[Effect of blood redistribution on illusional sensations of spatial position in weightlessness].

The study was performed onboard a specially equipped aircraft which allowed zero-g and high-g studies. Blood redistribution was produced using a tilt table (-30 degrees) and a LBNP device. Illusionary sensations were measured by a Birtok unit and subjective reports of the test subjects. In the head-down position the feeling of blood rush to the head disappeared as soon as the weightless state was reached. In most cases illusionary sensations were similar to those in the horizontal position. When exposed to LBNP tests, the subjects developed no illusionary sensations during horizontal flight and felt their upper body going upwards and legs going downwards in the weightless state. Thus, illusionary sensations of the spatial position depend at large on blood redistribution in the human body.