Gravity affects the preferred vertical and horizontal in visual perceptionof orientation

THE aim of this study was to evaluate the influence of gravity on the repre sentation and storage of visual orientation information. On earth, measurem ents of response time and variability for a task of aligning remembered vis ual stimuli showed a distinct-preference for horizontally and vertically or iented stimuli when the body and gravitational axes were aligned. This pref erence was markedly decreased or disappeared when the body axis was tilted with respect to gravity but was maintained for tests performed in micrograv ity. We conclude that subjects acquire and store visual orientation in a mu lti-modal reference frame that combines proprioceptive and gravitational in formation when both are available. NeuroReport 10:1085-1089 (C) 1999 Lippin cott Williams & Wilkins.