The course and morphology of efferent nerve fibres in the papilla basilaris of the pigeon (Columba livia).

This paper describes the course and morphology of efferent fibres in an avian cochlea. Horseradish peroxidase stained efferent fibres in the pigeon papilla basilaris were identified by Nomarski optics and camera lucida drawings. There are at least two types of efferent fibres: Large thick fibres take mainly a transversal course and contact short and intermediate hair cells over the free basilar membrane as well as hyaline cells. Large efferent fibres contact both hair cells and hyaline cells. Small thin fibres contact short or intermediate hair cells over the free basilar membrane or tall hair cells over the neural limbus. A physiological consequence of the findings is that efferent activity will concomitantly lead to a contraction of hyaline cells and a hyperpolarization of hair cells.