Reduced density of geniculocortical terminals in foveal layer 4A in the macaque primary visual cortex: relationship to S-cone density

Virginia Garcia-Marin, Marina Sundiang, Michael J. Hawken

Research output: Contribution to journalArticle


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.

Original languageEnglish (US)
Pages (from-to)2783-2796
Number of pages14
JournalBrain Structure and Function
Issue number5
StatePublished - Sep 28 2015



  • Macaque
  • S-cones
  • Thalamic afferents
  • Vesicular glutamate transporter
  • Visual cortex

ASJC Scopus subject areas

  • Anatomy
  • Neuroscience(all)
  • Histology

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