Fig. 1
Visual stimulation in the visual and visuo-vestibular sessions consisted of three superimposed layers, oriented perpendicular to the subject’s antero-posterior axis from back to front (see Methods). Layer 0 comprised the background of the virtual scene. Layer 1, positioned immediately in front of Layer 0, contained the visual target, a grey-textured disk with a diameter of 1.68° of visual angle. Located in front of Layer 1, Layer 2 included two elements: a uniformly colored surface with a central circular aperture; and a black cross tilted by 45° at its center. In Layer 1 and Layer 2, transparent portions of the scenario are represented with a squared texture. The resulting 3D virtual scenario was perceived by the subject through the VR-headset system (see also Supplementary Video 1 and Supplementary Video 3). In the vestibular session, visual stimulation consisted solely of the background (Layer 0; see also Supplementary Video 2). The WRF (axes x, y, z, represented in red in the figure) has its origin in the flying base motion centroid position when the flying base is in its home settled position. Motion centroid is the centroid of the joints below the flying base of the motion platform. The z-axis is orthogonal to the ground and oriented upwards. The x-axis is oriented along the posterior-anterior direction of the chair.
