Steroid Hormones Regulate Learned Vocal Communication Signals
Behavioral neuroscientists have long assumed that steroid hormones regulate behavior in a rather crude “on-off” manner. Such hormones are well known to affect general motivation, but they have not been thought to regulate complex behavior in a specific manner. New research led by the University of Maryland Department of Psychology, published in the Journal of Neuroscience, questions this assumption as it finds very specific and localized effects of steroids on learned song behavior in cortical-like brain regions of canaries.
Researchers—including Gregory Ball, Dean of the College of Behavioral and Social Sciences—investigated the effects of testosterone on birdsong in two distinct regions of the canary brain that resemble the human motor cortex. Songbirds develop the ability to produce complex songs in a manner similar to the way humans learn language. By blocking testosterone receptors in the key brain regions involved in singing, the research team was able to pinpoint a very specific role for sex hormones in the regulation of birdsong.
“It is already well understood that testosterone plays a prominent role in increasing a bird’s motivation to sing. However, our findings demonstrate that the role of hormones in regulating birdsong is much more complex and precise than previously thought,” said Dean Ball, also a professor of psychology. “They affect specific features of song such as the sequence and structure of certain sounds (trill), as well as the distinct syllables that constitute birdsongs.”
Canaries form a new song in the fall that becomes stable during the spring breeding season, when testosterone levels are high. In many ways, this process parallels vocal development in humans, which begins with babbling in the first months of life and stabilizes after puberty. These results suggest that testosterone contributes to the canary’s ability to not only affect the probability of singing but also produce a new learned song in adulthood.
Beau Alward, a former post-doctoral research scholar at UMD who now works at Stanford University, led the study. Dean Ball and Jacques Balthazart, from the University of Liege in Belgium, were contributing authors.