Male songbirds use a versatile part of the brain to learn their father’s song during the early stages of development, according to a report published yesterday in the online version of Nature. Researchers at the University of California at San Francisco (UCSF) found that Bengalese finch males use a trial-and-error method in learning the song they will use to attract a mate once they reach maturity. The learning process begins around 40 days after hatching and ends about 90 days into development.
During their research, the neuroscientists focused primarily on the basal ganglia, a cluster of the brain known to be responsible for action selection, cognitive functions, and motor systems in birds and other animals. The brain structure is located at the base of the forebrain in humans and has been found to play a central role in neurological disorders including Parkinson’s disease, obsessive-compulsive disorder, and Tourette’s syndrome. One neurological model posits that the basal ganglia reinforces a behavioral pattern by transmitting a rewarding dopamine signal after receiving feedback on the result of the movement from the motor cortex.
“It’s the first place where the brain is putting two and two together,” said UCSF’s Jonathan Charlesworth, the first author of the report. “If you remove the basal ganglia in a bird that hasn’t yet learned to sing, it will never learn to do so.” Through previous research in the UCSF lab, neurologists were about to determine that adult finches can track the different notes in the song that that they play or hear and can modify them individually. The foundational experiments conducted in the lab of Michael Brainard, an associate professor of physiology at UCSF, showed that the adult finches could be trained to change notes in their song by emitting a harsh noise when a finch hit a particular note.
After a few hours of hearing these timed sonic disruptions, the finch would alter the pitch of the note associated with that noise. In the latest experiment, researchers sought to block signals sent from the basal ganglia to see if it would affect the finch’s ability to learn how to modify its song. They discovered that as long as the bird’s anterior forebrain pathway – a bundle of nerves between the basal ganglia and the motor cortex – was blocked, the birds could not change their song in accordance with the previous experiment’s negative stimulus.
The team then removed the block and found the finches were able to change the pitch of their song with no additional practice. It was as if they finches knew they wanted to change the particular note in their song, but couldn’t physically do it. “This study represents an important step in identifying brain mechanisms that mediate trial-and-error behavioral learning,” Richard Mooney, a neurobiologist at Duke University, told Nature News.
“It suggests that the basal ganglia can learn how to improve behavior even when they are prevented from changing it. This stands in contrast to the popular idea that the basal ganglia must actively drive variability for trial-and-error learning to occur.” Brainard expects this research to be extremely relevant to the efforts to treat and cure neurological disorders like Huntington’s or Parkinson’s disease.