Student Theses and Dissertations

Date of Award

2022

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

RU Laboratory

Vaziri Laboratory

Abstract

The neural evoke activity to pure tones in primary auditory cortex has been systematically studied for many years, as has the spatial organization of these responses. Unlike pure tones, natural sounds possess complex spectro-temporal structures across frequencies. How simple tuning properties scale across ensembles of neurons to represent more complex sensory environments is still a question of active investigation and debate. To better understand the coding principles used to represent complex auditory sounds, we performed 2-photon calcium imaging of neural activity of the entire auditory cortex in awake mice, while playing sounds composed of single or multiple frequencies. While we observed simple tuning in response to single frequency stimuli, the calcium responses to combinations of tones displayed characteristic nonlinearities. Moreover, we could not reconstruct the multi-tone response from the responses to the individual constituent tones alone. The subset of neurons most exhibiting such nonlinearities were found to perform certain fuzzy logic operations, on the input signal and were topographically organized across the auditory cortex. Such neurons increased the effective dimensionality of the sensory representation, enhancing the decodability and classification of complex stimuli. Together, our results reveal that the auditory cortex contains a topographical map of spatially-clustered computational ensembles able to detect specific combinations of spectral features. We further hypothesize that local non-linear computations such as these may contribute to high dimensional representation across different sensory modalities.

Comments

A Thesis Presented to the Faculty of The Rockefeller University in Partial Fulfillment of the Requirements for the degree of Doctor in Philosophy

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