Simulator Adaptation Syndrome (SAS) and the Vestibular System: An Exploratory Study

Driving simulators are increasingly being used for the evaluation and rehabilitation of fitness-to-drive. However, difficulties with Simulator Adaptation Syndrome (SAS) are commonly reported in the literature. In this study, the authors investigated the relationship between SAS and incongruences between vestibular and visual inputs. Fifteen individuals (age = 61±13 years, 9 females) who developed SAS (SAS+) and 10 individuals (age = 58±13 years, 4 females) who did not develop SAS (SAS-) during two recently completed simulator-based driving studies participated in this study. Participants were each administered the six conditions of the Sensory Organization Test (SOT), made to rest for 30 minutes, and then drove four Wii®-based programs. Performance on the six SOT conditions and on the four the Wii®-based driving programs by SAS+ participants were compared to those of the SAS- participants. No participant reported feeling sick during the SOT. Participants in the SAS+ group performed better (p = 0.0053) than those in the SAS- group only on the SOT fifth condition, which required reliance on vestibular input for maintaining balance control. Four participants in the SAS+ versus one in the SAS- group experienced SAS during the Wii®-based driving (chi-square = 4.63, p = .0314). The results of the study suggest that individuals who developed SAS in the driving simulator probably relied more heavily on their vestibular system than individuals who did not develop SAS, and thus performed better when in situations that required significant integration of vestibular input for maintenance of equilibrium. The independent effect of the driving simulator versus the Wii driving game also suggests that specific characteristics of simulator environment immersion also likely played a role in eliciting SAS. Individuals who rely heavily on their vestibular system for balance control may be more prone to developing SAS in virtual environments that provide only minimal vestibular feedback. More studies are needed to better understand SAS and develop more effective strategies to mitigate it.