A right mixture of testosterone can make healthy brain changes and a new study sheds light on how testosterone acts in the human brain to regulate speech and could help explain how anabolic steroids affect human behaviours.
Singing and courting a female canary is more than just motivation. What's needed is a right mix of testosterone.
Researchers at the Johns Hopkins University have found that introducing testosterone in select areas of a male canary's brain can affect its ability to successfully attract and mate with a female through birdsong.
They also found that enhancing song activity based on testosterone in one brain area can change the size of a separate brain area that regulates song quality.
To determine how testosterone influences birdsong, lead author Beau Alward and senior author Gregory F Ball of the John Hopkins University divided 20 canaries into three groups to receive a hormone implant.
One group received the testosterone injection in a specific area of the brain called the medial preoptic nucleus - or POM - that controls sexual motivation in several animals as well as in humans.
The second group was given testosterone that acted throughout the brain. A third group received no hormone treatment at all, said the study published in the journal Proceedings of the National Academy of Sciences.
The birds that only received testosterone to the POM area sang at high rates but could not produce high-quality song that can attract females.
Meanwhile, canaries that received testosterone throughout the brain sang high-quality birdsong - consistent with the idea that the hormone acts on several different brain areas to regulate how much and how well the birds can sing.
"Our data suggests that testosterone needs to act in different areas of the brain to regulate the specific components of this complex social phenomenon. It appears that, like in so many other species, testosterone in the POM can regulate an animal's motivation, in this case, the motivation to sing," said Alward.
The researchers say these results have broad implications for research concerning how steroid use in humans affect sexual behaviours and how hormones regulate the difference components of speech in humans.
"The hormones in these birds are identical to those in humans and they can regulate brain changes in a similar manner," said Ball.
These findings could also shed light on how testosterone acts in the human brain to regulate speech or help explain how anabolic steroids affect human behaviours, the study concluded.