Vestibular contributions to a right-hemisphere network for bodily awareness: Combining galvanic vestibular stimulation and the “Rubber Hand Illusion”

Abstract

An altered sense of one's own body is a common consequence of vestibular damage, and also of damage to vestibular networks in the right hemisphere. However, few experimental studies have investigated whether vestibular signals contribute to bodily awareness. We addressed this issue by combining an established experimental model of bodily awareness (Rubber Hand Illusion -RHI) with galvanic vestibular stimulation (GVS) in healthy participants. Brief left anodal and right cathodal GVS (which predominantly activates vestibular networks in the right hemisphere), or right anodal and left cathodal GVS, or sham stimulation were delivered at random, while participants experienced either synchronous or asynchronous visuo-tactile stimulation of a rubber hand and their own hand. The drift in the perceived position of the participant's hand towards the rubber hand was used as a proxy measure of the resulting multisensory illusion of body ownership. GVS induced strong polarity-dependent effects on this measure of RHI: left anodal and right cathodal GVS produced significantly lower proprioceptive drift than right anodal and left cathodal GVS. We suggest that vestibular inputs influence the multisensory weighting functions that underlie bodily awareness: the right hemisphere vestibular projections activated by the left anodal and right cathodal GVS increased the weight of intrinsic proprioceptive signals about hand position, and decreased the weight of visual information responsible for visual capture during the RHI.

From multisensory integration in peripersonal space to bodily self‐consciousness: from statistical regularities to statistical inference

“…Similarly, while the vestibular system is an important component in bodily self‐consciousness (a sensory modality that is by default “global”), this sensory modality does not appear to strongly contribute to the RHI (but see Refs. and ), which instead importantly involves proprioceptive inputs.…”

Vestibular modulation of multisensory integration during actual and vicarious tactile stimulation

“…This may explain some of the previous conflicting findings in vestibular stimulation studies (e.g. [21,23] vs [22,45,46]). When a rubber hand is in a plausible position in space, allowing its integration in participants' body representation (as in our previous and current studies), vestibular signals may contribute to solve perceptual ambiguity by weighting visual signals more than proprioceptive ones.…”

“…see Galvanic Vestibular Stimulation, i.e. GVS [20], studies [21,22]). A previous study from our group [23] aimed to clarify these conflicting findings, whilst assessing how vestibular and interoceptive signals (i.e.…”

The vestibular system

“…This suggests that GVS increased visual capture, a dominance of visual signals over proprioceptive signals [47,91]. Second, mislocalization of the participant's hand, which appears closer to the rubber hand, was lessened by right cathodal GVS [92], suggesting an influence of vestibular signals on proprioception [93,94]. Altogether, healthy participants data suggest that vestibular stimulation may modulate visual and proprioceptive signal integration (for recent accounts, see [95,96,97 & ]) in a more specific way than general hemispheric activation. ]…”