Figure 1. Experimental stimuli, setup, and procedure.

(A) Visual stimuli showing a virtual body in prone posture from an elevated downward perspective used during the strong Visuo-Vestibular Conflict condition (left panel) and the same body standing used during the weak Visuo-Vestibular Conflict condition (right panel). Visual implied direction of gravity in each panel is indicated by a white arrow and ‘g*’ label. Visual stroking was presented by red dots (trajectory indicated by black arrows). (B) Participant lying supine, equipped with a ball to facilitate mental imagery during Mental Ball Dropping task, a button response device, and a head-mounted display. Direction of veridical vertical is indicated by a white arrow and ‘g’ label. (C) Robotic device used for tactile stimulation of the participants’ back. Stroking units (in red color) were actuated by ultrasonic motors. (D) Sequence of events in an experimental trial.