CIE Seminar Series 2018: Pleiotropic effects of testosterone on a sexually selected trait: birdsong

SPEAKER: Prof Gregory F. Ball, Dean, College of Behavioral and Social Sciences, University of Maryland, College Park, MD, USA

DATE: Friday, 20th July 2018

TIME: 1:30pm

LOCATION: Geelong Campus at Waurn Ponds – room ka4.207 (green room)

Seminar will also be video linked to the following campuses: Melbourne Campus at Burwood –Burwood Corporate Centre and Warrnambool Campus, Room J2.19 (Fishbowl room)

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ABSTRACT. The functions of birdsong include the ability to attract males and/or to repel competitors.  It is therefore not surprising that, in males in the temperate zone especially, birdsong is often produced in the context of reproduction.  Testosterone of gonadal origin increases during the reproductive phase of the annual cycle and can significantly influence song production as well as song development via effects on song crystallization (testosterone secretion at the time of sexual maturity is essential for full crystallization to occur).   The widespread distribution of androgen receptors in the song control system, the syrinx as well as in the diencephalon and the midbrain raises questions as to where and how testosterone is exerting its myriad effects on song.  By selectively implanting testosterone into select brain regions of castrated male canaries (Serinus canaria) we have identified the medial preoptic area as a critical site for the induction of a generalized increase in sexual motivation that includes the motivation to sing.  Testosterone action in the forebrain song nucleus HVC in contrast facilitates song stereotypy.  Canaries receiving testosterone in the preoptic area and HVC sing stereotypic songs but at a much lower amplitude indicating that testosterone effects on amplitude are regulated elsewhere in the brain or the periphery.  We also treated male canaries with bicalutamide, an androgen-receptor antagonist that does not cross the blood-brain barrier. Thus, we isolated androgen action to the periphery in order to target the syrinx, the avian vocal production organ. Bicalutamide treatment reduced song complexity but not song acoustic stereotypy. Bicalutamide-treated birds also exhibited reduced performance of “special trills” and disrupted special syllable morphology. The performance and complexity of special trills in particular are able to stimulate copulation solicitation displays in female canaries to a substantially higher degree than any other component of canary song. The bilateral implantation of the potent androgen receptor antagonist flutamide in two key brain regions the motor cortical-like brain region–the robust nucleus of the arcopallium (RA) and HVC revealed that androgen in RA controls syllable and trill bandwidth stereotypy, while not significantly affecting higher order features of song such syllable-type usage (i.e., how many times each syllable type is used) or syllable sequences. In contrast, androgen signaling in HVC controls song variability by increasing the variability of syllable-type usage and syllable sequences, while having no effect on syllable or trill bandwidth stereotypy. Other aspects of song, such as the duration of trills and the number of syllables per song, were also differentially affected by androgen signaling in HVC versus RA. Overall, these results highlight the pleiotropic function of steroid hormones in coordinating distinct features of a single behavior into an adaptive behavioral response, and suggest that selection may shape the expression of sexual-selected traits by linking their expression to androgen receptor activation in relevant brain sites and peripheral organs.

BIO. Gregory F. Ball joined the University of Maryland in 2014 as Professor and Dean of the College of Behavioral and Social Science. He was previously Professor and Vice Dean for Science and Research in the Krieger School of Arts and Sciences at Johns Hopkins University where he directed the undergraduate neuroscience program. Dr. Ball holds a Ph.D. in psychobiology from the Institute of Animal Behavior at Rutgers University; Colin Beer served as his advisor. He completed his postdoctoral work at Rockefeller University where he worked with John Wingfield and Peter Marler.  Dr. Ball’s lab is interested in the interrelation of hormones, brain, and behavior. He studies a variety of avian species including songbirds and Japanese quail that exhibit high degrees of neuroplasticity across the seasons and in response to hormone treatment. His works concerns hormone effects on both affective and cognitive aspects of vocal communication.  He studies how hormones modulate song production and how the perception of song along with other environmental cues modulates the timing of reproduction in birds.  He is a fellow of the American Psychological Association, American Psychology Society, the American Ornithologists’ Union and the American Association for the Advancement of Science.

Appointments with guest speaker may be made via kate.buchanan@@deakin.edu.au

For more information on the speaker, please go to https://bsos.umd.edu/facultyprofile/ball/gregory