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The neuronal composition of area 17 of rat visual cortex. III. Numerical considerations
Author(s) -
Peters Alan,
Kara Daniel A.,
Harriman Katherine M.
Publication year - 1985
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.902380303
Subject(s) - neuroscience , biology , neuron , visual cortex , population , stereology , cortex (anatomy) , electron microscope , anatomy , biophysics , physics , endocrinology , medicine , optics , environmental health
The neuronal population of area 17 of rat visual cortex has been examined by using tissue from brains fixed by perfusion. The tissue was osmicated and embedded in plastic so that the same neurons could be examined by both light and electron microscopy. In these preparations area 17 was 1.49 mm thick and by stereological procedures it was calculated that there are about 120,000 neurons beneath 1 mm 2 of cortical surface. If one assumes area 17 in each hemisphere of the rat to occupy between 7.1 and 9.4 mm 2 of cortical surface, then in each hemisphere the area contains between 850,000 and 1,128,000 neurons. Of these neurons 85% are pyramidal cells and 15% are nonpyramidal cells. About one‐third of the nonpyramidal cells occur in layers I and VIb, both of which contain only this kind of neuron. The remaining two‐thirds of the nonpyramidal cells are in layers II‐VIa. Within these layers it has been possible to differentiate bipolar cells from other types of nonpyramidal cells and in each of these two nonpyramidal cell groups to recognize both small and large neurons. The greatest concentration of nonpyramidal cells occurs in layer II/III. To confirm the validity of the stereologically derived data direct counts were made of the medium and large pyramidal cells in layer V.