Losing One's Hand: Visual-Proprioceptive Conflict Affects Touch Perception

Abstract

BackgroundWhile the sense of bodily ownership has now been widely investigated through the rubber hand illusion (RHI), very little is known about the sense of disownership. It has been hypothesized that the RHI also affects the ownership feelings towards the participant's own hand, as if the rubber hand replaced the participant's actual hand. Somatosensory changes observed in the participants' hand while experiencing the RHI have been taken as evidence for disownership of their real hand. Here we propose a theoretical framework to disambiguate whether such somatosensory changes are to be ascribed to the disownership of the real hand or rather to the anomalous visuo-proprioceptive conflict experienced by the participant during the RHI.Methodology/Principal FindingsIn experiment 1, reaction times (RTs) to tactile stimuli delivered to the participants' hand slowed down following the establishment of the RHI. In experiment 2, the misalignment of visual and proprioceptive inputs was obtained via prismatic displacement, a situation in which ownership of the seen hand was doubtless. This condition slowed down the participants' tactile RTs. Thus, similar effects on touch perception emerged following RHI and prismatic displacement. Both manipulations also induced a proprioceptive drift, toward the fake hand in the first experiment and toward the visual position of the participants' hand in the second experiment.Conclusions/SignificanceThese findings reveal that somatosensory alterations in the experimental hand resulting from the RHI result from cross-modal mismatch between the seen and felt position of the hand. As such, they are not necessarily a signature of disownership.

The plausibility of visual information for hand ownership modulates multisensory synchrony perception

“…moving the index finger, on the left side of the hand, caused a movement on the right side of the rendered hand). Previous research has shown visualproprioceptive mismatches can influence somatosensory and multisensory perception (Folegatti et al 2009;Pavani et al 2000). Thus, both factors, the visual plausibility and the spatial congruency, could potentially account for the perceptual modifications we have found in Experiment 2.…”

Embodiment, ownership and disownership

“…as evidence that the biological hand is replaced by its artificial counterpart. However, a similar slowing down of tactile processes was found following prismatic displacement (Folegatti et al, 2009). 4 It should thus be related to visuo-proprioceptive conflict rather than to disownership.…”

“…In questionnaires, participants disagree when asked if they felt as if their biological hand had disappeared, but they also disagree when asked if they felt as if they had three hands (Longo et al, 2008). At the physiological and behavioral level, it was found a decrease in skin temperature of the biological hand following the RHI, as well as a slowing down of tactile processes (Folegatti, de Vignemont, Pavani, Rossetti, & Farnè, 2009;Moseley et al, 2008). These results have been interpreted by Moseley and coll.…”

Body Integrity Identity Disorder: Deranged Body Processing, Right Fronto-Parietal Dysfunction, and Phenomenological Experience of Body Incongruity

“…In these CRPS patients, when the affected limb is moved into the opposite "good" side of space it becomes warmer and, accordingly, when the good limb is moved into the affected side of space it is perceived to be cooler. Sensory information is principally processed in body-space co-ordinates, whereby crossing the limbs over the body midline slows processing of tactile sensory stimuli (Schicke and Röder 2006) and reduces the accuracy of proprioceptive localisation of body parts (Folegatti et al 2009); however, in patients with asomatognosia placing the limbs into attended body space can effectively restore multisensory processing (Moro et al 2004). Collectively, these findings raise the question whether BIID relates to disintegration of multisensory information that is limb-specific or pertains to body-space co-ordinates (e.g., see: (Moseley et al 2011)).…”