INVESTIGATING THE ALTERATIONS OF BODILY SELF-CONSCIOUSNESS IN SPINAL CORD INJURY WITH THE REAL LEG ILLUSION: AN FMRI STUDY

The sense of one's own body, also called bodily self-consciousness (BSC), mediates our interactions with the environment. Traditionally, it has been investigated via multisensory manipulations, such as the rubber hand illusion (RHI). Importantly, even though BSC is often altered in clinical conditions such as spinal cord injury (SCI), impacting the daily life of individuals, its underlying mechanisms are still poorly understood. Here, we investigated behavioral and neural correlates of BSC in individuals with and without SCI with a fMRI experiment employing a multisensory stimulation paradigm based on the RHI.
Seventeen individuals with SCI (12M; age: 45.9±15.1) and 14 without (9M; age: 46.4±14.5) underwent the fMRI experiment in which tactile stimulation was applied to their legs, while they observed a pair of virtual legs being stroked. Positional congruency (congruent/incongruent) and temporal alignment (synchronous/asynchronous) between the seen and felt touch was modulated. After each condition, the participants reported the perceived strength of the illusion (SoI).
Behaviorally, we observed a significant group-stimulation synchronicity interaction on the SoI (p<0.001). Post-hoc tests revealed a significant between-group difference in the SoI in asynchronous conditions (SCI group perceived a stronger illusion, p<0.05). Preliminary fMRI analyses suggest group-and synchronicity-dependent activations in the left middle frontal and supramarginal gyri, extrastriate body area and the bilateral supplementary motor area.
These findings suggest that the timing of stimulation is the main contributor to the illusion, with emerging group-based differences. The results will be used to perform further imaging investigations, to provide a neural framework for altered BSC after SCI.