VIrtual Reality Glasses Use to Improve Lateropulsion and the Post-stroke Postural Vertical

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.

• Changes in the visual perception of the vertical (VV) before and during the immersion in a virtual tilted room, in stroke and healthy participants. [Time frame: Days 1 and 3 if assignment to plane A or days 2 and 4 if assignment to plane B of the W2]
• Post-effect on PV. Change from baseline in PV orientation that continues after the immersion in virtual reality, in stroke and healthy participants. [Time frame: Days 1 and 3 if assignment to plane A or days 2 and 4 if assignment to plane B of the W2]
• Post-effect on VV. Change from baseline in VV orientation that continues after the immersion in virtual reality, in stroke and healthy participants. [Time frame: Days 1 and 3 if assignment to plane A or days 2 and 4 if assignment to plane B of the W2]
• Modulation of active vertical trunk orientation. Change from baseline in active vertical trunk orientation assessed by inertial captors during the modulation of the internal model of verticality by virtual reality, in stroke and healthy participants. [Time frame: Days 2 and 4 if assignment to plane A or days 1 and 3 if assignment to plane B of the W2]
• Modulation of active vertical pelvis orientation. Change from baseline in active vertical trunk orientation assessed by inertial captors during the modulation of the internal model of verticality by virtual reality, in stroke and healthy participants. [Time frame: Days 2 and 4 if assignment to plane A or days 1 and 3 if assignment to plane B of the W2]
• Modulation of active vertical head orientation. Change from baseline in active vertical head orientation assessed by inertial captors during the modulation of the internal model of verticality by virtual reality, in stroke and healthy participants. [Time frame: Days 2 and 4 if assignment to plane A or days 1 and 3 if assignment to plane B of the W2]
• Effect on lateropulsion. Change from baseline in lateropulsion scores assessed by the SCAle for LAteropulsion after 4 consecutive half days of verticality referential recalibration by virtual reality, in stroke participants. [Time frame: 45 minutes every Friday during the protocol (W0, W1, W2, W3).]
• Effect on postural capacities. Change from baseline in balance scores assessed by the modified Postural Assessment Scale for Stroke patient after 4 consecutive half days of verticality referential recalibration by virtual reality, in stroke participants [Time frame: 45 minutes every Friday during the protocol (W0, W1, W2, W3).]
• Responders to virtual reality. Proportion of participants in whom the immersion in a virtual tilted room modulates PV (at least 2 degrees). [Time frame: Days 1 and 3 if assignment to plane A or days 2 and 4 if assignment to plane B of the W2]
• Changes in weight-bearing asymmetry. Evaluation of changes in weight-bearing asymmetry in standing posture before and during the immersion in a virtual tilted room, in stroke and healthy participants. [Time frame: Days 2 and 4 if assignment to plane A or days 1 and 3 if assignment to plane B of the W2]
• Awareness of the changes in active vertical body orientation. Evaluation of participants' awareness of the changes in body orientation and balance in standing posture induced by virtual reality. [Time frame: Days 2 and 4 if assignment to plane A or days 1 and 3 if assignment to plane B of the W2]
• Relationship between the trunk tilt (assessed by inertial captors, in degrees) and the weight bearing on the paretic side (in percentage of body weight), at baseline, with average values (2 sessions) [Time frame: Days 2 and 4 if assignment to plane A or days 1 and 3 if assignment to plane B of the W2]