A Quantitative Study of the Purkinje Cells in the Cerebellum and the Inferior Olivary Neurons in the Chicken

A single olivocerebellar fiber branches off several climbing fibers. One Purkinje cell receives input from only one climbing fiber. A single inferior olivary neuron, therefore, synapses with several Purkinje cells, so that there are more Purkinje cells than the inferior olivary neurons. We aimed to elucidate the numerical ratio of the inferior olivary neurons to Purkinje cells in the chicken. The total numbers were 353,834 +/- 5,274 in the Purkinje cells per the cerebellum and 21,553 +/- 904 in the inferior olivary neurons of both sides. The numerical ratio of inferior olivary neurons to Purkinje cells was 1:16. The ratio of those neurons in mammals is about 1:4-17, so that the ratio in the chicken is within the range of mammals.