Optokinetic stimulation in microgravity: torsional eye movements and subjective visual vertical.

Introduction: Microgravity provides unique sensory inputs to the vestibular and oculomotor systems. We sought to determine the effects of long-term spaceflight on sensing of spatial orientation.

Methods: Two cosmonauts participated in experiments on human vestibulo-visual interactions during a long-term mission (178 d) in the MIR station in 1995.