Physiological identification of midbrain neurons related to lens accommodation in cats.

Single units were sought in the medial midbrain, whereas lens accommodation of the eye was monitored by using an infrared high-speed optometer. Nineteen of 135 units isolated were identified as accommodation-related units by two criteria: 1) they discharged in synchrony with spontaneously occurring accommodation, and b) the units were driven by stimulating the interpositus nucleus of the cerebellum. In eight other experiments, units were sought that were antidromically activated by stimulating parasympathetic preganglionic fibers to the ciliary ganglion. Eleven of 46 antidromically activated units were identified as accommodation-related units (accommodation-related oculomotor units). Accommodation-related oculomotor units were found in the medial midbrain within 1 mm of the midline. The majority of them were located lateral and dorsal to the Edinger-Westphal nucleus.