Circularvection about earth-horizontal axes in bilateral labyrinthine-defective subjects

A stationary subject surrounded by a visual display rotating about an earth-horizontal axis typically experiences a sensation of continuous self-rotation (vection) coupled with a paradoxical sensation of a limited degree of body tilt, both opposite to the direction of the stimulus. The sensation of limited body tilt has been attributed to conflict between visually-induced vection, and otolithic and somatosensory graviceptive information which indicates that the body has not moved. We investigated circularvection and illusory body tilt about the horizontal axis in the pitch and roll planes in bilateral labyrinthine-defective (L-D) subjects. Results demonstrated that the bilateral group experienced complete unambiguous self-rotation through an upside-down orientation. The relative contributions of the otolithic and somatosensory graviceptors to visuall-induced tilt is discussed.