Ocular rotation and perception of the horizontal under static tilt conditions in patients without labyrinthine function.

In a previous study (1) it was found that in healthy subjects Ocular (Counter) Rotation is mainly due to otolith stimulation and only to a minor extent induced by slanted visual structures. Stimulation of the neck by tilting the trunk laterally upwards did not result in a systematic rotation of the eyes. In the present study it was found that subjects with bilateral loss of vestibular function showed a higher visually induced ocular rotation. Tilting the head (cervical stimulation) or the whole body (somatosensory stimulation) also led to a considerable OCR, demonstrating substitution of other sensory modalities for the loss of vestibular function. Estimates of the subjective horizontal were noisy, demonstrating the lack of an adequate gravitational reference signal.