Visuo-motor and interoceptive influences on peripersonal space representation following spinal cord injury.

Peripersonal space (PPS) representation is affected by information coming from body, as demonstrated by patients with spinal cord injury (SCI) in whom a body-brain disconnection leads to deafferentation and deefferentation of the below-lesion body parts. In particular, in paraplegic individuals whose lower limb sensory-motor functions are impaired or completely lost, the representation of PPS around the feet is reduced. However, passive motion can have short-term restorative effects. What remains unclear is the mechanisms underlying this recovery and in particular the contribution of visual and motor feedback and of interoception. Using virtual reality technology, we dissociated the motor and visual feedback during passive motion in paraplegics with complete and incomplete lesions and in healthy controls.Results show that in the case of paraplegics (even those with complete lesions), the presence of motor feedback is necessary for the recovery of PPS representation, both when the motor feedback is congruent and incongruent with the visual one. In contrast, visuo-motor incongruence leads to inhibition of the PPS representation in controls.There were no differences in sympathetic responses between the three groups. Nevertheless, in individuals with incomplete lesions, greater interoceptive sensitivity is associated with better representation of PPS around the feet in visuo-motor incongruent conditions.These results shed new light on the modulation of PPS representation, and demonstrates the importance of residual motor feedback and its integration with other bodily information in maintaining space representation.