Major

Neuroscience

Anticipated Graduation Year

2020

Access Type

Open Access

Abstract

To allow animals to separate a complex sound into its frequency components, the auditory system is organized in tonotopy; neurons at various levels of the auditory pathway are topographically arranged by their responses to different sound frequencies. Disruption of tonotopy often results in auditory processing disorders and language learning disabilities. Despite its importance in auditory functions and clinical implications, almost nothing is known about how the tonotopic map is established during development. In this study, we use genetic approaches to label spiral ganglion neurons (SGNs) and their auditory nerve fibers with different characteristic frequencies respectively. We found that functionally distinct SGN populations employ different cellular strategies to target and innervate neurons in the cochlear nucleus during tonotopic map formation. Auditory nerve fibers with high characteristic frequencies (high-CF fibers) initially overshoot and sample a large area of different targets before refining their connections to correct targets, while fibers with low characteristic frequencies (low-CF fibers) are more accurate in initial targeting and undergo minimal target sampling. Additionally, compared to the high-CF fibers, a higher proportion of low-CF fibers terminate on bushy cells with multiple branching and smaller Endbulb of Held synapses. These observations reveal the diversity of cellular mechanisms that functionally distinct auditory neurons use to pick their targets during tonotopic map formation.

Faculty Mentors & Instructors

Wei-Ming Yu, Research Professor, Department of Biology

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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Spiral Ganglion Neurons with Distinct Preferred Frequency Response Employ Different Strategies to Innervate the Cochlear Nucleus

To allow animals to separate a complex sound into its frequency components, the auditory system is organized in tonotopy; neurons at various levels of the auditory pathway are topographically arranged by their responses to different sound frequencies. Disruption of tonotopy often results in auditory processing disorders and language learning disabilities. Despite its importance in auditory functions and clinical implications, almost nothing is known about how the tonotopic map is established during development. In this study, we use genetic approaches to label spiral ganglion neurons (SGNs) and their auditory nerve fibers with different characteristic frequencies respectively. We found that functionally distinct SGN populations employ different cellular strategies to target and innervate neurons in the cochlear nucleus during tonotopic map formation. Auditory nerve fibers with high characteristic frequencies (high-CF fibers) initially overshoot and sample a large area of different targets before refining their connections to correct targets, while fibers with low characteristic frequencies (low-CF fibers) are more accurate in initial targeting and undergo minimal target sampling. Additionally, compared to the high-CF fibers, a higher proportion of low-CF fibers terminate on bushy cells with multiple branching and smaller Endbulb of Held synapses. These observations reveal the diversity of cellular mechanisms that functionally distinct auditory neurons use to pick their targets during tonotopic map formation.