Abstract
The cytoarchitectonic subdivisions and neuronal classes of the visual wulst were studied by cresyl violet, Golgi Colonnier and rapid Golgi technique. The wulst has been categorized into four laminae viz. the most superficial hyperpallium apicale (HA), intermediate interstitial nucleus of the hyperpallium apicale (IHA), hyperpallium intercalatum (HI), and innermost laminae hyperpallium densocellulare (HD). The wulst neurons have been classified into four main cell types: projection neurons having spinous dendrites and axon projecting widely within the same or different regions; local circuit neurons with aspinous dendrites and local axon arborization; stellate neurons being small with thin sparsely spinous dendrites and small sized granule cells with local axon arborization. The projection neurons are further sub classified into pyramidal (moderately spinous and sparsely spinous) and multipolar neurons (highly spinous, moderately spinous and sparsely spinous). Moderately spinous pyramidal neurons are present in the HA whereas sparsely spinous pyramidal neurons are present in the HD. The highly and moderately spinous multipolar neurons are encountered in the HA, HI and HD whereas moderately and sparsely spinous multipolar neurons are found in the IHA and HD respectively. The granule cells are of two types; spinous and aspinous, restricted only in the IHA. Local circuit neurons are present in all laminae except IHA. Stellate neurons are sparsely spinous found in all the four laminae. The dendrites have spines with small stalk and a knob like head. The morphology of dendritic spines (stalk length and head diameter) varies in different neurons and regions. The present findings have been compared with data reported in the wulst of other birds and also with the neuronal morphology of reptilian dorsal cortex and mammalian visual cortex.
Published Version
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