title: Identification of a pathway from the retina to koniocellular layer K1 in the lateral geniculate nucleus of marmoset.
abstract: Three well characterized pathways in primate vision (midget-parvocellular, parasol-magnocellular, bistratified-koniocellular) have been traced from the first synapse in the retina, through the visual thalamus (lateral geniculate nucleus, LGN), to the visual cortex. Here we identify a pathway from the first synapse in the retina to koniocellular layer K1 in marmoset monkeys (Callithrix jacchus). Particle-mediated gene transfer of an expression plasmid for the postsynaptic density 95-green fluorescent protein (PSD95-GFP) was used to label excitatory synapses on retinal ganglion cells and combined with immunofluorescence to identify the presynaptic bipolar cells. We found that axon terminals of one type of diffuse bipolar cell (DB6) provide dominant synaptic input to the dendrites of narrow thorny ganglion cells. Retrograde tracer injections into the LGN and photofilling of retinal ganglion cells showed that narrow thorny cells were preferentially labeled when koniocellular layer K1 was targeted. Layer K1 contains cells with high sensitivity for rapid movement, and layer K1 sends projections to association visual areas as well as to primary visual cortex. We hypothesize that the DB6-narrow thorny-koniocellular pathway contributes to residual visual functions ("blindsight") that survive injury to primary visual cortex in adult or early life.
authors.affiliation: Departments of Ophthalmology and Save Sight Institute, Australian Research Council Centre of Excellence in Vision Science, and School of Medical Sciences, The University of Sydney, Sydney, NSW 2000, Australia, Department of Cell Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki, 444-8585, Japan, Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8787, Japan, and Institute of Physiology, Medical School, University of Pécs, 7624 Pécs, Hungary.
authors.forename: Kumiko A
authors.initials: KA
authors.lastname: Percival
authors.forename: Amane
authors.initials: A
authors.lastname: Koizumi
authors.forename: Rania A
authors.initials: RA
authors.lastname: Masri
authors.forename: Péter
authors.initials: P
authors.lastname: Buzás
authors.forename: Paul R
authors.initials: PR
authors.lastname: Martin
authors.forename: Ulrike
authors.initials: U
authors.lastname: Grünert
mesh_terms: D025042:Amacrine Cells / Q000166:cytology / Q000648:ultrastructure; D000818:Animals; D001369:Axons; D002144:Callithrix / Q000033:anatomy & histology*; D048430:Cell Shape; D003712:Dendrites; D005260:Female; D005829:Geniculate Bodies / Q000166:cytology*; D008854:Microscopy, Electron; D056325:Neuronal Tract-Tracers; D012160:Retina / Q000166:cytology*; D051245:Retinal Bipolar Cells / Q000166:cytology / Q000648:ultrastructure; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000648:ultrastructure; D013569:Synapses; D014793:Visual Cortex / Q000166:cytology*; D014795:Visual Pathways / Q000166:cytology*
chemical_list: D056325:Neuronal Tract-Tracers
keywords: bipolar cells; ganglion cells; koniocellular; parallel pathways; primate retina