Hormonally-regulated neuron death in the avian brain

Abstract

Birdsong is a sexually dimorphic behavior and neuronal populations contributing to song usually are larger in males than in females. Gonadal steroids establish these sex differences in part by promoting neuron survival during an early sensitive period, thereby preserving neural circuits for song behavior. Also, in at least one species gonadal hormones are implicated in the seasonal death and replacement of song-related neurons that accompanies the yearly restructuring of song. In this review the role of neuron death in establishing and reorganizing the song system is discussed, and an attempt is made to understand how sexual differentiation may utilize and/or interact with trophic effects exerted by afferents and efferent targets. © 1994 Academic Press. All rights reserved.