Rubber hand illusion induced by touching the face ipsilaterally to a deprived hand: evidence for plastic “somatotopic” remapping in tetraplegics

Abstract

Background: Studies in animals and humans indicate that the interruption of body-brain connections following spinal cord injury (SCI) leads to plastic cerebral reorganization.Objective: To explore whether inducing the Rubber Hand Illusion (RHI) via synchronous multisensory visuo-tactile bodily stimulation may reveal any perceptual correlates of plastic remapping in SCI. Methods:In 16 paraplegic, 16 tetraplegic and 16 healthy participants we explored whether RHI may be induced by tactile stimuli involving not only the left hand but also the left hemi-face. Touching the participants actual hand or face was either synchronous or asynchronous with tactile stimuli seen on a rubber hand. We assessed two components of the illusion, namely perceived changes in the real hand in space (indexed by proprioceptive drift) and ownership of the rubber hand (indexed by subjective responses to an ad-hoc questionnaire).Results: Proprioceptive drift and ownership were found in the healthy group only in the condition where the left real and fake hand were touched simultaneously. In contrast, no drift was found in the SCI patients who, however, showed ownership after both synchronous and asynchronous hand stroking. Importantly, only tetraplegics showed the effect also after synchronous face stroking.Conclusions: RHI may reveal plastic phenomena in SCI. In hand representation-deprived tetraplegics, stimuli on the face (represented contiguously in the somatic and motor systems), drive the sense of hand ownership. This hand-face remapping phenomenon may be useful for restoring a sense of self in massively deprived individuals.

Rubber hand illusion highlights massive visual capture and sensorimotor face-hand remapping in a tetraplegic man

“…Importantly this modified RHI paradigm may represent an indirect way to test brain plasticity and body representation in SCI people who experience a dramatic change in body perception and visual representation (Fuentes et al, 2013). Studies on larger samples may allow to support more robust conclusions on possible hand-face remapping mechanisms after spinal cord lesion (Scandola et al, 2013;Scandola et al, 2014) and therefore to understand the role of across-body parts remapping in supporting the sensory side of motor rehabilitation (Lenggenhager et al, 2013;Dietz et al, 2013) as well as the reduction of neuropathic pain (e.g. using virtual reality, Villiger et al, 2011).…”

The Moving Rubber Hand Illusion Reveals that Explicit Sense of Agency for Tapping Movements Is Preserved in Functional Movement Disorders

“…Interestingly, these studies demonstrated that despite abnormalities in the motor system, patients subjectively experienced a strong illusion (Lenggenhager et al, 2012; Scandola et al, 2014; Tidoni et al, 2014; Burin et al, 2015). Caution is warranted when comparing our study with previous works targeting movement disorders due to an organic disease (e.g., hemiplegia).…”

“…More precisely, patients with impaired movement execution due to various different causes, including dystonia (Fiorio et al, 2011), spinal cord injury (Lenggenhager et al, 2012; Scandola et al, 2014; Tidoni et al, 2014) or stroke (Burin et al, 2015), present with a weaker sense of body ownership. Furthermore, a recent TMS study in healthy participants showed that excitability of the primary motor cortex interacts with body ownership (Della Gatta et al, 2016).…”

The Embodiment of Objects: Review, Analysis, and Future Directions

“…This network includes an important area for the interaction between affective embodiment and motor system, the ventral premotor cortex (Ehrsson et al, 2004;Makin et al, 2008b;Blanke et al, 2015). Also, spinal cord injuries have been shown to have an altered sense of body ownership (Scandola et al, 2014).…”