Lesions targeted to the anterior forebrain disrupt vocal variability associated with testosterone-induced sensorimotor song development in adult female canaries, Serinus canaria.

Abstract

Learned communication was a trait observed in a limited number of vertebrates such as humans but also songbirds (i.e., species in the suborder passeri sometimes called oscines). Robust male-biased sex-differences in song development and production have been observed in several songbird species. However, in some of these species treating adult females with testosterone (T) induced neuro-behavioral changes such that females become more male-like in brain and behavior. T-treatment in these adult females seemed to stimulate sensorimotor song development to facilitate song masculinization. In male songbirds it was known that the lateral magnocellular nucleus of the anterior nidopallium (LMAN) played a modulatory role during song development. LMAN was androgen sensitive and may be a key target of a T-induced recapitulation of a developmental process in adult females. This hypothesis was tested. Adult female canaries were given either a chemical lesion of LMAN or a control sham-surgery. Prior to surgery birds were individually housed for 2-weeks in sound-attenuated chambers to record baseline vocal behavior. Post-surgery birds were given 1-week to recover before subcutaneous implantation with silastic capsules filled with crystalline-T. Birds remained on treatment for 3-weeks (behavioral recordings continued throughout). Birds with a lesion to LMAN had less variability in their song compared with controls. The diversity of syllable and phrase type(s) was greater in sham controls as compared with birds with LMAN lesions. Birds did not differ in song rate. These data suggested that the sustention and conclusion of T-induced sensorimotor song development in adult female canaries required an intact LMAN.