Article

The study aimed at inducing a visual vertical (VV) bias
by immersion in a virtual tilted room (VTR, visual cues), then testing the effect
of 30% body-weight support walking (BWSW, somaesthetic cues) to correct this
bias. METHODS: We included 20 healthy participants (median age 54 years; 12
females) who wore the Oculus-Rift((R)) Head Mounted Display to produce the
virtual reality and generate the VV. VV (8 trials) was tested at baseline, then
in 3 postural conditions (walking, sitting and BWSW), by 2 visual conditions
(darkness and VTR), according to a pseudo-randomized blocked design. The VTR was
tilted 18 degrees clockwise. Data for 3 participants with virtual reality
sickness were discarded, and those for 17 participants underwent non-parametric
statistical analysis by 2 main criteria: VV and head orientation. RESULTS: The
VTR induced a pronounced tilt of the vertical toward the tilted side under the
baseline condition (median 11.4 degrees [Q1-Q3 6.1-13.4]; P<0.01), with a large
effect size (r=0.88). The effect was systematic, with great inter-individual
variability (2-17 degrees ), and was similar under every postural condition
(P<0.001), with a post-effect lasting 6min and suppressed under BWSW. In
darkness, VV was more upright during BWSW than sitting (P<0.05), with a medium
effect size (r=0.49). The VTR induced a slight head tilt of median 3.3 degrees
[2.8-5.9] toward the tilted side under every postural condition (P<0.001), with a
large effect size (r=0.87). In darkness, the head was upright only at baseline
and under BWSW. CONCLUSION: Being immersed in a tilted environment induces a
powerful bias in verticality perception (11 degrees ). Contrary to our
hypothesis, BWSW did not attenuate the effect induced by the VTR, probably
because of the power of this effect. However, BWSW was the only postural
condition able to suppress post-effects induced by the VTR, thereby leading to
the head and VV oriented upright. BWSW may improve verticality representation,
presumably by bringing augmented information about the direction of the Earth
vertical. These findings represent an avenue for rehabilitation of patients with
postural disorders caused by a wrong verticality representation. Technological
improvements will be necessary to attenuate the virtual reality discomfort.
CI - Copyright (c) 2018. Published by Elsevier Masson SAS.
- Réalité virtuelle

Langue : ANGLAIS