title: Evidence that blue-on cells are part of the third geniculocortical pathway in primates.
abstract: Colour vision in primates is mediated by cone opponent ganglion cells in the retina, whose axons project to the dorsal lateral geniculate nucleus in the visual thalamus. It has long been assumed that cone opponent ganglion cells project to the parvocellular layers of the geniculate. Here, we examine the role of a third subdivision of the geniculocortical pathway: the interlaminar or koniocellular geniculate relay cells. We made extracellular recordings in the dorsal lateral geniculate nucleus of the common marmoset Callithrix jacchus, a New World monkey in which the interlaminar cells are well segregated from the parvocellular layers. We found that one group of colour opponent cells, the blue-on cells, was largely segregated to the interlaminar zone. This segregation was common to dichromatic ('red-green colour-blind') and trichromatic marmosets. The result calls into question the traditional notion that all colour information passes through the parvocellular division of the retino-geniculo-cortical pathway in primates.
authors.affiliation: Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW, Australia.
authors.forename: P R
authors.initials: PR
authors.lastname: Martin
authors.forename: A J
authors.initials: AJ
authors.lastname: White
authors.forename: A K
authors.initials: AK
authors.lastname: Goodchild
authors.forename: H D
authors.initials: HD
authors.lastname: Wilder
authors.forename: A E
authors.initials: AE
authors.lastname: Sefton
mesh_terms: D000818:Animals; D002144:Callithrix / Q000502:physiology*; D003118:Color Perception / Q000502:physiology*; D005260:Female; D005829:Geniculate Bodies / Q000166:cytology* / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology* / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*