Document Detail

Fibre organization of the monkey's optic tract: I. Segregation of functionally distinct optic axons.
MedLine Citation:
PMID:  2351758     Owner:  NLM     Status:  MEDLINE    
The fibre organization of the monkey's optic tract was examined by implanting pellets of horseradish peroxidase into different locations within the tract, or into the superior colliculus and pretectum. Retinae were examined for the distribution, size, and morphological types of retrogradely labelled ganglion cells; optic tracts were examined for the distribution of anterogradely and retrogradely labelled axonal profiles; and lateral geniculate nuclei were examined for the distribution of anterogradely labelled processes within distinct geniculate laminae. Localized implants in the optic tract produced retrograde labelling of ganglion cells across wide regions of the retinal surface. The maximum density of labelled cells was always substantially less than the total ganglion cell density known to be present at those retinal loci. Distinct retinal ganglion cell types were labelled from differing regions within the optic tract: implants into the deep (dorsal) portion of the tract, far removed from the outer, pial, surface, retrogradely labelled predominantly P beta retinal ganglion cells, whereas implants into the superficial (ventral), subpial, part of the tract retrogradely labelled primarily the other retinal ganglion cell types, i.e., the P alpha, P gamma, and P epsilon cells. Within any given class of axon, there is a mapping of the centroperipheral retinal axis across the deep-to-superficial dimension of the tract, but this retinotopy is extremely coarse. Anterograde labelling of axonal terminations within the lateral geniculate nucleus showed a corresponding specificity for distinct geniculate laminae, the deep implants labelling the parvocellular laminae, superficial implants labelling the magnocellular laminae. Implants into the visual centres of the midbrain produced retrograde axonal labelling rostral to the lateral geniculate nucleus only in the superficial part of the optic tract. These results demonstrate that the monkey's optic tract is not a simple topographic mapping of retinal eccentricity. Rather, the primary organizational principle is that of a segregation of functionally distinct optic axon classes. As fibre order in the mammalian optic tract is also a chronological index of axonal arrival during development, the present results provide specific predictions about the temporal order of ganglion call genesis and axonal addition within the visual pathway. They also provide an anatomical basis for the functionally selective visual impairments that may arise following local damage to the optic tract in humans.
B E Reese; A Cowey
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of comparative neurology     Volume:  295     ISSN:  0021-9967     ISO Abbreviation:  J. Comp. Neurol.     Publication Date:  1990 May 
Date Detail:
Created Date:  1990-07-16     Completed Date:  1990-07-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0406041     Medline TA:  J Comp Neurol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  385-400     Citation Subset:  IM    
Department of Human Anatomy, University of Oxford, England.
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MeSH Terms
Axons / ultrastructure*
Geniculate Bodies / cytology*
Horseradish Peroxidase / diagnostic use
Macaca / anatomy & histology*
Macaca fascicularis
Macaca mulatta
Optic Chiasm / cytology*
Retina / cytology*
Retinal Ganglion Cells / cytology*
Visual Pathways / anatomy & histology
Reg. No./Substance:
EC 1.11.1.-/Horseradish Peroxidase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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