Subjective velocity estimation during conflicting visual-vestibular stimulation.

Human subjects continuously estimated their position during and after steps of angular acceleration in complete darkness. These estimations were compared with the same vestibular stimulation in the light while subjects gazed at a striped cylinder which completely enclosed them and was mechanically fixed to the turntable. Rotation with such a fixed visual surround created a sensory conflict: the acceleration is sensed by the vestibular end organs, while the visual system senses no displacement. Accordingly, during the conflict stimulation, the estimation of rotational velocity and its duration is markedly reduced. These findings in humans compare well with nystagmus and single neuron recordings in the vestibular nuclei of alert monkeys.