NOTE: Received NCE to 4/30/2008 per K. Major/NSBRI (3/08)

Basic understanding of the roles played by vestibular and other sensors in adaptation to unusual environments, and the associated disorientation and motion sickness, will contribute to astronaut comfort and safety in flight and after landing.

Fundamental studies of the process of sensory-motor adaptation and practical means of controlling motions sickness and sway during rotation are combined in our Specific Aims. In the final year of this project we focused on the theme: Acquisition, Generalization and Retention of Adaptation. We have been able to demonstrate that, with sufficient training, most subjects can tolerate head movements while rotating at speeds up to 30 rpm. The adaptation process is achievable by incremental adjustment of either centrifuge speed, head turn angle or head turn speed. Furthermore, we demonstrate the effectiveness of sleep in consolidating the adaptation.

In addition to the adaptation studies we have explored the effects of exercise on the centrifuge. Finally, we introduced a potentially valuable clinical method for increasing peripheral circulation in the feet during artificial gravity. We intend to continue investigation of this clinical application following termination of the current project. We also intend to explore the effect of gravity gradients in AG on the cardiovascular system through multi-segment dynamic models and experiments.

Understanding motor adaptation to Coriolis forces in an artificial gravity environment is relevant for understanding clinical deficits of whole body movement on earth, because normal body movements generate large inter-segmental Coriolis forces.

Our preliminary results showing an increase in ankle level arterial pressure give promise for the utilization of AG or other related techniques to increase peripheral circulation to the feet, and to help relieve the symptoms felt by diabetics and other patients.

Additionally, a controlled test of three adaptation sessions was conducted with a variation of the sleep period. We demonstrated the effectiveness of sleep in consolidating the previously acquired adaptation to head movements while rotating.

Finally, a test was conducted to assess the increase in the ratio of blood pressure at the ankle to that at heart level during artificial gravity. The results support a clinical spin-off of artificial gravity for the improvement of peripheral circulation.

Understanding motor adaptation to Coriolis forces in an artificial gravity environment is relevant for understanding clinical deficits of complex whole body movement on earth.

Aim 2: 24 subjects have been successfully tested, data analysis almost finished, paper in preparation

Aim 3: Preliminary testing of the SVV-device (subjective visual vertical) took place in November, and a first series of experiments in December 2005. At present we have run 10 subjects and have partially analyzed their data.

Aim 4: The Year 1 sub-aim, which was to compare effects of rotation on quiet stance or voluntary postural oscillations during 10 rpm rotation in the center of a rotating room, was completed. Rotation initially increased sway during both tasks. Over 20 quiet stance trials, sway magnitude did not return to baseline, but in voluntary rocking trials the trajectory of body sway returned to baseline Catch trials showed that adaptation to rocking transferred to quiet stance but there was no transfer in the reverse direction. We have also conducted the experiment for our Year 2-3 sub-aim, which was to expose naïve subjects simultaneously to the vestibular and motor perturbations of posture during rotation or expose them sequentially to vestibular then motor perturbations. The data are being analyzed, and it appears motor adaptation occurs at the same rate in both conditions.

Aim 5: The efficacy of 10, 20 and 30 mg baclofen on reduction of vestibular time constant and the coupling gain to velocity storage was tested. 6 subjects were tested and the results were published. Ongoing experiments test for the effect of 20 mg baclofen on resistance to motion sickness. Seven supine subjects performed head roll movements while spinning at 138º/s were tested with and without baclofen treatment. Preliminary data indicates that subjects made considerable more head movements with baclofen.

Velocity of the centrifuge (Wc)

Velocity of the head turn (Wh)

Amount of the head turn (Th)

Direction of the head turn (Dh)

Position of head relative to axis of rotation (Rh)

Axis of the head turns (yaw, pitch, or roll).

Within a session the level of motion sickness experienced by the subject increases with the number of head turns (n) that are made in the rotating environment while the VOR time-constant, the VOR amount, tumbling intensity, and other sensations decrease. With an increasing number of sessions all symptoms and all measures decrease.

Experiments conducted in 2004:

A) Even though the symptoms of pitch head turns are substantially larger, subjects adapt to pitch head turns as well as to yaw head turns. Performing additional yaw head turns within a protocol that adapts subjects to pitch head turns does not interfere with the pitch adaptation. (46 subjects, September 2003 to May 2004)

B) Incrementing centrifuge velocity (1.5 rpm to 23 rpm) over 5 days leads to adaptation with far less symptoms and therefore the subjects are less likely to dropout due to excessive motion sickness. (15 subjects, June 2004 to September 2004)

C) Cross-coupled stimulation is largely affected by the amount by which the head is turned. A head turn about an angle of 30deg is less provocative and less experienced as less intense as a head turn about an angle of 60deg or 90deg. (21 subjects, April 2004 to September 2004)

D) The effects induced by our standard protocol (MIT & JSC) were tested with six subjects between August 2004 to October 2004.

E) We ran an explorative test series with six subjects for the 6-month study in November and December 2004 re-testing is planed for May 2005 and June 2005.

F) Between September 2004 and December 2004 six subjects were adapted to left yaw head turns (15x to LED and 15xto NU) and tested for right head turns. A preliminary analysis indicates a limited transfer of adaptation from left to right. Several subjects indicated that following the 30 adaptive left head turns, the first 1-2 right head turns were significantly more provocative. At the moment we hypothesize that the initial response to a right head turn -- after being adapted to left head turns -- is high, but decays more rapidly than without the adaptation.

G) Between September 2004 and December 2004 six subjects were adapted to right yaw head turns off-center. A first data analysis indicates that the off-center adaptation leads to slightly different responses than an on-center adaptation: The transfer of adaptation might be "disturbed" because the GIF and the gravity gradient are different in those two positions.

H) Between September 2004 and December 2004 six subjects were adapted to radial movements. No effect on yaw head turns in the right quadrant was found.

I) The construction work needed that allows us to spin at 30rpm was finished in December 2004. Safety checks and testing 30rpm protocols are planed for February 2005, and we expect experiments spinning at 30rpm starting in March 2005.

J) The direction of the HT is a significant and persistent effect in all our protocols involving yaw HT: A HT to NUP leads to larger responses then a HT to RED.

Specific Aim 2: AG and Cognition: Effects of Cross-Coupled Stimulation (CCS) on Performance and Influence of Cognition on Adaptation to AG

Planning and preparation of experiments has finished, start of experiments in February March time frame of 2005.

Specific Aim 3: Does Cross-Coupled Stimulation (CCS) Interfere with Spatial Orientation?

We started first tests of the SVV-device in November and a first series of experiments in December. By now we have run 10 subjects testing for the best type of protocol to be used and their data has been preliminary analyzed.

Specific Aim 4: Adaptation of whole-body movements: experiments in a slow rotation room

Specific Aim 5: Reduction of the Vestibular Time Constant as a Countermeasure against Motion Sickness.

In six subjects the VOR was tested after they have been treated with placebo and 10, 20, and 30mg baclofen. Each subject has been tested seven times in four hours, in total each subject was tested 28 times. To avoid adaptation and effects from the previous test, the test session were about 1 week apart. The test consisted of 2-perrotatory and 2-postrotatory VOR measurements. The analysis for VOR time constants is almost done for all tested subjects and we are still analyzing the data of the VOR gain and the velocity storage coupling gain.