Oculomotor nucleus afferents in the monkey demonstrated with horseradish peroxidase

The afferents to the oculomotor nucleus were examined in the macaque monkey by means of horseradish peroxidase. The demonstration of afferents from the contralateral interstitial nucleus of Cajal, and from the nearby rostral interstitial nucleus of the medial longitudinal fasciculus, predominantly ipsilateral to the injection site, confirms the significant role of these two regions as premotor structures. HRP label in the pretectal area was strictly confined to the olivary nucleus and the corresponding pathway seems to concern the Edinger-Westphal nucleus in particular. A purely crossed internuclear pathway emanating from the abducens nucleus could be established, and evidence for the presence of intranuclear connections within the oculomotor complex itself was found. Ipsilateral afferents from the superior vestibular nucleus and bilateral connections from the medial vestibular nucleus and the y-group were prominent. A projection, showing some rostrocaudal organization within the oculomotor nucleus, arises from the ipsilateral perihypoglossal complex, and other afferents originated from the underlying medullary reticular formation. No evidence was found for the existence of afferents from the paramedian pontine reticular formation, the nucleus Darkschewitsch, the nuclei of the posterior commissure, the lateral tegmentum and the dentate nucleus.