title: Dendritic structure varies as a function of eccentricity in V1: a quantitative study of NADPH diaphorase neurons in the diurnal South American rodent agouti, Dasyprocta prymnolopha.
abstract: The cerebral cortex is often described as a composite of repeated units or columns, integrating the same basic circuit. The 'ice-cube' model of cortical organization, and 'canonical' circuit, born from insights into functional architecture, still require systematic comparative data. Here we probed the anatomy of an individual neuronal type within V1 to determine whether or not its dendritic trees are consistent with the 'ice-cube' model and theories of canonical circuits. In a previous report we studied the morphometric variability of NADPH-diaphorase (NADPH-d) neurons in the rat auditory, visual and somatosensory primary cortical areas. Our results suggested that the nitrergic cortical circuitry of primary sensory areas are differentially specialized, probably reflecting peculiarities of both habit and behavior of the species. In the present report we specifically quantified the dendritic trees of NADPH-d type I neurons as a function of eccentricity within V1. Individual neurons were reconstructed in 3D, and the size, branching and space-filling of their dendritic trees were correlated with their location within the visuotopic map. We found that NADPH-d neurons became progressively smaller and less branched with progression from the central visual representation to the intermediate and peripheral visual representation. This finding suggests that aspects of cortical circuitry may vary across the cortical mantle to a greater extent that envisaged as natural variation among columns in the 'ice-cube' model. The systematic variation in neuronal structure as a function of eccentricity warrants further investigation to probe the general applicability of columnar models of cortical organization and canonical circuits.
authors.affiliation: Laboratory of Investigations in Neurodegeneration and Infection, Federal University of Pará, Hospital Universitário João de Barros Barreto, Rua dos Mundurucus 4487, 66073-000 Belém/PA, Brazil.
authors.forename: E G
authors.initials: EG
authors.lastname: da Rocha
authors.forename: M A M
authors.initials: MA
authors.lastname: Freire
authors.forename: C P
authors.initials: CP
authors.lastname: Bahia
authors.forename: A
authors.initials: A
authors.lastname: Pereira
authors.forename: M C K
authors.initials: MC
authors.lastname: Sosthenes
authors.forename: L C L
authors.initials: LC
authors.lastname: Silveira
authors.forename: G N
authors.initials: GN
authors.lastname: Elston
authors.forename: C W
authors.initials: CW
authors.lastname: Picanço-Diniz
mesh_terms: D000818:Animals; D001931:Brain Mapping; D016000:Cluster Analysis; D003712:Dendrites / Q000201:enzymology*; D021621:Imaging, Three-Dimensional; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D017966:Pyramidal Cells / Q000166:cytology / Q000201:enzymology; D012377:Rodentia; D014793:Visual Cortex / Q000166:cytology* / Q000201:enzymology; D014795:Visual Pathways / Q000166:cytology* / Q000502:physiology
chemical_list: D009252:NADPH Dehydrogenase