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The process by which baby birds learn to sing shares a number of traits with that by which toddlers learn to talk. Now researchers have identified a common gene between birds and people that underlies both abilities. The discovery marks the start of an effort to explore the genetic underpinnings of vocal learning.
Vocal learning is characteristic of a number of animals, including humans, dolphins, whales and birds. To probe how genetics guides this process, Sebastian Haesler of the Max Planck Institute for Molecular Genetics in Berlin and Kazuhiro Wada of Duke University Medical Center and their colleagues focused on a gene known as FoxP2, mutatation of which is associated with language problems in people. "In affected humans, the mutation causes a very specific dysfunction," study co-author Erich Jarvis of Duke University explains. "These people have largely normal motor coordination, but an inability to correctly pronounce words or form them into grammatically correct sentences. What¿s more, they have trouble understanding complex language." The team analyzed expression of FoxP2 in a number of bird species, both vocal learners and nonlearners, and in crocodiles, the closest living relative of birds.
In both humans and birds the gene is expressed in a brain region known as the basal ganglia, the researchers report today in the Journal of Neuroscience. "We found that the levels of FoxP2 seem to be increasing at times just before the bird begins to change its songs," Jarvis says. "So this is consistent with a cause-and-effect role, in which the gene switches on, allowing the song-learning circuitry to become more plastic, which allows the birds to imitate sounds." In nonvocal-learning species, in contrast, the team did not observe any localization or differential levels of FoxP2 activity. The team next plans to investigate whether there are small FoxP2 sequence differences between birds that learn to sing and those that do not, and study how mutations to the gene affect vocal learning. Other factors, such as connections between the brain and motor neurons controlling the voice, also contribute to vocal learning. But it is intriguing, Jarvis notes, "that an ancient gene like FoxP2 appears to have something to do with learned vocalizations both in humans and in birds."