Integration of Ectopic Neurons into Motor Circuits

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Animal behavior is driven by interconnected circuits of nerve cells in the brain and the spinal cord. Although diversification of these networks through evolutionary history has led to the incredible range of behaviors we observe in animals today, little work has been done to address the fundamental question: How do neural circuits evolve? One way in which neural circuits may change is through the addition of new nerve cells to the brain and their subsequent incorporation into functional networks. This research uses the startle neural circuit of fish to explore the effects of adding new nerve cells to circuits. The startle circuit is advantageous to use as a case study for examining mechanisms for changing circuits because it includes relatively few and easily identified nerve cells and controls a discrete and well-described behavior. New startle neurons will be genetically introduced into the hindbrain. Physiological recordings and laser ablation techniques will be used to examine the role specific cells play in the animal?s behavior. It is hypothesized that while new nerve cells make some connections into preexisting circuits other connections will be restricted and that redundancy of function within circuits may act to mask aberrant nerve cell activity, preventing it from disrupting behaviors. By investigating how new nerve cells integrate into simple neural circuits in the brain, this research will provide a case study for understanding principles by which circuits may be modified through evolution and insight into the flexibility for and constraints on such changes. The broader impact of this proposal includes outreach to middle school girls in disadvantaged areas of the south side of Chicago through activities in schools and in the research laboratory. In addition, this proposed research will involve undergraduates and graduate students, providing opportunities for training in a diverse array of scientific approaches and methodologies.