Sensation and action during active and passive movement.

In order to determine the cause of active or passive sensation and action, we studied the effect of perception on gaze and posture control. Normal adults and a patient with bilateral labyrinthine loss underwent whole body rotation seated in a chair (120 degrees/s) or standing on a platform (60 degrees/s), while tilting their head with their vision normal or covered. Eye movements were recorded by a CCD video camera and body sways by a force platform. In normal subjects, gaze and posture became ataxic when head tilting with their vision covered, but they remained skilled under conditions of normal vision. The patient with bilateral labyrinthine loss did not undergo the effect of head tilting with no vision. It seems likely that sensation and action, whether they are skilled or ataxic, are controlled by the perception of an outer world which is integrated from visual and vestibular inputs and functions as a vector in the head.