The birds three song-control regions are called the HVC, RA and X. All are located in the forebrain and grow quickly and in sequence. The brains of the birds were examined after 7 and 30 days, and the volume of the song production areas did not differ between the deafened and the hearing sparrows. Even though the deafened birds sang considerably less often, there was no degradation in the structure of their songs, according to Brenowitz.
Another major finding of the study is that seasonal growth of these song production areas of the brain does not require hearing or high levels of singing. This is surprising to a lot of people because many thought seasonal growth of song nuclei was related to the rate of singing, he said. While the research was conducted on birds, it also has potential long-term human applications, addressing the broad issue of environment enrichment supporting brain plasticity.
This study suggests that playing tapes of recorded speech to try to help a person recover language after a stroke might not be productive. But perhaps we could use neutrophins, growth-inducing proteins whose synthesis by brain neurons is stimulated by testosterone. In sparrows, brain areas are directly stimulated by these hormones to grow and one day such hormones might possibly help repair brain damage caused by strokes or neurodegenerative diseases, said Brenowitz.