Rubber Hand Illusion Affects Joint Angle Perception

Abstract

The Rubber Hand Illusion (RHI) is a well-established experimental paradigm. It has been shown that the RHI can affect hand location estimates, arm and hand motion towards goals, the subjective visual appearance of the own hand, and the feeling of body ownership. Several studies also indicate that the peri-hand space is partially remapped around the rubber hand. Nonetheless, the question remains if and to what extent the RHI can affect the perception of other body parts. In this study we ask if the RHI can alter the perception of the elbow joint. Participants had to adjust an angular representation on a screen according to their proprioceptive perception of their own elbow joint angle. The results show that the RHI does indeed alter the elbow joint estimation, increasing the agreement with the position and orientation of the artificial hand. Thus, the results show that the brain does not only adjust the perception of the hand in body-relative space, but it also modifies the perception of other body parts. In conclusion, we propose that the brain continuously strives to maintain a consistent internal body image and that this image can be influenced by the available sensory information sources, which are mediated and mapped onto each other by means of a postural, kinematic body model.

Over my fake body: body ownership illusions for studying the multisensory basis of own-body perception

“…While in all the above-mentioned studies the real and fake hands differed in position but were mostly aligned in terms of orientation, other experiments have shown that BOIs can be induced in presence of an additional mismatch in orientation, provided that the fake body (body part) was seen in an anatomically plausible posture. For example, rotating the fake left hand by 44° clockwise did not prevent participants from experiencing the physical touch as if coming from the position of the rubber one, and further led to a recalibration of their perceived elbow joint angle (Butz et al, 2014 ). BOIs were experienced also when the seen fake hand, rotated away from the real one, crossed the body midline (Brozzoli et al, 2012 ; Perez-Marcos et al, 2012 ); but see (Costantini and Haggard, 2007 ; Cadieux et al, 2011 ) for effects in proprioceptive drifts.…”

Spatial numerical estimation within proprioceptive recalibration

“…Following this criteria, two specific estimates across all trials were identified and replaced by the average estimate values of their respective condition and estimation task. We chose this amount of participants as our target sample size, because past studies of rubber hand illusion drawn conclusions from 15-30 participants sample size (e.g., Bekrater-Bodman et al, 2014;Butz et al, 2014;Constantini & Haggard, 2007).…”

“…Nevertheless, RHI was effective in modulating the perceptual judgments by means of attention to hand-space. Also Butz, Kutter and Lorenz (2014) found that the proprioceptive drift not only adjust the perception of the fixed hand in body-relative space, but includes modification of perception in the relative elbow. Both studies explored the relation between proprioceptive drift and estimates of fixed body-space stimuli, but none of them evaluated these estimates in terms of numerical estimation judgements.…”

Toward a Unified Sub-symbolic Computational Theory of Cognition

“…Various researchers have investigated properties of a postural body schema and its plasticity (Holmes and Spence, 2004 ; Cardinali et al, 2009 ; Hoffmann et al, 2010 ; Butz et al, 2010b , 2014 ) 1 . What these treatises all have in common is that temporal predictive sensorimotor structures are learned, which predict sensory changes given motor activities or other sensory dynamics.…”