MOP / SICSAS

Abstract: During the first days in space 50-80 % of the astro- and cosmonauts suffer from the Space Adaptation Syndrome (SAS). European scientist astronauts of the D1 Spacelab Mission mentioned close similarities between the symptoms of  SAS and the symptoms they experienced after a 3G centrifuge run on earth (Sickness Induced by Centrifugation, SIC). The hypothesis that susceptibility to SAS correlates with susceptibility to SIC was investigated during the Euromir ’94 mission and will be elaborated further during the 2004 DELTA Mission. This is of interest since a correlation implicates a general vestibu­lar adaptation mechanism to changing G-levels. The vestibular adaptation to gravity transitions forms the focus of the current experiments. Susceptibility to SIC will be assessed after a 1 hour 3Gx centrifuge run, the susceptibility to SAS and vestibular adaptation process will be the focus of the inflight experiment.

Address corresponding author:
Dr. Jelte E. Bos (PI), TNO-Human Factors, Kampweg 5, 3769 DE Soesterberg, P.O. Box 23, 3769 ZG Soesterberg, The Netherlands
phone: +31 (0)346 356 371, fax:+31 (0)346 353 977, email: bos@tm.tno.nl

Co-Investigators (all TNO-Human Factors):
Suzanne A.E. Nooy, Dr. Eric L. Groen (see his academic thesis), Dr. Willem Bles, Dr. Ries Simons.

Introduction: During the first days in space 50-80 % of the astro- and cosmonauts suffer from the Space Adaptation Syndrome (SAS). Although it is generally agreed that the vestibular system is involved in the underlying mechanism causing the Space Adaptation Syndrome (SAS), no distinct clue has been found to the aetiology of SAS or the individual susceptibility and predictability. The symptoms of SAS, like nausea and dizziness, are especially provoked by head movements, and hamper the astronaut’s functioning to large extent. It normally takes two or three days to adapt to the new gravitational environment (Locker, 2003). Although the symptoms of SAS are similar to symptoms of motion sickness on earth (MS), susceptibility to SAS does not correlate with susceptibility to MS. However, susceptibility to SAS seems to correlate with susceptibility to Sickness Induced by Centrifugation (SIC). SIC may occur after exposure to a level of 3G for a period of 1 hour in a human centrifuge. European scientist astronauts of the D1 Spacelab Mission mentioned close similarities between the symptoms they experienced after a 3G centrifuge run and those of SAS. This suggests that a gravity transition from 3 to 1 G provokes the same effects as a transition from 1 to zero-G. Since previous experiments regarding SIC showed that a change in the orientation of the head relative to the gravity vector is provocative, it is concluded that gravity as sensed by the vestibular system plays a key role in the generation of SIC and, thus, of SAS. To investigate whether susceptibility to SAS correlates with susceptibility to this Sickness Induced by Centrifugation (SIC), we previously performed an experiment during the EUROMIR Mission of 1994. The 2004 DELTA Mission to ISS gives us the opportunity to further elaborate our hypothesis concerning the correlation between SIC and SAS. This is of interest since a correlation implicates a general vestibu­lar adaptation mechanism to changing G-levels. The vestibular adaptation to gravity transitions forms the focus of the current experiment.

Objectives: The main objective of this study is to obtain insight in the process of vestibular adaptation to G-transitions. Two important parameters are the perception of body motion and attitude during the adaptation process. A second objective is to investigate the correlation between susceptibility to SAS and to SIC.

