TACTILE INFLUENCES ON ASTRONAUT VISUAL-SPATIAL ORIENTATION - HUMAN NEUROVESTIBULAR STUDIES ON SLS-2

Human spatial orientation in spaceflight is initially disturbed by the absence of usable graviceptor information from the otolithic organs. Experiments measuring astronaut visually induced motion (vection) stre ngth on various flight clays during the first 10 days of the Spacelab Lifo Sciences-a mission demonstrated two new phenomena in addition to confirming the initial increased weighting of visual and localized tac tile cues. The reliance on tactile and visual noninertial cues apparen tly declined after a week in space, as the crew became able to utilize their internal reference frame. Subjects also showed that even nondir ectional tactile cues served as a direction anchor and inhibited visua lly induced roll sensation relative to a new loosely tethered test con dition. Individual perceptual styles were again revealed among tile fo ur astronauts tested. The readaptation to 1 G, similarly shows a perio d of reinterpretation of inertial and visual cues to spatial orientati on. The results are discussed in terms of an internal-model representa tion of body orientation, with time-varying weights applied to extrins ic and intrinsic signals.