Ocular accommodation in the cat after electrical stimulation of mesencephalic reticular formation

We measured ocular accommodation in the cat with a continuously recording infrared optometer. The brain stem reticular formation in an anesthetized cat was stimulated electrically with microelectrodes to evoke accommodation. Sites in the mesencephalic reticular formation caudal and ventral to the III nerve nucleus near the midline gave large positive accommodation responses. The velocity and amplitude of postive accommodation was graded, depending on the applied current and frequency of stimulation. Relaxation of accommodation proceeded at a fairly constant rate upon cessation of electrical stimulation. These findings provide new information on the amplitude and dynamic aspects of ocular accommodation in the cat. Also, the location of the stimulating electrodes suggest that in addition to the Edinger-Westphal nucleus, areas in the mesencephalic reticular formation between the cerebellum and the oculomotor nucleus are involved in ocular accommodation in the cat.