Reference frames and internal models studied in microgravity

Gravity plays a role in many different levels of human motor behavior. It dictates the laws of motion of our body and limbs, as well as of the objects in the external world with which we wish to interact. The dynamic interaction of our body with the world is molded within gravity's constraints. The role played by gravity in the perception of visual stimuli and the elaboration of human movement is an active research theme in the field of Neurophysiology. Conditions of microgravity, coupled with techniques from the world of virtual reality, provide a unique opportunity to address these questions concerning the function of the human sensorimotor system. This experiment utilizes the Human Research Facility Computer Workstation and its virtual environment generation accessories as a tool to study these processes of visuo-motor coordination during and after long duration (1-3 month) orbital flight. Restrained and free-floating subjects wear a wide field of view, color stereo head mounted display, and view controlled visual scenes. The subjects perform a number of different test paradigms which assess: 1) the reference frame (head fixed, body fixed, or allocentric) used in grasping remembered objects and 2) the dependence of catching movements on the anticipation of downward acceleration.