Browsing by Subject "Songbird"
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Item Open Access A Pathway from the Midbrain to the Striatum is Critical to Multiple Forms of Vocal Learning and Modification in the Songbird(2017) Hisey, ErinMany of the skills we value most as humans, such as speech and learning to play musical instruments, are learned in the absence of external reinforcement. However, the model systems most commonly used to study motor learning employ learning paradigms in which animals perform behaviors in response to external rewards or punishments. Here I use the zebra finch, an Australian songbird that can learn its song as a juvenile in the absence of external reinforcement as well as modify its song in response to external cues as an adult, to study the circuit mechanisms underlying both internally and externally reinforced forms of learning. Using a combination of intersectional genetic and microdialysis techniques, I show that a striatonigral pathway and its downstream effectors, namely D1-type dopamine receptors, are necessary for both internally reinforced juvenile learning and externally reinforced adult learning, as wells as for song modification in response to social cues or to deafening. In addition, I employ optogenetic stimulation during singing to demonstrate that this striatonigral projection is sufficient to drive learning. Interestingly, I find that neither the striatonigral pathway nor D1-type dopamine receptors are necessary for recovery of pitch after externally driven pitch learning. In all, I establish that a common mechanism underlies both internally and externally reinforced vocal learning.
Item Open Access Developing Molecular Tools for Interrogating a Vocal Learning Avian Species(2020) Biegler, Matthew TheodorThe zebra finch, an Australian songbird, is a uniquely powerful model organism for the study of vocal production learning, and its song system shares behavioral, anatomical, and genetic properties with the human spoken language circuit. However, research in zebra finches are disadvantaged by the lack of proper tools and techniques for tractable investigation of the molecular underpinnings of vocal learning. Here, I worked to close the gap in three areas. First, I induced a continuous zebra finch cell line capable of monoclonal cell line generation for in vitro characterization and testing in zebra finch cells. Second, I utilized advanced methods to improve the descriptive cellular resolution of several genes with specialized expression in the song system that are convergent with humans and I tested genome editing tools in vivo to demonstrate the potential for their gene ablation in the zebra finch. Third, I modified transgenic techniques used in poultry toward the more efficient and versatile generation of transgenic songbirds. Finally, I used an in situ hybridization method I modified on the NR4A2 gene to validate avian brain organization hypothesis of Jarvis et al., 2013. This work provides new avenues for exploring avian biology and progress towards a more genetically tractable model system for songbird neuroscience.
Item Open Access Disrupting FoxP2 Expression Alters Song Variability and Signal Propagation Through a Basal Ganglia Pathway Important for Learned Vocalizations(2013) Murugan, MalavikaMutations of the FOXP2 gene impair speech and language development in humans and shRNA-mediated suppression of the avian orthologue FoxP2 disrupts song learning in juvenile zebra finches. How diminished FoxP2 levels affect vocal control and alter the function of neural circuits important to learned vocalizations remains unclear. Using a combination of behavioral analysis, in vivo intracellular recordings in anaesthetized birds, pharmacology and extracellular recordings in singing birds, I addressed how FoxP2 knockdown in songbird striatum affects vocal control and signal propagation through circuits important for the control of learned vocalizations. In summary, I found that FoxP2 knockdown in the songbird striatum disrupts developmental and social modulation of song variability. Recordings in anaesthetized birds show that FoxP2 knockdown interferes with D1R-dependent modulation of activity propagation in a corticostriatal pathway important to song variability, an effect that may be partly attributable to reduced D1R and DARPP-32 protein levels. Furthermore, recordings in singing birds reveal that FoxP2 knockdown prevents social modulation of singing-related activity in this pathway. These findings show that reduced FoxP2 levels interfere with the dopaminergic modulation of vocal variability, which may impede song and speech development by disrupting reinforcement learning mechanisms.
Item Open Access Estrogen’s Impact on the Specialized Transcriptome, Brain, and Vocal Learning Behavior of a Sexually Dimorphic Songbird(2020) Choe, Ha NaThe song system of the zebra finch (Taeniopygia guttata) is highly sexually dimorphic, where only males develop the neural structures necessary to learn and produce learned vocalizations in adulthood. During early development, both males and females begin to develop their song system in a monomorphic manner, which diverges shortly after the onset of a critical sensory learning phase and results in reduced cell survival and proliferation in females, and accelerated cell proliferation in males. Estrogen has long been known to be involved in coordinating sexual development of the perinatal brain and nestling female zebra finches treated with estrogen do not exhibit this female-specific atrophy of the song system. How estrogen influences the development of the song system, and what it is doing at the molecular level has not been examined utilizing current generation sequencing technology.
In this dissertation, I tested whether estrogen manipulation impacts the transcriptomic profiles of telencephalic song learning nuclei in males and females. I treated animals with either vehicle, exemestane (an estrogen synthesis inhibitor), or 17-β-estradiol from the moment of hatching until time of sacrifice. I collected the song learning nuclei and their surrounding brain regions during the onset of sensory motor learning for transcriptomic analysis or during adulthood after collecting behavior. I found that of the 4 telencephalic song nuclei examined during the onset of the sensorimotor learning period at post hatch day 30, Area X was the most sexually dimorphic and the most impacted by estrogen administration. HVC was less sexually dimorphic and less impacted by estrogen manipulation. RA and LMAN had limited sexually dimorphic features, with little impact on their transcriptomes with estrogen manipulation. Additionally, I found that chronic estrogen depletion in males delayed male specific plumage development and resulted in impaired song learning. This supports the notion that while estrogen is sufficient in preventing atrophy of the song system in female zebra finches, it is not necessary for the gross development in males and may instead refine normal song development.
Item Open Access Neural Dynamics in the Basal Ganglia Underlying Birdsong Practice and Performance(2021) Singh Alvarado, JonnathanSkilled movements are typically more variable during practice, promoting exploration, yet highly stereotyped during performance, favoring exploitation. How neurons encode and dynamically regulate motor variability across practice and performance states remains unknown. Songbirds sing more variable songs when practicing alone and highly stereotyped songs when performing to a female, providing a powerful system to explore how neural ensembles regulate motor variability. Here, I used this system to identify neural mechanisms underlying practice and performance. First, I used deep brain imaging techniques to demonstrate that spiny neurons (SNs) in the basal ganglia (BG) encode vocal variability during solo practice, and that SN activity is strongly suppressed to enable stereotyped song performance towards a female. Second, I showed that optogenetically inhibiting SNs reduces pitch variability to female-directed levels. Third, I collaborated with Dr. John Pearson’s lab to uncover a coding scheme whereby specific patterns of SN activity map onto distinct spectral variants of syllables during vocal practice. Lastly, I use photometry, anatomical tracing, molecular profiling, and ex vivo physiology to establish that adrenergic signaling in the BG regulates vocal variability by directly suppressing SN activity. I conclude that SN ensembles encode and drive vocal exploration during practice, and the social context-dependent noradrenergic regulation of SN activity enables stereotyped and highly precise vocal performance.