Adaptation of the horizontal vestibuloocular reflex in pilots.

OBJECTIVES/HYPOTHESIS: The vestibular function in pilots has been reported as being different to that in other, normal subjects. However, there is little evidence as to why and when this occurs, and its cause is still in doubt. The aim of this study was to evaluate changes in vestibular function in student pilots attending an elementary flight course, and in other active pilots, through the use of the slow harmonic acceleration (SHA) test and to verify the occurrence and timing of any vestibular function changes.

STUDY DESIGN: Cross-sectional and prospective group design.

METHODS: The six study groups were control, student pilots before and after flight training, and three groups of active pilots classified according to flight time. Gain, phase, and symmetry of horizontal eye movements induced by sinusoidal harmonic acceleration test were investigated.

RESULTS: There were significantly higher gain values in all active pilot groups as compared with the control group at frequencies above 0.04 Hz, and in student pilots after flight training, as compared with before training at 0.01, 0.04, and 0.08 Hz. However, there were no significant differences in gain values among the three groups of active pilots or between gain values in student pilots before flight training and those of the control group. We could not find any reliable relationship between vestibuloocular reflex (VOR) function changes and other factors such as age, height, and weight.

CONCLUSIONS: We suggest that these results might be explained by adaptations caused by VOR plasticity rather than habituation and that flight training might be responsible for the modulation of the vestibular function in pilots.