Male canaries sang better mating songs after researchers applied testosterone to their entire brains, not just the part that controls sexual motivation, report researchers.
The findings may shed light on how testosterone and other anabolic steroids act in the human brain to regulate sexual behavior, speech, and other activity.
The male canary’s ability to sing a pitch-perfect song is integral to wooing and mating with a female. As seasons change, so does the song quality and frequency. The male sex hormone testosterone plays a role in this changing song behavior.
A team led by brain scientists from Johns Hopkins University tested whether testosterone was needed throughout the brain or just in one specific area: the medial preoptic nucleus. That site, called the POM, controls sexual motivation in many animals, including humans.
“In so many other species, testosterone in the POM can regulate an animal’s motivation, in this case, the motivation to sing,” says graduate student Beau Alward, the lead investigator on the project. “However, singing and courting a female is more than just motivation.
“Our data suggests that testosterone needs to act in different areas of the brain to regulate the specific components of this complex social phenomenon,” he says.
Alward and fellow researchers added testosterone into the POM of some male canaries and throughout the brains of others. A control group received no hormone treatment at all. They found that birds treated only in the POM sang more frequently than the controls, but could not produce the high-quality song most attractive to females.
But canaries that received testosterone throughout the brain sang frequent, high-quality songs, leading the researchers to conclude that the hormone acts on several different brain areas to regulate not only how much but also how well the birds could vocalize.
“The quality of the song that is required to successfully attract a mate and then the process of attending to the female, or singing to her, when she is there … requires the coordination of multiple brain regions,” Alward says.
The researchers say these results have broad implications for learning how steroid use in humans affects sexual behaviors and how hormones regulate the different components of human speech.
“The hormones in these birds are identical to those in humans and they can regulate brain changes in a similar manner,” says senior author Gregory F. Ball, professor of psychological and brain sciences.
The canary brain is considered a good model for brain study due to its ability to change its neural pathways and synapses in response to changes in behavior, the seasonal environment, and injury.
In the study, the researchers artificially replicated a springtime environment. The birds responded to the spring-like conditions with birdsong and mating behaviors as they normally would at that time of year.
Jacques Balthazart from the University of Liege in Belgium also contributed to the study, which appears in the Proceedings of the National Academy of Sciences. The National Institute of Neurological Disorders and Stroke supported the research.
Source: Johns Hopkins University