Alexander's law: Its behavior and origin in the human vestibulo-ocular reflex
Article first published online: 16 OCT 2004
Copyright © 1984 American Neurological Association
Annals of Neurology
Volume 16, Issue 6, pages 714–722, December 1984
How to Cite
Robinson, D. A., Zee, D. S., Hain, T. C., Holmes, A. and Rosenberg, L. F. (1984), Alexander's law: Its behavior and origin in the human vestibulo-ocular reflex. Ann Neurol., 16: 714–722. doi: 10.1002/ana.410160614
- Issue published online: 16 OCT 2004
- Article first published online: 16 OCT 2004
- Manuscript Accepted: 21 APR 1984
- Manuscript Revised: 19 APR 1984
- Manuscript Received: 7 FEB 1984
Alexander's law refers to the phenomenon in which the spontaneous nystagmus of a patient with a vestibular lesion is more intense when the patient looks in the quick-phase than in the slow-phase direction. Alexander's law was investigated in normal subjects as well as patients with vestibular lesions. During sinusoidal rotations of normal subjects, there was no trace of this phenomenon when subjects looked 25 degrees left and right in the dark. The phenomenon of Alexander's law is therefore created centrally and is not due to any mechanical properties of the orbit.
During rotation at constant velocity in the dark, normal subjects did weakly demonstrate Alexander's law because of a mild gaze-evoked nystagmus present in normal subjects in the dark. Gaze-evoked nystagmus from a cerebellar lesion involved a pronounced demonstration of Alexander's law during rotatory nystagmus. In patients with a vestibular lesion and a mild spontaneous nystagmus in the dark that obeyed Alexander's law, the nystagmus reversed upon far gaze in the slow-phase direction. We propose that in patients with a vestibular lesion, the phenomenon of Alexander's law is created by the sum of vestibular nystagmus and an abnormally large gaze-evoked nystagmus that is consequent to the vestibular lesion. This conclusion has a number of neurological implications concerning the ways in which the nervous system attempts to compensate for vestibular lesions.