Eye movement dynamics in the dogfish.

A method is described of obtaining the relationship between electrical stimulation of the abducens nerve and horizontal eye movement in the dogfish. The stump of the VIth nerve was stimulated intracranially in a fish in which the brain had been removed, but in which the circulation remained intact, and the gills were perfused with sea water. Horizontal rotation of the eye was monitored with an opto-electronic movement detector. Eye rotation was linearly related to stimulus frequency in the 0-20 Hz range, and was maximal at frequencies above 40 Hz. Stimulation of the VIth nerve, with a pulse train whose frequency was modulated sinusoidally between 0 and 20 Hz, produced sinusoidal eye movements. The frequency response of the system approximates a first order low pass filter with a characteristic frequency of 0.23 Hz, and an additional phase lag equivalent to a time delay of approximately 50 ms.