title: Axon topography of layer 6 spiny cells to orientation map in the primary visual cortex of the cat (area 18).
abstract: To uncover the functional topography of layer 6 neurons, optical imaging was combined with three-dimensional neuronal reconstruction. Apical dendrite morphology of 23 neurons revealed three distinct types. Type Aa possessed a short apical dendrite with many oblique branches, Type Ab was characterized by a short and less branched apical dendrite, whereas Type B had a long apical dendrite with tufts in layer 2. Each type had a similar number of boutons, yet their spatial distribution differed from each other in both radial and horizontal extent. Boutons of Type Aa and Ab were almost restricted to the column of the parent soma with a laminar preference to layer 4 and 5/6, respectively. Only Type B contributed to long horizontal connections (up to 1.5 mm) mostly in deep layers. For all types, bouton distribution on orientation map showed an almost equal occurrence at iso- (52.6 ± 18.8 %) and non-iso-orientation (oblique, 27.7 ± 14.9 % and cross-orientation 19.7 ± 10.9 %) sites. Spatial convergence of axons of nearby layer 6 spiny neurons depended on soma separation of the parent cells, but only weakly on orientation preference, contrary to orientation dependence of converging axons of layer 4 spiny cells. The results show that layer 6 connections have only a weak dependence on orientation preference compared with those of layers 2/3 (Buzás et al., J Comp Neurol 499:861-881, 2006) and 4 (Karube and Kisvárday, Cereb Cortex 21:1443-1458, 2011).
authors.affiliation: Laboratory for Cortical Systems Neuroscience, Department of Anatomy, Histology and Embryology, University of Debrecen, Debrecen, 4032, Hungary.|Graduate School of Brain Science, Doshisha University, Tataramiyakodani 1-3, Kyotanabe, Kyoto, 610-0394, Japan.
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Karube
authors.affiliation: Laboratory for Cortical Systems Neuroscience, Department of Anatomy, Histology and Embryology, University of Debrecen, Debrecen, 4032, Hungary.|Department of Neurosciences Fondamentales, Centre Médical Universitaire, Rue Michel-Servet 1, 4, 1211, Geneva, Switzerland.
authors.forename: Katalin
authors.initials: K
authors.lastname: Sári
authors.affiliation: Laboratory for Cortical Systems Neuroscience, Department of Anatomy, Histology and Embryology, University of Debrecen, Debrecen, 4032, Hungary. kisvarday@anat.med.unideb.hu.
authors.forename: Zoltán F
authors.identifier: 0000-0002-7535-8141
authors.initials: ZF
authors.lastname: Kisvárday
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000502:physiology*; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D001931:Brain Mapping; D002415:Cats; D003712:Dendrites / Q000502:physiology* / Q000648:ultrastructure; D003911:Dextrans / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D009474:Neurons / Q000145:classification / Q000166:cytology*; D009949:Orientation / Q000502:physiology*; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism; D014793:Visual Cortex / Q000166:cytology*
chemical_list: D003911:Dextrans; D050599:Vesicular Glutamate Transport Protein 2; C076397:biotinylated dextran amine; D001710:Biotin
keywords: 3D reconstruction; Apical dendrite; Bouton overlap; Optical imaging; Pyramidal cell