This project proposes to test the effect of immersion in a tilted virtual reality on verticality representation in hemisphere stroke patients showing lateropulsion and in healthy participants. The idea is to use the virtual reality as a tool to recalibrate the internal reference of verticality (contralesionally biased) in stroke patients and to experimentally create a bias in verticality perception of healthy participants, then to investigate how this modulation of the internal model of verticality might affect the erect posture. The investigators hypothesize that, in stroke patients, the recalibration of the verticality perception might ameliorate their lateropulsion, whereas in healthy participants, the experimental verticality bias introduced might induce a transient experimental lateropulsion. A transmodal modulation of the verticality perception, both on PV and VV, would imply a modulation by the virtual reality not only at the level of perception but also at the internal model of verticality, advocating for a powerful effect of this technology. The analysis of a post-effect (on verticality perception) that would continue after the intervention (immersion in the virtual titled room) would be a supplementary argument advocating for its clinical use in rehabilitation of post-stroke lateropulsion. To judge the effect of the immersion in tilted virtual reality, the following measures will be considered: (a) PV perception, (b) VV perception, (c) body orientation measured by inertial captors, and (d) weight-bearing asymmetry in erect posture assessed by posturography.
VIRGIL is a monocentric interventional study aiming to investigate the effect of immersion in a virtual tilted room on modulation of the verticality representation (postural vertical [PV] and visual vertical [VV]), which in turn might affect body orientation (head and trunk). To this end, the investigators will conduct a within-person randomized trial including post-stroke patients and healthy participants.