title: Reduced density of geniculocortical terminals in foveal layer 4A in the macaque primary visual cortex: relationship to S-cone density.
abstract: The S-cone system is closely linked to the perception of blue/yellow. The trichromatic system of Old-World monkeys and humans has relatively few S-cones in the fovea. In this study, we investigated the distribution of putative S-cone afferents in macaques primary visual cortex (V1) which form a characteristic honeycomb arrangement in layer 4A. It was hypothesized that if there were a low number of S-cone opponent projecting neurons in central vision then this would be seen as a reduction in afferents in foveal layer 4A. Recent studies have shown that the vesicular glutamate transporter 2 (VGlut2) is a marker for thalamic afferent terminals in cortex. The distribution of VGlut2-immunoreactive (-ir) terminals was studied in the foveal and perifoveal representation of V1. It was found that there was a substantial reduction in the terminal density in the foveal representation: the density was 5-6 times lower in the foveal V1 than in regions representing perifoveal eccentricities of 1°-2° and beyond. These findings may provide the cortical substrate of foveal tritanopia, the reduced blue perceptual ability for small fields in the center of gaze.
authors.affiliation: Center for Neural Science, New York University, 4 Washington Place, New York, NY, 10003, USA.
authors.forename: Virginia
authors.initials: V
authors.lastname: Garcia-Marin
authors.forename: Marina
authors.initials: M
authors.lastname: Sundiang
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hawken
mesh_terms: D000818:Animals; D008251:Macaca; D008252:Macaca fascicularis / Q000378:metabolism*; D009415:Nerve Net / Q000473:pathology; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure*; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism*; D014793:Visual Cortex / Q000378:metabolism* / Q000473:pathology*
chemical_list: D050599:Vesicular Glutamate Transport Protein 2