Sleep Deprivation Does Not Affect Vestibulo-Ocular Reflex Gain but Deteriorates Vestibular Adaptation Ability?

Objectives: To assess the effect of acute sleep deprivation on the physiologic, adaptive, and behavioral properties of vestibulo-ocular reflex (VOR) compared with a full night's sleep. Design: Seventeen volunteers (age range 32 to 42 years, 7 females) were recruited into this crossover study and evaluated for 2 nights, first after normal sleep, and then after 24 hours of sleep deprivation. Tests included physiological VOR assessments by means of the Video Head Impulse Test in four random conditions consisting of far and near targets and performed with active (self-induced) and passive head movements. The adaptation ratio was calculated as the amount of change between VOR gains in near- and far-target conditions (near-VOR gain/far-VOR gain × 100). Behavioral VOR was evaluated by a computerized dynamic visual acuity test. Results: Fourteen participants completed the protocol (age range 34 to 42 years, 5 females). The VOR gain did not change following sleep deprivation for the passive head rotations or any of the tested conditions (paired t test >0.05). The VOR gain increased significantly in the middle of the night during the sleep deprivation: far-target-passive impulse (analysis of variance [ANOVA] F = 8.67, p = 0.001, 9 p.m. to 2 a.m. p = 0.001 post hoc); near-target active-impulse (ANOVA F = 4.66, p = 0.019, 2 a.m. to 6 a.m. p = 0.021 post hoc). The magnitude of VOR gain adaptation significantly reduced 7.1% after sleep deprivation for active head rotation (repeated measure ANOVA F = 5.212, p = 0.013). Measures of the behavioral VOR (difference between static and dynamic visual acuity) was not different between conditions (Wilcoxon signed-rank test, p value >0.05). Conclusion: Sleep deprivation reduced adaptative capacity of the VOR gain without affecting the physiologic or behavioral function of the VOR. The increase in VOR gain during the night might be explained by circadian rhythm involvement.