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Dr. Farrah Madison, Biology

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In temperate zone species such as canaries (Serinus canaria) the neural circuitry regulating song behavior undergoes well-defined changes across the seasons. In males, increased daylengths in spring initiates an increase in gonadal volumes and circulating testosterone driving marked changes in brain morphology and song frequency. Females given exogenous testosterone in adulthood also demonstrate male-like changes in brain morphology and song behavior. More specifically, the telencephalic nucleus HVC (acronym is proper name), a key nucleus for song production, undergoes well-defined seasonal changes in neuroplasticity with a high rate of neurogenesis mediating marked changes in HVC volume. Much is known about the neural circuitry driving song behavior, however, the mechanisms underlying the morphological changes in adult hormone-modulated brain plasticity remain to be elucidated. Recently, perineuronal nets (PNN), extracellular matrix aggregations surrounding GABAergic interneurons, were shown to regulate afferent synaptic plasticity in the songbird brain. Moreover, we demonstrated that differential PNN expression could represent a key cellular mechanism mediating species variation in song behavior. In this study, we sought to investigate the density of PNNs in male and female canaries exposed to testosterone. Males were castrated and females were photoregressed and housed in our aviary on short days (8L:16D) for at least 6 weeks. Birds were surgically implanted with a 10 mm testosterone packed silastic implant or an empty implant as a control for 7 days. Brains were extracted, sectioned, and HVC volumes were quantified in Nissl stained sections. Brain sections were also double labeled via immunohistochemistry for parvalbumin and chondroitin. Both males and females treated with testosterone had larger HVC volumes compared to controls.


Title on poster differs from abstract booklet. Poster title: Perineuronal Net Expression in Adult-hormone Modulated Neuroplasticity (Serinus canaria)

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