RUI: Structural and Dynamical Specializations of Axons that Enhance Neural Coincidence Detection

Swarthmore College, Swarthmore PA

Investigators

Abstract

Highly specialized cells process and transmit information throughout the brain. This project aims to develop mathematical models and theory to illuminate how neurons in the auditory system process sounds with exquisite temporal precision. Using an original modeling framework that allows systematic and parametric control of spike-generating regions of neurons, the project will explore relations between structure, dynamics, and function in an important stage of auditory processing: neurons in the auditory brainstem that encode the spatial locations of sound sources. These neurons are coincidence detectors – they are sensitive to the timing of inputs and respond maximally to inputs that arrive with near simultaneity. One prong of the research contributes to the advancement of public health by considering how pathological changes in neuron structure may degrade temporal processing in individuals with hearing loss. An essential component of the project is the mathematical and scientific training of undergraduate students. Students will engage in unique summer research experiences, gain knowledge working at the interface of mathematics and neuroscience, and contribute to a vibrant research environment at an undergraduate-only institution. The project develops new mathematical approaches to modeling of neural coincidence detection. The first objective is to develop multi-compartment models of soma-to-axon coupling to quantify how coincidence detection sensitivity may be enhanced in neural structures with multiple sites of spike generation along the axon. The focus will be on creating low-dimensional models (with few spatial compartments) that preserve essential dynamical properties of these neurons and that elucidate how the site of spike initiation enhances coincidence detection sensitivity. The second objective is to dissect the dynamical mechanisms by which neurons process temporal information in high-frequency signals. The focus here will be on coincidence detector neurons in the brainstems of birds. These neurons respond to inputs that generate small amplitude voltage oscillations at kilohertz-scale frequencies. The goal of this work is to develop novel mathematical theory to account for how neurons extract temporal information from oscillations at speeds similar to, or faster than, intrinsic neuronal time-scales. The third objective is to assess (with simulations) how pathological changes to axon structure during hearing loss may degrade coincidence detection sensitivity in the case of "electric hearing" with cochlear implants. By investigating neural coincidence detection in a variety of contexts, the project will contribute to the general understanding of nonlinear neural dynamics and temporal processing in neural circuits. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.