BioE PhD Thesis Defense Presentation- Daniel Porto

Committee:       
Dr. Hang Lu, Chair (ChBE)
Dr. Patrick McGrath (Biology)
Dr. Robert Butera (ECE)
Dr. Lena Ting (BME, Emory)
Dr. Gordon Berman (Biology, Emory)

All animals constantly process sensory information from the environment to optimize behavioral responses. A fundamental question in neuroscience is how does the nervous system use neuronal circuits to calculate appropriate outputs from a given input, or in terms of systems analysis, what are transfer functions that describe this system’s function? A key challenge in answering this question is the overwhelming complexity of the nervous system. There are also several technical challenges that limit the acquisition of measurements of neuronal activity and behavioral outputs while simultaneously probing parts of the circuit. Caenorhabditis elegans serves as a useful model organism in answering questions about neural circuitry by addressing and overcoming both these issues. First, the C. elegans’ nervous system contains only 302 neurons and is the only organism that has a mapped connectome. Second, advancements in genetic manipulations and experimental techniques have enabled optical physiology in specific neurons, with optical measurements of neuronal activity using fluorescent reagents and optical probing of neuronal activity using optogenetics. This thesis focuses on the development of several integrated platforms to perform optical interrogation of various aspects of the nervous system, using image processing techniques and microscopy tools to improve throughput and robustness of both experimentation and analysis. These platforms were implemented to address specific biological questions, and were used in experiments involving phenotyping morphology, measuring neuronal activity using functional imaging, activation of excitable cells using optogenetics, and behavior tracking using image processing techniques. Using these platforms, I systematically inspected the mechanosensation circuit in C. elegans, using white noise analysis to estimate of impulse responses that characterize the neural circuitry, providing accurate models of its function. In addition, I applied the developed techniques to address other limitations in C. elegans research, including robust calcium imaging analysis in microfluidic devices, a high-throughput screen for a spinal muscular atrophy model, and FRET imaging in freely moving animals.