Modification of single neural elements in vestibular nystagmus by anesthesia.

This study sought to identify, at a single neuron level, the mechanism by which the quick phase of vestibular nystagmus depends on the level of consciousness. The activity of one group of neurons in the reticular formation known to project to abducens motoneurons was recorded together with the activity of the contralateral abducens and medial rectus nerves before, during and after 80% nitrous oxide anesthesia. The anesthetic resulted in a progressive reduction of the bursting activity of these premotor neurons with accompanying changes in the abducens and medial rectus discharges. It is concluded that the quick phase of nystagmus is easily affected by anesthesia because at least one group of reticular formation neurons which have been shown to be important in the production of rapid eye movements is particularly susceptible to the effects of even week anesthetics.