title: Early divergence of magnocellular and parvocellular functional subsystems in the embryonic primate visual system.
abstract: In both human and Old World primates visual information is conveyed by two parallel pathways: the magnocellular (M) and parvocellular (P) streams that project to separate layers of the lateral geniculate nucleus and are involved primarily in motion and color/form discrimination. The present study provides evidence that retinal ganglion cells in the macaque monkey embryo diverge into M and P subtypes soon after their last mitotic division and that optic axons project directly and selectively to either the M or P moieties of the developing lateral geniculate nucleus. Thus, initial M projections from the eyes overlap only in prospective layers 1 and 2, whereas initial P projections overlap within prospective layers 3-6. We suggest that the divergence of the M and P pathways requires developmental mechanisms different from those underlying competition-driven segregation of initially intermixed eye-specific domains in the primate visual system.
authors.affiliation: Section of Neurobiology, Physiology, and Behavior, Department of Psychology, and the Center for Neuroscience, University of California, Davis, CA 95616-0657, USA.
authors.forename: C
authors.initials: C
authors.lastname: Meissirel
authors.forename: K C
authors.initials: KC
authors.lastname: Wikler
authors.forename: L M
authors.initials: LM
authors.lastname: Chalupa
authors.forename: P
authors.initials: P
authors.lastname: Rakic
mesh_terms: D000818:Animals; D002585:Cesarean Section; D003118:Color Perception; D005314:Embryonic and Fetal Development; D005260:Female; D005556:Form Perception; D005829:Geniculate Bodies / Q000196:embryology* / Q000502:physiology; D005865:Gestational Age; D006801:Humans; D008251:Macaca / Q000196:embryology*; D008959:Models, Neurological; D009039:Motion Perception; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D012160:Retina / Q000196:embryology* / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014795:Visual Pathways / Q000196:embryology* / Q000502:physiology