CELL DENSITIES IN THE VARIOUS LAYERS OF THE RABBITS STRIATE AREA

The numbers of nerve cells and glial cells as well as the total number of cells per unit volume of 106 μm3, i.e. in a cube with a side length of 100 μm, were determined for the various layers of the striate area of perfusion-fixed, paraffin-embedded brains of adult rabbits. The results obtained in 10 hemispheres as well as average values obtained by combining the measurements on 175 sections from 7 of the hemispheres are described and illustrated by graphs showing cell densities as a function of depth of cerebral cortex. In a typical curve, nerve cell density is below 10 cells per unit volume in layer I, reaches the first peak of more than 80 in layer II/III, a maximum of about 120 in layer IV and has a smaller peak of just below 70 in the upper part of layer VI. Glial cell density decreases from more than 30 cells per unit volume in the upper parts of layer I to less than 20 in layer II/III; it then increases very slowly to about 30 at the border of layer V to VI; in layer VI it begins to rise steeply and reaches its maximum of more than 90 cells per unit volume beyond the border between grey and white matter. To permit the results to be used for the interpretation of electrophysiological findings, an attempt is made in the discussion to correct the average densities, as well as the depth parameter of a typical curve, for tissue shrinkage and to construct a curve for what may, in fact, be encountered in the living brain. © 1979 Springer-Verlag.