Optokinetic nystagmus,vection, and motion sickness

BACKGROUND: Two current theories concerning the etiology of motion sickness (MS)-the eye movement hypothesis and sensory conflict theory-were evaluated under conditions that manipulated the degree of optokinetic nystagmus (OKN) and/or vection. METHOD: Eye movement and perceptual responses were elicited with whole field stimulation in a vertically striped rotating drum and modulated with fixation and/or a restriction of the field of view (FOV). Measures of OKN, vection, and MS were recorded under the various conditions. RESULTS: Both visual field restriction and/or fixation diminished circular vection, OKN, and MS. Conditions involving both fixation and restricted FOV resulted in greater reductions in MS than did either restriction alone. CONCLUSIONS: These findings lend support to a multi-factor explanation of MS, involving both sensory conflict and eye movement.