The effect of space missions on gravity-responsive torsional eye movements.

Three astronauts underwent preflight, inflight, and postflight testing of spontaneous ocular torsion and of ocular counterrolling (OCR), reflexes governed by the gravity-responsive otolith organs in the inner ear. One astronaut, A, had a 30-day space mission on Euromir '94 and was examined monocularly with SensoMotoric Instruments video-oculography (VOG). The other two astronauts, B and C, were studied with a binocular VOG and flew an 180-day mission on Euromir '95. In space, spontaneous eye torsion in the upright position was found to be substantially offset from baseline Earth-based recordings in all three subjects for the duration of the flights. In addition, the binocular studies showed a marked torsional disconjugacy. On return to Earth, offset and torsional disconjugacy persisted for many days. OCR in response to 30 degrees right and left tilt was examined preflight and postflight. Compared to preflight, Astronaut A showed reduced OCR immediately postflight, which increased over the next few days. Both Astronauts B and C had increased OCR postflight, which gradually approached but did not achieve the preflight values over 13 days postflight. The adaptation of ocular torsion in space in one astronaut and not in the other two, and slow adaptation postflight, may reflect the lack of visual feed-back and the open loop nature of the otolith-ocular torsion reflex.

[1]  I. Curthoys,et al.  Convergence of labyrinthine influences on units in the vestibular nuclei of the cat. II. Electrical stimulation. , 1971, Brain research.

[2]  H Mittelstaedt,et al.  The influence of otoliths and somatic graviceptors on angular velocity estimation. , 1996, Journal of vestibular research : equilibrium & orientation.

[3]  S. Diamond,et al.  Vestibular involvement in spasmodic torticollis: an old hypothesis with new data from otolith testing. , 1988, Advances in oto-rhino-laryngology.

[4]  Wang Lj,et al.  Ocular counterrolling as an indicator of vestibular otolith function , 1999 .

[5]  E I Matsnev,et al.  Space motion sickness: phenomenology, countermeasures, and mechanisms. , 1983, Aviation, space, and environmental medicine.

[6]  S. Kompanejetz.  On compensatory Eye movements in Deaf-mutes , 1925 .

[7]  B. Cohen,et al.  Sensing and Controlling Motion: Vestibular and Sensorimotor Function (Annals of the New York Academy of Sciences, Volume 656) , 1992 .

[8]  T Vilis,et al.  A reexamination of the gain of the vestibuloocular reflex. , 1986, Journal of neurophysiology.

[9]  B Cohen,et al.  Labyrinthine and extra-labyrinthine effects on ocular counter-rolling. , 1971, Acta oto-laryngologica.

[10]  H Mittelstaedt,et al.  Somatic versus Vestibular Gravity Reception in Man , 1992, Annals of the New York Academy of Sciences.

[11]  S G Diamond,et al.  Ocular counterrolling abnormalities in spasmodic torticollis. , 1988, Archives of neurology.

[12]  R. Tomlinson,et al.  Behavior of cells without eye movement sensitivity in the vestibular nuclei during combined rotational and translational stimuli. , 1996, Journal of vestibular research : equilibrium & orientation.

[13]  A H Clarke,et al.  Evaluation of the torsional VOR in weightlessness. , 1993, Journal of vestibular research : equilibrium & orientation.

[14]  S G Diamond,et al.  Binocular Counterrolling during Sustained Body Tilt in Normal Humans and in a Patient with Unilateral Vestibular Nerve Section , 1982, The Annals of otology, rhinology, and laryngology.

[15]  S G Diamond,et al.  Further evidence to support disconjugate eye torsion as a predictor of space motion sickness. , 1992, Aviation, space, and environmental medicine.

[16]  R D Tomlinson,et al.  Eye position signals in the vestibular nuclei: consequences for models of integrator function. , 1994, Journal of vestibular research : equilibrium & orientation.

[17]  G. I. Samarin,et al.  [Interlabyrinthine asymmetry, vestibular dysfunction and space motion sickness]. , 1986, Kosmicheskaia biologiia i aviakosmicheskaia meditsina.

[18]  W Bles,et al.  Ocular rotation and perception of the horizontal under static tilt conditions in patients without labyrinthine function. , 1991, Acta oto-laryngologica.

[19]  I S Curthoys,et al.  Convergence of labyrinthine influences on units in the vestibular nuclei of the cat. I. Natural stimulation. , 1971, Brain research.

[20]  S G Diamond,et al.  Prediction of space motion sickness susceptibility by disconjugate eye torsion in parabolic flight. , 1991, Aviation, space, and environmental medicine.

[21]  S G Diamond,et al.  Ocular torsion in upright and tilted positions during hypo- and hypergravity of parabolic flight. , 1988, Aviation, space, and environmental medicine.

[22]  A H Clarke,et al.  A compact equipment package for vestibular experiments during spaceflight. , 1991, Acta astronautica.