Adaptation

Changed forces of gravity lead to a decrease of sensorimotor coordination. Until now it has not been differentiated between primary influences of weightlessness and secondary influences due to psycho-physiological factors (e.g. stress).

To get a coherent overall picture on the effects of weightlessness on sensorimotor adaptation and performance, it is necessary to examine the complex interaction of stress and motor control, as motor control is conditioned by physiological (endocrine) reactions to environmental conditions and their psychological valuation. Many authors (Fowler, Manzey) speak of a multi-stressor model but do not specify this. Thus further studies are necessary to determine those parameters that could impair human motor control in weightlessness.

During three phases of parabolic flights (1G - 1,8G - 0G) subjects are expected to adapt to a sensorimotor discordance. We plan to evaluate weather the learning process is directly affected by changes of gravitational forces (0G – 1,8G) as reported previously or if the disturbance is due to secondary, psycho-physiological parameters.

A sensorimotor tracking task is carried out by three different groups of subjects. The subjects’ task will be to follow a free-floating target on a laptop-TFT with a joystick driven cursor. During the learning phase physiological, psychological and endocrinological data will be collected.

During the parabolic flight each subject will be placed in one of the back seats of A300 Zero-G a laptop-TFT being mounted approx. 30 cm in front of the subjects. All subjects will be asked to hold a joystick with their preferred hand, which will be fixed to the left or right armrest. In order to prevent compensatory movements due to weightlessness, subjects will be fixed very firmly to the seat with a safety belt.

A permanent venous catheter for blood collection during flight will be inserted in the arm of the non-dominant hand. A blood collection under rest conditions will be taken prior to take off. Blood collection for determining hormones and catecholamines will be done after parabolas 1, 10, 20 and after the last parabola. Blood samples will have to be centrifuged during parabolic flights.

The learning task will be practiced during the pull-up phase of the plane (group C), during weightlessness (group B), and during the 1G-phases between the parabolas (group A). The learning task will be performed 25 times (trials). Therefore there will be a corridor of five parabolas for any technical or experimental problems.

The collection of psychological parameters will be carried out by Pocket PC prior to take off as well as during the 4 to 8-minute breaks after parabolas 5, 10, 15, 20 and 25, and after the last parabola.

Measurement of EEG, heart rate and respiratory events will be performed continuously during the flight for all three groups. EEG-cap, chest-straps and oxygen sensors will be attached to the subjects an hour prior to take off.

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