adaptation to spaceflight and periodically during prolonged flight, the system of smooth visual
tracking was found to undergo a transition to a strategy of saccadic approximation (abrupt
rapid movements of both eyes). These impairments, seen in virtually all the crew members,
were apparently due to vestibular deprivation in space.
Pre and postflight examinations of 9 cosmonauts participating in ISS missions were completed
using a computer-aided method to investigate eye motion control and vestibular function after
long-term stay in microgravity (126-195 days). Studies of the vestibular function, intersensory
interactions, and the tracking function of the eyes in the crew members were performed on
days 1-2, 4-5, and 8-9 after return to Earth. The role and significance of the vestibular system
(the vestibule and semicircular canals of the inner ear and the vestibulocochlear nerve that
work with the brain to maintain balance and orientation) in eye tracking were determined.
Results of the postflight examinations showed a significant change in the accuracy, velocity, and
temporal characteristics of eye tracking and the muting of the vestibular response. Although,
microgravity does not directly influence visual functions, changing the level and pattern of inner
ear sensory/receptor input leads to a decrease in the accuracy and velocity of all forms of visual
tracking. Eye destabilization related to an increase in slow drift, the appearance of a great
number of saccadic (abrupt fast) movements, and the emergence of spontaneous nystagmus
(involuntary eye movement) was found. Similar disturbances, as those previously seen during
flight, in the accuracy of saccadic and smooth tracking (especially in the vertical plane) and the
development of a new tracking strategy (the gaze approaches a target and follows its
movement using a set of saccadic movements) were demonstrated and lead to a considerable
increase (by a factor of three or more) in the time required for examining and identifying a
target and setting the gaze on targets post landing. In the selected period of examination (9
days after the flight), no recovery of the indices of the tracking eye function to the baseline
level was observed; however, a tendency for normalization was recorded.
PUBLICATION(S)
Clarke AH, Just K, Krzok W, Schonfeld U. Listing’s plane and the 3D-VOR in microgravity--the
role of the otolith afferences. Journal of Vestibular Research. January 1, 2013;23(2):61-70. doi:
10.3233/VES-130476.
Clarke AH, Kornilova LN. Ocular torsion response to active head-roll movement under one-g
and zero-g conditions. Journal of Vestibular Research. 2007;17(2-3):99-111.
Kornilova LN, Alekhina MI, Temnikova VV, et al. The effect of a long stay under microgravity on
the vestibular function and tracking eye movements. Human Physiology. 2006;32(5):547-555.
doi: 10.1134/S0362119706050082.
Kornilova LN. The role of gravitation-dependent systems in visual tracking. Neuroscience and
Behavioral Physiology. 2004;34(8):773-781. doi: 10.1023/B:NEAB.0000038127.59317.c7.
This investigation is complete and all results are published.