EFFECT OF SPACEFLIGHT ON ABILITY TO SENSE AND CONTROL ROLL TILT - HUMAN NEUROVESTIBULAR STUDIES ON SLS-2

To measure adaptive changes in the ability to sense tilt after spacefl ight, we measured the ability of four astronauts to control roll tilt in the presence of a pseudorandom motion disturbance before and after a 14-day Spacelab mission. The subjects were tested 1) in the dark, 2) with an independent sum-of-sines visual display, and 3) by using a co ntrol condition in which the visual cues confirmed the motion cues (co unterrotating). The two subjects tested on the landing day exhibited s ignificant decrements (P < 0.05) in their ability to control roll tilt in the dark, whereas no significant performance decrements were obser ved in the control condition. Thc absence of changes in the control co ndition suggests that changes in the neuromuscular component of tile t ask and postflight fatigue were not major factors contributing to the observed performance decrement in tile dark. These findings indicate a n adaptive change in the way the nervous system interprets tilt cues. Readaptation of all responses appeared to be rapid, with a return to p reflight values within 1-2 days after landing.