The University of Chicago’dan Dr. Arij Daou 26 Mart 2015 Perşembe günü saat 14:00'de Mühendislik ve Doğa Bilimleri Fakültesi Toplantı Salonu’nda (D Blok, 4. Kat) seminer verdi.
Electrophysiological characterization, temporal precision and sequence generation in HVC neurons of the songbird.
Understanding how neural sequences are learned and propagated to generate ongoing behavior is a fundamental problem in neuroscience. Neurons in the zebra finch song system nucleus HVC play a crucial role in song learning and production. Electrophysiological characterization of component HVC neurons is an important requirement in understanding the HVC function. The nucleus HVC contains three neural populations: neurons that project to the RA (robust nucleus of arcopallium), neurons that project to Area X (of the avian basal ganglia), and interneurons. These three populations are interconnected with specific patterns of excitatory and inhibitory connectivity. How HVC neurons interact to elicit learning and vocalization, how precise timing is achieved, and how sequences are sustained in network properties remain open questions. We first performed whole cell current-clamp recordings on HVC neurons within brain slices to examine their intrinsic firing properties and determine which ionic currents are responsible for their characteristic firing patterns. We also developed conductance-based models for the different neurons and calibrated the models using data from our brain slice work. These models were then used to generate predictions about the makeup of the ionic currents that are responsible for the different responses to stimuli. These predictions were then tested and verified in the slice using pharmacological manipulations. The model and the slice work highlight roles of a hyperpolarization-activated inward current (Ih), a low-threshold T-type calcium current (ICa-T), an A-type potassium current (IA), a calcium-activated potassium current (ISK), and a sodium-dependent potassium current (IKNa) in driving the characteristic neural patterns observed in the three HVC neuronal populations. Next, we carried out intracellular recordings of HVC neurons in singing zebra finches. We show that individual HVCRAneurons produce bursts at a single, precise time during each rendition of the song. Our results provide insight into the fundamental mechanisms by which neural circuits can generate complex sequential behaviors.
Biography:
I'm a post-doctoral researcher at the Neuroscience department of the University of Chicago and interested in exploring neural sequence generation and the temporal precision that neurons in specific regions of the brain (like the HVC of the songbird) exhibit during specific complex motor behaviors (like song production). This ability of the brain to generate temporally precise and stereotyped neural activity is the backbone of most of the complex tasks that underlies our everyday life such as speech, playing musical instruments, etc, yet despite its fundamental importance, very little is known about it neurobiological underpinnings. To approach this problem, I use in vivo and in vitro whole-cell recordings from identified neurons in conjunction with pharmacology and microstimulation. In addition to that, my work draws as needed from a set of computational and physiological techniques including single and multiunit extracellular recordings, immunohistochemistry, neuro-anatomy, mathematical modeling and software development.
During my graduate life at FSU, I worked with Richard Bertram on mathematical modeling and I trained in the labs of Frank Johnson and Richard Hyson to carry out the various experimental techniques. I took my PhD from FSU in August 2013. I also have a Bachelor’s degree in Computer Science and Biology from the American University of Beirut.
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