Date of Completion

10-5-2017

Embargo Period

10-5-2017

Keywords

spike timing, temproal code, sound shape

Major Advisor

Dr. Heather Read

Co-Major Advisor

Dr. Monty Escabi

Associate Advisor

Dr. Ian Stevenson

Associate Advisor

Dr. Sabato Santaniello

Field of Study

Biomedical Engineering

Degree

Doctor of Philosophy

Open Access

Campus Access

Abstract

Mammals discriminate temporal “shape” cues in speech and other sounds but the underlying neural pathways and mechanisms remain a mystery. Shape cues include the rising and falling slopes and the duration of change in the sound envelope amplitude over time and are critical for sound perception. The auditory cortices are essential for behavioral discrimination of temporal cues and yet the neural mechanisms underlying this ability remain unknown. Primary (A1) and ventral non-primary auditory cortical fields (VAF & SRAF) are physiologically and anatomically organized and specialized to represent distinct spectral and spatial cues in sound. The current study investigates cortical field differences for encoding envelope shape in sound.

In the present study, we ask whether A1, VAF and SRAF could utilize spike rate, distinct temporal spiking patterns, including onset and sustained components, to discriminate sound shape. To address these questions we computed a discrimination index based on the spike distance metric. We find response durations and optimal time constants for discriminating sound shape increase in rank order with: A1 < VAF

To address the question of whether spike rate or spike timing contributes to this discrimination, a Naïve Bayes classifier was used to classify spike trains with varying sound shapes. In all three regions spike times resulted in significantly higher correct classification based on spike times than spike rates. Together, these results indicate that the three regions can discriminate sound shapes and that this ability stems from spike timing.

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