Perception and Action in Altered Gravity

Human perception and action are dramatically influenced by the gravitationalinertial forces (GIFs) in the surrounding environment. Forces due to acceleration and those due to gravity interact with one another, and have virtually identical physical effects. These forces cause novel mechanical loadings of the entire organism, and provide systematically altered stimulation to the otolith organs and the somesthetic receptors. Over the past several years, studies of human spatial orientation, visual localization, force estimation, and hand-eye coordination under a variety of conditions that involve exposure to altered GIFs have revealed how these various functions are influenced by the force environment. This presentation reviews some of our earlier studies, and presents a general framework for examining the effects of altered GIFs on both perception and action. The critical role of motor-sensory feedback in adaptation to altered GIFs is highlighted from the results of these studies.