Stereological methods in the analysis of neuronal parameters in the central nervous system.

Abstract

SUMMARYThe structure of the central nervous system (CNS) is briefly explained. It is compared with the electronic computer and the differences between the two are stated. The methods of measuring this structure and its function are reported.The surface of the cortex as well as the volume of different grey and white matters making up the brain can macroscopically be evaluated on serial slices with the aid of stereological procedures. There is an exponential correlation between volume of the cortex and volume of brain and body in mammals (Fig. 3).The density of neurons and the lengths of their processes can be examined by light microscopy. An improved procedure of counting neurons in the cortex is described. With regard to mammals it is interesting that the densities of neurons in larger brains are lower than in smaller ones. The correlation is negatively exponential. Man and primates have a higher density of cells than the rest of the mammals; their neurons, however, are small. This corresponds to a specialization that can be considered to represent a miniaturization of the neurons (Fig. 4). The topological analysis of dendritic trees is mentioned. The lengths, surfaces and volumes of processes of cells and the amount of synapses can be measured on electron micrographs. The principles and problems of stereology are described by an example of how to measure the myelinated fibres. Some results of the development of these fibres from birth on are reported upon (Fig. 6). In conclusion, some data of the probable dimensions of the human brain are given.