[Effect of altered blood circulation on human nystagmic reactions]

Optokinetic and vestibulo-optokinetic nystagmus in response to optokinetic and combined vestibulo-optokinetic stimulation applied during head-down tilt was investigated. Tilt-induced circulation changes produced a modifying effect on nystagmic reactions which included a decrease of optokinetic and vestibulo-optokinetic nystagmus and its subsequent recovery after return to the horizontal position. The absolute parameters of vestibulo-optokinetic nystagmus changed depending on the direction of head movements in the sagittal plane relative to the long axis of the body. Some aspects of the relationships between sensory and nystagmic components of vestibular reactions during "conflict" stimulation of the vestibular and visual sensory systems are discussed.