Vestibular function and sensory interaction in space flight.

The vestibular system and vestibulo-visual interaction were examined in 11 astronauts by the electrooculographic (EOG) method during short- and long-term flights on days 2, 3, 5, 9, 22, 50, 164, and 169 (experiments OPTOKINES and LABYRINTH). In space (flight days 2 and 3), they showed enhanced spontaneous vertical nystagmus, and disorders of tracking of vertical and diagonal movements of the stimulus which improved after active head movements. Early increasing of the reactivity of the cupulo-endolymphatic system (flight days 2-3) was replaced after 5 days of flight with a reduction of the vestibular function and an increase of the significance of the visual input in the formation of oculomotor responses to combined vestibulo-optokinetic stimulation. The type of spontaneous ocular reaction and vestibular stimulation of oculomotor activity under the conditions of weightlessness represented, on one hand, the general responses of sensory systems to weightlessness and, on the other hand, specificity of integrating and adaptive processes.