The neuronal composition of area 17 of rat visual cortex. I. The pyramidal cells
- 8 April 1985
- journal article
- research article
- Published by Wiley in Journal of Comparative Neurology
- Vol. 234 (2), 218-241
- https://doi.org/10.1002/cne.902340208
Abstract
The pyramidal cells in area 17 of rat visual cortex have been examined by light microscopy using Golgi preparations and semithin plastic sections, and by electron microscopy. Pyramidal cells have cell bodies in layers II–VIa. The pyramidal cells in the lower portion of layer II/III are typical examples of this neuronal type in that they have pyramidal-shaped cell bodies, apical dendrites which ascend to layer I, and a skirt of basal dendrites. The pyramidal cells in upper layer II/III are similar in form but have shorter apical dendrites, while the most superficial pyramidal cells lack apical dendrites and instead have two or more primary dendrites that emanate from the upper surface of their somata. In layer V the pyramidal cells are of two sizes, medium and large, and both have a typical morphology, although the larger neurons have thicker apical dendrites and better-developed axon hillocks than the medium-sized pyramids. The medium-sized pyramidal cells of layer V outnumber the large ones to a ratio of 2.5:1. In layer IV a few typical medium-sized pyramidal cells are present, but the majority are small and can be regarded as star pyramids for they have dendrites radiating in all directions. No clearly identified spiny stellate cells have been encountered in layer IV. The pyramidal cells of layer VIa are also small, and most of them have apical dendrites which only ascend as far as layer IV. In addition to these varieties, both inverted and horizontally inclined pyramidal cells have been encountered. In electron micrographs it is apparent that although all of the pyramidal cells have symmetric axosomatic synapses, the frequency with which these synapses occur varies. The cell bodies of the various forms of pyramidal cells do not show a standard cytology. The medium-sized pyramidal cells of layer II/III usually have rounded nuclei, while the nuclei of the small pyramidal cells of layers IV and VIa are somewhat more irregular, and the large pyramidal cells of layer V have deeply indented nuclear envelopes. The appearance of the perikaryal cytoplasm also varies. The larger pyramidal cells have numerous mitochondria and well-developed Nissl bodies in their perikaryal cytoplasm, but the smaller cells have much-less-pronounced mitochondria and their rough endoplasmic reticulum is only organized into stacks at the bases of dendrites. Pyramidal cells account for about 87% of profiles of neuronal cell bodies with nuclei in layer II/III, 90% in layer IV, 89% in layer V, and 97% in layer VIa.Keywords
This publication has 34 references indexed in Scilit:
- Bipolar neurons in rat visual cortex: A combined Golgi-electron microscope studyJournal of Neurocytology, 1981
- Three-dimensional aspects and synaptic relationships of a Golgi-impregnated spiny stellate cell reconstructed from serial thin sectionsJournal of Neurocytology, 1980
- Aqualitative and quantitative electron microscopic study of the neurons in the primate motor and somatic sensory corticesPhilosophical Transactions of the Royal Society of London. B, Biological Sciences, 1979
- Interlaminar connections and pyramidal neuron organisation in the visual cortex, area 17, of the Macaque monkeyJournal of Comparative Neurology, 1975
- Meynert cells in the primate visual cortexJournal of Neurocytology, 1974
- An electron microscopic study of the neurons of the visual cortexJournal of Neurocytology, 1974
- An electron microscopic study of the neurons of the primate motor and somatic sensory corticesJournal of Neurocytology, 1973
- Organization of neurons in the visual cortex, area 17, of the monkey (Macaca mulatta)Journal of Comparative Neurology, 1973
- Connections of the cerebral cortex. I. The albino rat. B. Structure of the cortical areasJournal of Comparative Neurology, 1946
- Structure of the area striata of the catJournal of Comparative Neurology, 1941