Audition and the Central Nervous System of Fishes

Abstract

It is impossible to discuss the organization and evolution of otic pathways in fishes without discussing their relationship to the lateral line system, as both systems have been claimed to possess a single phyletic origin (Ayers 1892, Wilson and Mattocks 1897, van Bergeijk 1966, 1967) and terminate in the same primary medullar nuclei (Mayser 1882, Herrick 1897, Pearson 1936, Larsell 1967). In examining the development of the lateral line and otic systems in Salmo, Wilson and Mattocks (1897) claimed that both systems arose from a single sensory placode and suggested that the inner ear arose phylogenetically by a portion of the peripheral lateral line sinking beneath the skin surface. Mayser (1882) examined the central course of the eighth cranial nerve in cyprinids and claimed that both it and the lateral line nerves terminate in the “acoustic tubercle” of the medulla. Mayser suggested that the lateral line system of fishes should be viewed as an accessory auditory system, based on convergence of the otic and lateral line efferents. The “acoustic tubercle” of fishes thus became known as the acousticolateral area, and the inner ear’s proposed origin from a portion of the lateral line system is known as the acousticolateralis hypothesis.