May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Projection Patterns and Morphology of Koniocellular Pathway Ganglion Cells in Marmoset Retina
Author Affiliations & Notes
  • P. R. Martin
    National Vision Research Institute of Australia, Carlton, Australia
    Optometry & Vision Sciences, University of Melbourne, Melbourne, Australia
  • B. A. Szmajda
    National Vision Research Institute of Australia, Carlton, Australia
    Optometry & Vision Sciences, University of Melbourne, Melbourne, Australia
  • U. Grunert
    National Vision Research Institute of Australia, Carlton, Australia
    Optometry & Vision Sciences, University of Melbourne, Melbourne, Australia
  • Footnotes
    Commercial Relationships P.R. Martin, None; B.A. Szmajda, None; U. Grunert, None.
  • Footnotes
    Support NHMRC Grant 25362
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 3177. doi:
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      P. R. Martin, B. A. Szmajda, U. Grunert; Projection Patterns and Morphology of Koniocellular Pathway Ganglion Cells in Marmoset Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3177.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose:: To understand the role of parallel afferent pathways in primate color vision, we analyzed retinal projections to the lateral geniculate nucleus.

Methods:: Geniculate-projecting ganglion cells were labeled by photofilling [1] following targeted injections of retrograde tracer centered on parvocellular (PC), magnocellular (MC) and koniocellular (KC) layers in sufentanil-anaesthetized marmosets. The morphological diversity of these retrograde-labeled (geniculate projecting) cells was compared with a random sample of intracellularly injected (undetermined projection) ganglion cells.

Results:: Consistent with previous studies in macaque, the dominant projection to the PC layers was from midget class ganglion cells and the dominant projection to the MC layers was from magnocellular cells. Cells labeled after injections centered on KC layers included several non-midget, non-parasol cell types (wide-field cells). Diversity was estimated quantitatively by unsupervised classification using hierarchical clustering. Four morphological measures (dendritic field diameter, depth and breadth of dendritic stratification in the inner plexiform layer, and the number of dendritic branches) allowed midget, parasol and wide-field cells to be distinguished automatically with over 85% correspondence to subjective categorization. This automatic process yielded 2 main clusters of wide-field cells, of which one (including small bistratified, and sparsely-branching ganglion cells) included the most commonly labeled of geniculate-projecting wide-field cells.

Conclusions:: Because the small bistratified cells, and some sparse cell types, transmit signals originating in short-wavelength sensitive ("blue") cone photoreceptors, our results suggest that a major role of the koniocellular pathway in diurnal primates is to serve the blue-yellow axis of color vision.[1] Dacey et al. (2003) Neuron 37:15-27.

Keywords: ganglion cells • color vision • thalamus/lateral geniculate nucleus 
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