Adult female and male zebra finches show distinct patterns of spine deficits in an auditory area and in the song system when reared without exposure to normal adult song.

Male songbirds typically require exposure to normal adult conspecific song during development in order to learn a normal song of their own. Females require exposure to conspecific song during development in order to select high-quality, learned song over the incomplete song produced by males reared in isolation. Altering males' opportunity for song learning during development affects the neuroanatomy of brain regions involved in song production (the song system), but in females the neural effects of song learning are unknown. We raised male and female zebra finches (Taeniopygia guttata) with differing amounts of exposure to singing males during development. At 120 days, we Golgi-stained their brains and measured the frequency of dendritic spines in brain areas used in song perception or production. We found that females reared with little or no exposure to song have 31% fewer dendritic spines per unit length of dendrite in caudomedial nidopallium (NCM), a brain area activated by song perception, compared to control females. The deprived females had small deficits in the frequency of spines in HVC, a region activated by song production in males. Males with limited exposure to song had a 24% lower spine density in HVC than controls but only a 10% lower density in NCM. These data support the hypothesis that NCM is important in auditory learning, while HVC is involved in sensorimotor learning, and that these capacities are differentially emphasized in the two sexes.