The role of expectation in multisensory body representation – neural evidence

Abstract

Sensory events contribute to body ownership, the feeling that the body belongs to me. However, the encoding of sensory events is not only reactive, but also proactive in that our brain generates prediction about forthcoming stimuli. In previous studies, we have shown that prediction of sensory events is a sufficient condition to induce the sense of body ownership. In this study, we investigated the underlying neural mechanisms. Participants were seated with their right arm resting upon a table just below another smaller table. Hence, the real hand was hidden from the participant's view and a life-sized rubber model of a right hand was placed on the small table in front of them. Participants observed a wooden plank while approaching - without touching - the rubber hand. We measured the phenomenology of the illusion by means of questionnaire. Neural activity was recorded by means of near-infrared spectroscopy (fNIRS). Results showed higher activation of multisensory parietal cortices in the rubber hand illusion induced by touch expectation. Furthermore, such activity was correlated with the subjective feeling of owning the rubber hand. Our results enrich current models of body ownership suggesting that our multisensory brain regions generate prediction on what could be my body and what could not. This finding might have interesting implications in all those cases in which body representation is altered, anorexia, bulimia nervosa and obesity, among others.

Trait phenomenological control predicts experience of mirror synaesthesia and the rubber hand illusion

“…That is, differences in report between illusion and control conditions may simply be attributable to differing expectancies and response difficulties of suggestion effects, and future RHI studies must ensure that expectancies and difficulty are closely matched across all control and illusion conditions to support claims that suggestion effects have been controlled. Existing evidence that expectation is sufficient to generate the RHI 44,45 (contrast Guterstam) 56 is parsimoniously explained if the RHI is an implicit imaginative suggestion effect.…”

“…Previous findings can be reconstrued in terms of phenomenological control in the rubber hand illusion. For example, effects can occur in unimodal stimulation 54 – 56 ; for mere expectations of touch; 44 or without a fake hand (e.g., the illusion can occur for drawings of hands 57 , or empty space 58 ). As in response to imaginative suggestions presented during hypnotisability screening, there are large individual differences in response to the illusion: while some participants report powerful changes in experience, around 25% are apparently unable to experience the illusion at all 59 , 60 .…”

Altered Processing and Integration of Multisensory Bodily Representations and Signals in Eating Disorders: A Possible Path Toward the Understanding of Their Underlying Causes

“…In this view, the experience of the body is the result of a probabilistic process and, as such, may not reflect the characteristics of the physical body (Badoud and Tsakiris, 2017 ; Ferri et al, 2017 ). More, this vision suggests that the above multisensory processes do not influence the experience of the body only, but can also affect emotion regulation (Riva, 2017b ; Tseng et al, 2015 ).…”

Multisensory correlations—Not tactile expectations—Determine the sense of body ownership

“…In the body ownership literature, there is currently an ongoing debate relating to whether sensory predictions may alter the perception of an artificial limb. Specifically, it has been argued that the mere expectation of a tactile event being about to occur on a rubber hand is sufficient to elicit a sense of ownership over that limb [4–6], which contradicts the leading view in the field that ownership illusions require correlated sensory signals from at least two sensory modalities (or somatosensory submodalities) [7–11]. However, a recent study from our group investigating the “magnetic touch illusion” failed to find an effect of such “tactile expectations” on limb ownership [12], sparking a scientific debate [13].…”

“…However, a recent study from our group investigating the “magnetic touch illusion” failed to find an effect of such “tactile expectations” on limb ownership [12], sparking a scientific debate [13]. In this study, we set out to test whether tactile expectations play any role in the generation of magnetic touch illusion [12,14] as well as replicating the basic tactile expectation effect on ownership [4–6].…”