Timing of brain-derived neurotrophic factor exposure affects life expectancy of new neurons.

The high vocal center (HVC) of adult male canaries, Serinus canaria, is necessary for the production of learned song. New neurons are added to HVC every day, where they replace older neurons that have died, but the length of their survival depends on the time of year when they are born. A great number of HVC neurons born in the fall, when adult canaries learn a new song, are still present 8 mo later, when this song is used during the breeding season.

Gonads and singing play separate, additive roles in new neuron recruitment in adult canary brain.

New neurons are constantly added to the high vocal center (HVC) of adult male canaries, Serinus canaria. Singing and testosterone (T) are known to promote this addition, but it is not known whether either variable can act on its own and what is their effect when acting together. We studied this question by castrating adult male canaries in late summer and quantifying their song in early fall.