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

Abstract

Can the mere expectation of a sensory event being about to occur on an artificial limb be sufficient to elicit an illusory sense of ownership over said limb? This issue is currently under debate and studies using two different paradigms have presented conflicting results. Here, we employed the two relevant paradigms, namely, the magnetic touch illusion and the “tactile expectation” version of the rubber hand illusion, to clarify the role of tactile expectations in the process of attributing ownership to limbs. The illusory senses of ownership and ‘magnetic touch’ were quantified using questionnaires, threat-evoked skin conductance responses and a combination of motion tracking synchronized with real-time subjective ratings and skin conductance. The results showed that the magnetic touch illusion was dependent on concurrent visual and tactile stimulation and that visually induced tactile expectations alone were insufficient. Moreover, in this study, tactile expectations were not associated with the rubber hand illusion, neither in terms of subjective ratings nor skin conductance changes. Together, these findings contradict the notion that the brain uses predictions of upcoming sensory events to determine whether or not a limb belongs to the self, and, instead, emphasize the importance of correlated multisensory information.

Fluidity of gender identity induced by illusory body-sex change

“…Follow-up comparisons for each condition used the following linear mixed model: reaction time ~ 1 + block + 1|id + 1|item. For 27 the analysis presented in Fig. 2f, we used the following model: reaction time ~ 1 + body*synchrony*block*ownership + 1|id + 1|item.…”

Fluidity of gender identity induced by illusory body-sex change

“…The full-body ownership illusion, similar to the rubber hand illusion involving a single limb [34][35][36][37] , occurs when visual, tactile, proprioceptive, and other sensory signals from the body are combined at the central level into a coherent multisensory representation of one's own body [24][25][26]30 . Body ownership illusions involving limbs 37 and full bodies 31,33,38 are related to increased neural activity in regions of the frontal and parietal association cortices that are related to multisensory integration, such as the premotor and intraparietal cortices.…”

Sustained rubber hand illusion after the end of visuotactile stimulation with a similar time course for the reduction of subjective ownership and proprioceptive drift

“…Furthermore, knowledge about the persistence and slow decay of the rubber hand illusion after visuotactile stimulation stops is relevant for the design of efficient and well-planned studies, for example, emphasizing the need to consider possible carryover effects that might arise from a sustained feeling of ownership across trials. Moreover, the sustained nature of the rubber hand illusion is also good news for experimenters who want to present various tests after the visuotactile stimulation stops, for example, reaction time tasks (Reader et al, 2020) or registration of threat-evoked SCR responses (Guterstam et al, 2019;Petkova & Ehrsson, 2009), as our data suggest that the time windows of one to ten seconds that are often used are well within a period when the illusion is still maintained. Finally, our results have a bearing on applied neuroscience and the development of advanced prosthetic limbs that feel more like real limbs (Collins et al, 2017;Ehrsson et al, 2008).…”

“…The aim of experiment two was to better control for the amount of time the participant had their eyes open and looked at the rubber hand during the different phases of the testing. We know that visual feedback from looking at the rubber hand can influence illusion strength due to visuoproprioceptive integration (Durgin et al, 2007;Kalckert & Ehrsson, 2012;Samad et al, 2015;Trojan et al, 2018;Walsh et al, 2011), even though such effects can be small and the illusion cannot typically be elicited by looking at the rubber hand alone (Guterstam et al, 2019). However, if only viewing the rubber hand can lead to a slower reduction for one of our outcome measures, we theorized this could affect the relative time course of proprioceptive drift and ownership, and therefore we designed the second experiment to better control for this factor throughout all time points sampled from 0 s to 300 s.…”