Methods: To meet the two aforementioned objectives, this study consists of a one day ground based experiment for each subject participating, carried out 2-6 months pre-flight, and an in-flight experiment. In the ground experiment, the astronauts’ susceptibility to SIC will be assessed after exposure to hypergravity in a human centrifuge. Because the  (duration=1 h, load=3 Gx). Their vestibular function will be examined before and after the centrifuge run by rating the motion perception characteristics induced by head movements in different body postures, by stabilometry in a tilting room and by subjective vertical and eye movement registrations. Based on the cosmonauts’ susceptibility to SIC, we will make a prediction about their susceptibility to SAS.
During the in-flight experiment, astronauts are asked to fill in a short questionnaire, wherein they report their motion sensation as a result of head movements, and whether they experience any discomfort regarding SAS caused by their daily activities. Emphasis will lie on the effect of head movements around the three principal axes. Reporting will take 5 min a day, during a period from 2 days before launch until 14 days after landing.

Previous experience: Previous experiments concerning SIC and SAS were conducted with the astronauts of the D1 Spacelab Mission, and of the EUROMIR’94 mission. Of the eight astro- and cosmonauts that participated in these experiments, the ones that were susceptible to SIC were also susceptible to SAS, and the ones that were not affected by the long duration centrifugation appeared to be unsusceptible to SAS. These results underscore our hypothesis, that there is a positive correlation between SIC and SAS. Long duration centrifugation experiments were also performed with many subjects without space experience (»40)

New information expected: The present experiment is planned to validate the earlier results with the D1-and EUROMIR European astronauts, enlarging our sample of subjects to correlate the susceptibility to SAS with the susceptibility to SIC. A correlation between SIC and SAS may suggest that these phenomena share the same underlying mechanism, which would make SIC a valuable tool for examining SAS on earth. During the ground experiment wherein the astronauts’ susceptibility to SIC will be assessed, we focus on the determination of (physiological) parameters that play a key role in vestibular adaptation and that might be indicative for susceptibility to SAS.

Research facilities used in these experiments:

TNO rotation chair: able to combine vestibular stimuli (tilt and/or rotation) with visual stimuli (optic flow in roll). Used for addressing motion and attitude perception.

See how this looks like. (1.6 Mb movie)

TNO Tilting Room: Assessment of postural stability.

Video Oculo Graphy: 3D eye movement recordings (Eye Tracker device, Chronos Vision, GmbH, Germany)

Human Centrifuge: located at the ‘Centrum for Mens en Luchtvaart’ (CML), Soesterberg, The Netherlands. Click for details on this particular centrifuge.

Related articles:

• Bles, W., Bos,J.E., Furrer, R., de Graaf, B., Hosman, R.J.­A.W., Kort­schot, H.W., Krol, J.R., Kuipers, A., Marcus, J.T., Messerschmid, E., Ockels, W.J., Oosterveld, W.J., Smit, J., Wertheim, A.H. and Wientjes, C.J.E. (1989) Space Adaptation Syndrome induced by a long duration +3Gx centri­fu­ge run. Report TNO-IZF 1989-25.
• Bles W and de Graaf B. (1993) Postural consequences of long duration centrifugation. Journal of Vestibular Research Vol 3, No. 1, pp. 87-95
• Bles, W. and van Raaij, J.L. (1988) The tilting room and the spacelab D1 mission. Adv. ORL., vol 42, 13-17.
• Bles, W. and van Raaij, J.L. (1988) Pre- and Postflight Postural Control of the D1 Spacelab Mission Astronauts examined with a Tilting Room. Report TNO-IZF 1988-25.
• Bles W, Graaf B de, Bos JE, Groen E, Krol JR. 1997) A sustained hyper-G load as a tool to simulate space sickness. J. Gravitat. Physiol. 4:P1-P4.
• Bos JE, Bles W. (2002) Theoretical considerations on canal-otolith interaction and an observer model. Biological Cybernetics  86:191-207.
• Bos JE, Bles W, Graaf B de. (2002) Eye movements to yaw, pitch, and roll about vertical and horizontal axes: adaptation and motion sickness. Aviation Space and Environmental Medicine  73:436-444.
• Groen E, Graaf B de, Bles W, Bos JE. (1996) Ocular torsion before and after 1 hour 3Gx centrifugation. Brain Res. Bulletin 40:331-335.