Our nervous system, like the rest of our body, was developed to operate in the presence of gravity, here on the surface of the Earth. As two-legged creatures we humans are particularly dependent on it to determine the direction of the vertical so that we don't fall down - whether walking on a sidewalk or running on the beach. In addition to vision we rely on the vestibular system, the fluid-filled balance organs in the inner ear, to keep us from falling - as well as to stabilize our eyes so that the image of the world doesn't constantly shift as we move around.

All of this balance system usually works well. In fact we are normally conscious of it only when seasick - or in the case of inner ear diseases. In space, however, the whole picture changes. The vertical no longer means anything to the free-floating astronaut - and yet the nervous system is constantly bombarded by signals from the vestibular system. The way the nervous system learns to reorganize itself in space, and again after return to Earth, is one of the many fascinating puzzles we are studying on Neurolab. Both animals and the human crew will serve as subjects of important tests of balance and the effects of gravity. Students and teachers from many universities around the world are involved in this exciting scientific adventure. The results are likely to be of help to people on Earth suffering from gravity-related problems, as well as to pave the way for astronauts of the future to stay in space for longer periods - and maybe even explore Mars.

Larry Young
Apollo Program Professor of Astronautics
Massachusetts Institute of Technology, and
Director, National Space Biomedical Research Institute