Comparison of optokinetic scene effects on the somatogyral illusion.
The objective of this study was to determine during rotation the relative importance of a scene in achieving "visual dominance" over non-visual vestibular orientation inputs, e.g., otolith and semicircular canals. Five visual scenes were presented, while rotating the subject (at three angular acceleration rates), to obtain the vestibular and optokinetic nystagmus and perception of rotation. The onset time and direction of rotation, as well as EOG and chair velocity were recorded. Adaptation times during rotation at constant angular velocity and during post-rotation were also recorded. Analysis of perceived times (onset, adaptation, and post-rotatory adaptation) with the EOG slow-phase velocity at respectively perceived times were analyzed using the SAS procedures Analysis of Variance (ANOVA) and General Linear Models (GLM). Basic hypotheses for the study were: "There are no differences in latencies for either onset time (L1), adaptation to rotation (L2), or adaptation to post rotatory motion (L4), between treatment conditions, or between Groups of subjects, or between acceleration rates, between constant rotation velocities, or between direction of rotation." From the results, it was concluded that pilots are highly visually dependent; additionally, if there is a sensory conflict, a larger percentage of individuals (pilots) will follow visual perceptions even if the demands of the aerial environment and our perception is incorrect. However, in sensory conflict conditions, with degraded visual scene individuals including pilots will revert to vestibular perception rather than visual perception (less visually coupled), approaching percentages as noted with a dark environment.