The pretectal complex of the monkey: a reinvestigation of the morphology and retinal terminations.

The cytoarchitecture of the pretectal complex of the squirrel monkey was examined in Nissl- and myelin-stained sections in the coronal, horizontal, and sagittal plane. Five different pretectal subdivisions can be identified on the basis of their nuclear morphology. The general location and cytoarchitecture of these pretectal nuclei are similar to those described for non-primate mammals. Thus, the nomenclature used to designate the pretectal nuclei in other species can now be applied to the squirrel monkey. According to this standard terminology, the pretectal complex of the squirrel monkey consists of the nucleus of the optic tract; the pretectal olivary nucleus; and the medial, anterior, and posterior pretectal nuclei. The pattern of retinal innervation to the pretectum was also determined by placing intraocular injections of 3H-proline into one eye and processing the tissue according to standard autoradiographic techniques. The pattern of transported label is more dense over the contralateral nuclei than over the ipsilateral nuclei. In particular, dense transported label is observed bilaterally over the pretectal olivary nucleus and the nucleus of the optic tract with sparse label over the posterior and medial pretectal nuclei.