Neurons and connections of the flocculus in dolphins

Abstract

1. The floccular cortex of the dolphin shows a well-defined stratification. As in other animals it consists of three layers: molecular, ganglionic and granular. 2. Its neuronal composition corresponds to that of the cerebellar cortex of other mammals, except that the Purkinye cells and Golgi cells are characterized by their large size and variety of shapes. 3. Interneuronal connections of the floccular cortex consist mainly of loop synapses and spines. Synapses are most numerous at points of ramification of the main dendritic trunks of Purkinye cells and on dendrites of large stellate Golgi cells. They are few in number on other cortical neurons and are completely absent on the bodies of granule cells. The highest density of spines is observed on dendrites of Purkinye cells. 4. The presence of several varieties of Purkinye cell and the giant size of the Golgi cells, together with the high density of terminal synaptic endings and spines, indicate presumably a high specialization of these neurons and correspond to the level of development of the organ and complexity of its functions in the aquatic mode of life of this animal.