Regression changes in inferior olivary nucleus compared to changes of Purkinje cells during development in humans.

Human fetal brains were investigated in order to establish the regressional process in two directly dependent structures: in the inferior olivary nucleus and in cerebellar Purkinje cells. Inferior olivary nucleus is the main origin of the climbing fibres, that form one of two direct input systems into the cerebellum. For the purpose 25 fetal human brains at various stages of development (12.5, 15, 16.5 19.5 24, and 31 postovulatory week), together with one brain of newborn (in further text: 41. postovulatory week) were used. Numerical density of nuclei in both regions was determined by stereological technique. In both structures appeared a reduction in the number of nuclei, showing specific dynamics during the intrauterine maturation. The data obtained were analyzed by graphical and numerical method, that allowed the formation of the adequate mathematical models for both structures, that precisely described their regression changes. The data presented indicate that the reduction is very pronounced until the 18-19 postovulatory week, and after that time it is remarkable slowed down. That period is therefore the probable breakpoint of the appearance of synaptic contacts between climbing fibres and Purkinje cell dendrites.