COMPLEXITY AND SCALING PROPERTIES OF AMACRINE, GANGLION, HORIZONTAL, AND BIPOLAR CELLS IN THE TURTLE RETINA

In the present study we have evaluated the complexity and scaling prop erties of the morphology of retinal neurons using fractal dimension as a quantitative parameter. We examined a large number of cells from Ps eudemys scripta and Mauremys caspica turtles that had been labeled usi ng Golgi-impregnation techniques, intracellular injection of Lucifer Y ellow followed by photooxidation, intracellular injection of rhodamine conjugated horseradish peroxidase, or intracellular injection of Luci fer Yellow or horseradish peroxidase alone. The fractal dimensions of two-dimensional projections of the cells were calculated using a box c ounting method. Discriminant analysis revealed fractal dimension to be a significant classification parameter among several other parameters typically used for placing turtle retinal neurons in different cell c lasses. The fractal dimension of amacrine cells was significantly corr elated with dendritic field diameters, while the fractal dimensions of ganglion cells did not vary with dendritic held span. There were no s ignificant differences between the same cell types in two different tu rtle species, or between the same types of neurons in the same species after labeling with different techniques. The application of fractal dimension, as a quantitative measure of complexity and scaling propert ies and as a classification criterion of neuronal types, appears to be useful and may have wide applicability to other parts of the central nervous system. (C) 1994 Wiley-Liss, Inc.