Abstract
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Background: Sensory conflict may be a factor in simulator sickness
(SS) given that visual input is often inconsistent with other sensory
inputs. It was predicted that an expanding optical flow pattern would
lead to more sensory conflict, and subsequently more SS than a contracting
pattern. Methods: There were 16 individuals who participated
in the experiment (6 men, 10 women, mean age 24.4 yrs). Subjects
viewed a steadily expanding pattern of blue squares displayed on a
computer monitor. In a second condition the pattern steadily contracted.
Subjects completed the Simulator Sickness Questionnaire (SSQ) designed
by Kennedy and colleagues both before and after a trial (5 min
exposure to optic flow). A total SSQ score and three SSQ sub-scores
(nausea, oculomotor, and disorientation) were obtained. Results: Mean
post-treatment total SSQ scores (mean 28) in the expanding condition
were higher than those obtained in the contracting condition (mean
17). Nausea and oculomotor SSQ sub-scores were also higher in the
expanding condition compared with the contracting condition. Conclusions:
Experience with expanding flow patterns that result during forward
self-motion, and the sensory inputs that usually accompany them,
have resulted in a central nervous system expectancy about what the
appropriate inputs should be during forward self-motion. Less experience
with backwards self-motion (and contracting patterns) may result
in a lower level of expectation regarding what the appropriate sensory
inputs should be for contracting flow patterns. This lower level of neural
expectancy may subsequently lead to less sensory conflict and less SS
generated by contracting flow patterns.