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The lateral geniculate nucleus of the marsupial phalanger, Trichosurus vulpecula . An experimental study of cytoarchitecture in relation to the intranuclear optic nerve projection fields
Author(s) -
Hayhow W. R.
Publication year - 1967
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901310412
Subject(s) - anatomy , biology , superior colliculus , lateral geniculate nucleus , optic nerve , optic tract , geniculate , cytoarchitecture , diencephalon , nucleus , thalamus , retina , neuroscience , central nervous system
From a cytoarchitectural viewpoint four laminae are apparent in the normal dorsal lateral geniculate nucleus of the marsupial phalanger. The contra‐ and ipsilateral Nauta preterminal degeneration patterns produced by previous unilateral optic nerve section have been precisely delineated and related to these laminae. The terminations of the optic nerve fibers fractionate the nucleus into six laminae of which the crossed and uncrossed optic fibers each mainly supply three; crossed fibers terminate in laminae 2a, 3 and 6, uncrossed fibers terminate in laminae 1, 2b and 4+5. The “crossed” and “uncrossed” laminae alternate. Concealed lamination is a prominent and hitherto unsuspected characteristic of the organisation of the phalanger lateral geniculate nucleus. The most superficial lamina (1) is unusual in so far as it is mainly “uncrossed”. No other reported mammal except the primitive primate Tupaia shows this feature. Although the two intranuclear optic nerve projection fields are largely segregated, the segregation is only complete in laminae 3 and 4+5. Binocular overlap occurs in the remaining laminae, particularly in lamina 2b. The ventral lateral geniculate nucleus and the pretectal nuclear complex are confirmed as primary optic centers supplied by both crossed and uncrossed optic nerve fibers. Within the superior colliculus cells of the zonal, superficial gray and optic layers are in synaptic relationship with crossed fibers while the ipsilateral optic nerve fibers mainly terminate in a circumscribed region of the optic layer. There is no evidence that any component of the lateral thalamic nuclear complex is a terminal center for nerve fibers of retinal origin.