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Structure of the piriform cortex of the opossum. I. Description of neuron types with golgi methods
Author(s) -
Haberly Lewis B.
Publication year - 1983
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.902130205
Subject(s) - biology , soma , neocortex , dendritic spine , opossum , piriform cortex , neuron , anatomy , dendrite (mathematics) , neuroscience , apical dendrite , golgi apparatus , axon , pyramidal cell , microbiology and biotechnology , central nervous system , endoplasmic reticulum , geometry , mathematics , hippocampal formation
The piriform cortex was studied in the adult opossum with rapid Golgi and Golgi‐Cox techniques. Most pyramidal cells in the deep part of layer II and layer III resemble those in other parts of the cerebral cortex by virtue of a single apical dendritic trunk, multiple basal dendrites, a large number of small to medium dendritic spines, and a deeply directed axon. Pyramidal cells in the superficial part of layer II are similar with the exception that “secondary” apical dendrites often emerge directly from the cell body rather than from a single primary trunk. With conservative criteria for categorization, nine different types of nonpyramidal cells were distinguished, four of which have not been previously described. Layer I contains a small number of neurons with both smooth and spiny dendrites including distinctive fusiform cells with large somatic appendages. As in other species, the most common type of nonpyramidal neuron in layer II is the semilunar cell which has only apically directed dendrites. These cells have distinctive large spines confined to their distal dendritic segments. The mid to deep portion of layer III contains multipolar neurons with smooth dendrites that resemble the well‐known large stellate cells in neocortex. In addition, layer III contains three non‐pyramidal neuron types with spiny dendrites: (1) fusiform and multipolar cells with complex, branched dendritic appendages and somatic spines, (2) very large multipolar cells (up to 35 μm mean diameter) with large‐diameter dendrites that give rise to abruptly tapering side branches and filiform spines, and (3) multipolar cells with profusely spiny dendrites. In all three layers, small neurons have been found with spherical cell bodies and “axoniform” dendrites that resemble the so called neurogliaform neurons described in a variety of brain areas. A striking feature of the organization of the piriform cortex is that, with the exception of the neurogliaform neurons, the different types of nonpyramidal cells tend to be segregated in individual layers or sublayers. Physiological implications of the results are discussed. Remarks are also made concerning the potential of the piriform cortex as a model cortical system.