Role of Vestibular Nystagmus in the Visual Perception of a Moving Target in the Dark

Abstract

Abstract : Six well-trained subjects reported their visual perceptions both during and following rotation while observing a moving target in the dark and in a lighted room. The subjects were rotated at speeds varying from 2 to 15 rpm both to the right and left, while the target described a circular path 2 meters distant and 15 degrees above the level of the subjects' eyes. The subjects were asked to give a qualitative description of their own sensations of rotation and of the apparent movement of the movement of the model plane during and following rotation. When a subject was accelerated to 15 rpm in the dark, there was a rapid displacement of the target in the opposite direction, although, at the same time, as a result of nystagmus the target appeared motionless. This paradox made it necessary for the subjects to distinguish between rate of motion and amount of displacement. As the target went by on successive rotations, it appeared to pass more rapidly until, after approximately 30 seconds, the subject felt himself to be stationary while the target rotated rapidly around him. Similar results occurred at slower speeds or rotation. The post-rotation phenomena were stronger, since the deceleration was more rapid. These phenomena which did not occur in a lighted room can be considered as a summation of the effects of real motion of the target, vestibular nystagmus, and the subjects' sensations of their own motion.