EGOCENTRIC REFERENCES AND HUMAN SPATIAL ORIENTATION IN MICROGRAVITY

This article describes the results of the ''ellipses'' experiment cond ucted during the second French-Soviet spaceflight (project Aragatz). T he realization of oriented motor tasks, on the basis of internal body representation and without visual feedback, was chosen as a paradigm f or studying the determinants of spatial orientation under weightlessne ss. The process of drawing ellipses in the air, using arm movements wi th axes parallel or perpendicular to the longitudinal body axis, was s tudied under normal gravity and in weightlessness, and recorded using a video computer motion-analyzing system (Kinesigraph). On Earth, the experiments were performed in standing and lying positions, and in fli ght, in the erect position with the feet fixed to the floor. In genera l, performance of the task in microgravity was not disturbed. Under co nditions of spaceflight, the longitudinal ellipse was inclined forward in accordance with the inclination of the whole body relative to the fixed feet. On Earth, the angle between the long axes of longitudinal and transverse ellipses deviated from 90-degrees by 20-30-degrees. The same deviation persisted under microgravity conditions. The distincti ve features of ellipses traced by individual subjects were also preser ved. It is concluded that an egocentric reference system ensures norma l performance of sensorimotor tasks in the absence of a gravitational reference.