to dynamic (especially approaching) sensory information. In such a paradigm, a tactile stimulus (vibration) is applied to the participants' limb at different time points along the trajectory of a looming auditory or visual stimulus, and participants are asked to respond (as quickly as possible) to the tactile stimulus only.…”