A laminar analysis of the number of round‐asymmetrical and flat‐symmetrical synapses on spines, dendritic trunks, and cell bodies in area 17 of the cat
- 8 January 1985
- journal article
- research article
- Published by Wiley in Journal of Comparative Neurology
- Vol. 231 (2), 180-189
- https://doi.org/10.1002/cne.902310206
Abstract
The number of synapses per unit volume of tissue (Nv) has been estimated in individual laminae of the binocular and monocular regions of area 17 in six adult cats by using a method of size‐frequency distribution. Separate estimates were obtained for RA synapses (containing round vesicles associated with asymmetric membrane differentiations) and for FS synapses (containing flat vesicles associated with symmetric membrane differentiations). For the total cortical thickness, the Nv of all synapses is not statistically different between binocular (286 million per mml3) and monocular (281 million) regions, nor is it different between the two regions for any of the laminae. Eighty‐four percent of synapses are of the RA type. of those, 79% are found on dendritic spines, 21% on dendritic trunks, 0.1% on somata. FS synapses represent 16% of the total, with 31% of them on spines, 62% on dendritic trunks, and 7% on somata. The ratio of RA to FS synapses is kept relatively constant throughout the layers. A two‐way analysis of variance shows no difference in the Nv of either RA or FS synapses in the two regions nor in the Nv of RA synapses between cats. It does, however, clearly demonstrate (p < 0.001) interindividual differences for FS synapses. These variations between individual cats may be due to differences in age, breed, or environmental factors. In contrast to the relative uniformity of the Nv of synapses between regions, the number of each type under 1 mm2 of cortical surface is 33% higher in the binocular region. This is due mainly to the greater thickness of the binocular region.Keywords
This publication has 53 references indexed in Scilit:
- Efferent systems of primary visual cortex: A review of structure and functionBrain Research Reviews, 1983
- The postnatal development of synapses in the different laminae of the visual cortex in the normal kitten and in kittens with eyelid sutureDevelopmental Brain Research, 1983
- The number of neurons in the different laminae of the binocular and monocular regions of area 17 in the catJournal of Comparative Neurology, 1983
- Frequency specific effects of stroboscopic rearing in the visual cortex of the rabbitDevelopmental Brain Research, 1983
- Cytology and time of origin of interstitial neurons in the white matter in infant and adult human and monkey telencephalonJournal of Neurocytology, 1980
- Anatomical organization of the primary visual cortex (area 17) of the cat. A comparison with area 17 of the macaque monkeyJournal of Comparative Neurology, 1979
- Aspinous and sparsely-spinous stellate neurons in the visual cortex of rats contain glutamic acid decarboxylaseJournal of Neurocytology, 1978
- A comparison of visual pathways in Boston and Midwestern Siamese catsJournal of Comparative Neurology, 1977
- Laminar patterns of geniculocortical projection in the catBrain Research, 1976
- Estimation of the number of synapses in a volume of nervous tissue from counts in thin sections by electron microscopyJournal of Neurocytology, 1974