Figure 2

Experiment 3: conditions and results.

(a) Experimental conditions for Experiment 3. Participants were seated in the rotating chair wearing a head-mounted display showing (or not) a pattern of moving dots. Participants were asked to detect faint tactile stimuli delivered to their right or left index fingers (black colour indicates stimulus present). Three conditions were tested: no rotation baseline (B), vestibular only condition (Ve, passive whole-body rotations at 90°/s) and visuo-vestibular condition (Vi+Ve, passive whole-body rotation at 90°/s associated with speed incongruent optic flow at 10°/s). (b) Experimental hypothesis. If the influence of vestibular signals on tactile sensitivity is a direct product of the activation of the vestibular projections, data should show an increase in somatosensory sensitivity in both Ve and Vi + Ve conditions (independent modulation hypothesis). Conversely, if somatosensory sensitivity is affected by integrated visual and vestibular signals leading to the perception of slower speed, tactile enhancement should be reduced in the Vi + Ve condition, relative to Vi (visuo-vestibular-somatosensory interaction). (c) Sensitivity (d’) and response bias (C) data as a function of experimental condition. Results show higher sensitivity in the vestibular only condition as opposed to the baseline and visuo-vestibular conditions. No difference was found between the latter two. There were no significant differences in response bias. Error bars represent the standard error.