COMPLEXITY OF BRANCHING IN DENDRITIC TREES - DEPENDENCE ON NUMBER OF TREES PER CELL AND EFFECTS OF BRANCH LOSS DURING SECTIONING

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 124  (DEC) , 701-715
Abstract
The correlation between the complexity of dendritic trees and the number of primary dendrites per neuron (trees per cell) was studied. To estimate the average number of branches of centrifugal orders 1-5 per tree, specially designed statistical methods were used to compensate for loss of tree parts during sectioning. Neurons from 4 populations, stained by the Golgi-Cox method, were examined: stellate cells from layer IV, area 17 of visual cortex, in normal and dark-reared cats; and pyramidal cells from layer V, somatosensory cortex, in 2 strains of rats. In all 4 goups of neurons the average number of branches of higher order (3,4,5) per tree tended to be smaller in neurons bearing more trees. Thus all trees from a population of neurons should not be assumed to be equivalent. The decrease in high-order branches per tree tended to offset the increase in number of trees per cell. In 3 of the 4 groups these opposed tendencies maintained the average number of high-order branches per neuron nearly independent of the number of trees per cell. Natural selection may have favored near-constancy in the number of high-order branches to reduce dispersion among neurons of 1 type in functional input-output relations.