The significance of morphometric procedures in the investigation of age changes in cytoarchitectonic structures of human brain.

The investigations were performed on NISSL-stained cytoarchitectonic images of totally 78 human brains (aged between 18 and 111 years) in the frontal area 11 (inside sulcus olfactorius) with 60 samples and in the visual cortex (area 17) with 45 samples. The morphometric measurements were taken by using a semiautomatic equipment. The largest projection areas of neurons were digitized over a drawing mirror. The arrangement of fields made it possible to get values for the total cortex and its layering. During the calculation the age-dependent embedding shrinkage was paid attention to. Therefore, the values concern the fresh tissue. The neuronal and glial densities, the neuronal sizes and size-distributions were calculated by using stereological and statistical principles. The results outline the following points: A basic description of the cytoarchitectonics is given in their qualitative and quantitative aspects. The individual variation shows high differences, which however, are in accordance with a normal statistical distribution. In area 11 we could find a significant difference of neuronal densities between males and females. The cell-sizes and the aging behavior are not different. In area 17 the amount of female brains was too small for statistics. The aging of both areas showed that the densities of neurons and glial cells do not decrease. A small increase may be possible. The neuronal sizes of area 11 are constant up to 60 years, then a distinct decrease can be observed. During aging the size decrease of neurons is very small in area 17. The layer III usually shows a distinct decrease of neuronal size during aging while layer V has a nearly constant size. The results were discussed and compared with other publications. The differences between our results and earlier publications seem to be mainly due to methodical problems. The older papers do and could probably not observe the stereological procedures of measuring and the age differences of the embedding procedures. The main result is that every gray structure of the brain has its own history.