How active head movement and fixation type modulate the brain's ability to detect mismatches between visual and vestibular signals
Stable perception of a visual environment depends on the brain's ability to compare and evaluate the congruence of visual and vestibular signals. When these signals mismatch as in simulator sickness, vertigo, or motion sickness the consequences can be significant. Prior work suggested that sensitivity to visual-vestibular conflict is modulated by fixation type, with eye movement signals playing an important role. This research project investigated whether active head movement signals, specifically neck motor commands and proprioception, also modulate conflict detection, and whether the type of visual fixation (head-fixed vs. scene-fixed) interacts with this.
16 healthy adults completed a two-alternative forced-choice task in which head movement was eather self-generated or externally driven, and visual fixation was either head-fixed or scene-fixed. Participants viewed a starfield stimulus in a virtual reality head-mounted display and judged whether the visual scene moved with or against their head motion across trials.
Active head movement with scene-fixed fixation produced the best conflict detection. Scene-fixed fixation significantly improved precision relative to head-fixed fixation, and active movement showed a significant effect on conflict sensitivity. These findings suggest conflict detection is modulated by motor commands, including eye and head movement efference copies. Scene-fixed fixation likely reduces retinal image motion velocity, while active movement increases precision in head movement estimation.
Poster presented at the Vision Sciences Society 19th Annual Meeting, May 2019.