Processing of Information by Auditory and Vestibular Hair Cells

The sense of hearing shows a truly remarkable ability to detect weak sounds amidst loud and competing environmental noise. This detection is enabled by hair cells, specialized cells that are responsive to mechanical movement below that of a nanometer. Prior work has shown that these cells are active – they expend energy to enhance their response. Secondly, they are not linear – they amplify weak signals and compress strong ones. Other studies have uncovered various cellular processes that contribute to the hair cell’s ability to sense a very weak signal. However, what is not known is how these very weak signals are differentiated from various noise sources, both within the biological system itself and the external environment. The investigators plan to measure the hair cell response to complex sounds, starting from pure tones and increasing complexity to mimic sounds that the animals would be detecting in nature. Information theory and other statistical methods will then be used to determine which classes of signals the cell is most responsive to. The investigators will also test how this response is degraded by the presence of noise. As a comparison, they will use hair cells both from an auditory organ, specialized for detecting animal calls and other air-borne signals, and from a vestibular organ, specialized for detecting ground-borne signals. This study explores how auditory and vestibular systems perform remarkably sensitive detection in the presence of noise and competing background signals. Analytical methods from the field of information theory will be adapted to study the graded response exhibited by mechanosensitive cells, with measurements obtained from sensory epithelia in vitro. Specifically, transfer entropy, Kolmogorov entropy, and mutual information will be applied to determine the degree of information extracted by sensory cells of the auditory and vestibular epithelia. The investigators will use semi-intact biological preparations of the inner ear, designed to maintain live and functional hair cells. External input of varying complexity, ranging from pure tones to transient pulses, as well as signals that mimic biologically relevant sound streams, will be applied to the cells. The goal of the study will be to determine whether there are classes of stimuli that optimize the information transfer. The robustness of the cellular response to noise and competing streams of information will be directly assessed by superposing these interfering signals onto the test stimuli and measuring the rate at which the information transfer is degraded. Computational models of the sensory cells will then be utilized to explain how the cells expend energy to perform computation, thus enabling the extraction of weak signals from the surrounding noise. 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. NSF Award ID: 2514506 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Dolores Bozovic | Institution: University of California-Los Angeles, LOS ANGELES, CA | Award Amount: $588,686 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2514506 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2514506.html