It is difficult to delineate the extent of the cerebellum in fishes because the easily recognized corpus cerebelli lies adjacent to other regions which are essentially cerebellar-like in neural organization. These regions, the auricles and lateral-line areas, relate to the octavolateral sensory system and were considered by Larsell (1967) to form the octavolateral lobe. Nicholson et al. (1969), following Johnston (1902), considered this part of the brain to be the phylogenetic base for the vertebrate cerebellum. The octavolateral region certainly arises from the same rhombencephalic zone as the cerebellar anlage (Rüdeberg 1961), but it is important to recognize that cerebellar-like neural circuits are found in other regions of the vertebrate brain and even in invertebrate nervous systems, and that similarities of internal organization do not necessarily imply homology or a common function (Roberts 1981 b).
KeywordsPurkinje Cell Granule Cell Molecular Layer Parallel Fibre Inferior Olive
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