ACCURATE VISUAL FEEDBACK ENHANCES LEARNING OF MANIPULATION IN ALTERED GRAVITY O.White1,3; G.Blohm1,2*; J.Thonnard3; P.Lefèvre1,2 1. Cesame, 2. Lab Neurophysiol, 3. Rehabil & Phys Med Unit, Univ catholique de Louvain, Louvain-La-Neuve, Belgium A hand-held load pursuing a complex trajectory undergoes gravitational and centripetal accelerations that both contribute to the load force. To prevent accidental slip, the grip force has to be adjusted to the load force fluctuations. Here, we investigated the role of visual feedback for manipulation in new gravitational environments. During parabolic flights (1g, 2g, 0g gravity), six subjects (3 naive) were asked to rhythmically bypass two virtual obstacles in front of them with an instrumented hand-held load following a lemniscate trajectory. Two different visual feedback conditions (straight ahead fixation or saccades between the obstacles) were alternated between parabolas. We measured the grip and load forces, 3D kinematics and eye movements and analyzed the influence of gravity, viewing condition and repetition on learning across trials. First, the time lag between grip and load forces was small in all gravitational fields, indicating a good prediction of the new constraints. Also, the correlation between grip and load forces improved across trials as a result of short-term adaptation. Furthermore, this adaptation was better for experienced than for naive subjects. Second, in the saccade condition, eye movements were found to optimize the visual information about obstacles, as revealed by the timing of saccades. Third, as compared to visual fixation, the variability of the trajectory decreased for the saccade condition. We also found a better adjustment of grip to the gravitational load force component when saccades were executed. In conclusion, we provide evidence for an influence of eye movements on object manipulation. Indeed, optimal visual information enhanced learning in new gravitational environments. Thus, internal models of grip force control need adequate visual information to adapt to altered gravity. Support Contributed By: Prodex, SSTC, FNRS, ESA Citation:O. White, G. Blohm, J. Thonnard, P. Lefèvre. ACCURATE VISUAL FEEDBACK ENHANCES LEARNING OF MANIPULATION IN ALTERED GRAVITY Program No. 994.2. 2004 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2004. Online.