Pretectofugal fibers from the nucleus of the optic tract in monkeys.
The nucleus of the optic tract (NOT) is the visuo-motor relay between the retina and preoculomotor structures in the pathway mediating optokinetic nystagmus (OKN). NOT lesions in monkeys produce no OKN toward the lesioned side. Then, efferent fibers from the NOT course through the brainstem and may reach the vestibular nucleus, which is proposed to be the final nucleus to the motor nucleus. In the present study, the tracer was injected through a micropipette in the NOT in four monkeys. Labeled terminals were observed ipsilaterally in the parabigeminal nucleus, superficial layers of the superior colliculus, dorsal and lateral terminal nuclei of the accessory optic system and pretectal nuclei and contralaterally in the NOT and superficial layers of the superior colliculus. Descending fibers from the NOT consisted of two major pathways: (1) fibers descended medially from the injection site through the reticularis pontis oralis to reach the lateral part of the ipsilateral nucleus reticularis tegmenti pontis; (2) fibers projecting into the dorsal cap of inferior olive, by far the greatest number of labeled fibers, descended ventrally along the lateral border of the reticularis pontis oralis and reached the medial lemniscus where they descended further and branched into the dorsolateral pontine nucleus, the lateral part of the nucleus reticularis tegmenti pontis, the peduncular pontine nucleus, the lateral pontine nucleus, the nucleus prepositus hypoglossi, the medial vestibular nucleus and finally the dorsal cap of the inferior olive. Consistent with the physiological data, the direct terminals to the medial vestibular nucleus could serve to drive the storage mechanisms and to produce OKN in the monkey.
Kato
I
I
Department of Otolaryngology, St. Marianna University School of Medicine, Kawasaki, Japan.
Watanabe
S
S
Sato
S
S
Norita
M
M
D000818:Animals; D001933:Brain Stem / Q000166:cytology; D004525:Efferent Pathways; D008239:Lysine / Q000031:analogs & derivatives; D008251:Macaca; D008636:Mesencephalon / Q000166:cytology*; D008845:Microinjections; D013477:Superior Colliculi / Q000166:cytology*; D014726:Vestibular Nuclei / Q000166:cytology*; D014795:Visual Pathways
C013411:biocytin; D008239:Lysine