Cortical Representations of Harmonic and Virtual Pitch in Humans

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1 PROJECT SUMMARY/ABSTRACT 2 Pitch and harmonicity play a defining role in the perception of speech and music, and are crucial for 3 the perceptual organization of sounds in an auditory scene. Listeners with hearing loss, and 4 especially those with cochlear implants, suffer from a striking deficit in pitch perception abilities, as 5 current sound processing strategies are unable to provide robust pitch cues. Despite advances in our 6 understanding of how pitch is perceived, coded, and represented in our auditory system, there are 7 still significant gaps in our basic understanding of how pitch, and especially harmonicity, is 8 represented in the auditory cortex. A better understanding of the neural transformations involved in 9 pitch perception should help in designing more effective neural and acoustic prostheses. The overall 10 goal of the proposed project is to understand the neural representation of pitch and harmonicity and 11 elucidate the role of temporal integration in pitch perception using a combination of behavioral 12 (psychoacoustics), electrophysiology (EEG), and neuroimaging techniques (fMRI). In the mentored 13 K99 phase of this project, the candidate will conduct research on both of these overarching themes. 14 fMRI will be used to investigate what properties of harmonic complex tones are represented in 15 anterior-lateral regions of auditory cortex (Aim 1). Using carefully controlled stimuli, this study should 16 provide strong evidence for whether harmonic tones elicit a stronger response than inharmonic tones 17 in auditory cortex. The candidate will also conduct a series of behavioral experiments using a novel 18 stimulus that produces an illusory virtual pitch percept, to provide empirical data for quantifying the 19 parameters governing temporal integration in the perception of pitch (Aim 2). These behavioral 20 experiments will add crucial understanding of the temporal aspects of pitch perception, which are not 21 taken into account in current pitch perception models. In the R00 phase of the project, the candidate 22 will utilize the techniques and findings of Aims 1 and 2 to study two important aspects of pitch 23 processing and perception. A novel modification of the stimulus investigated in Aim 2 will be utilized in 24 an fMRI study to differentiate the cortical representations of different perceptual modes of listening, 25 namely synthetic and analytic. Additionally, this stimulus will also be used in an EEG study to explore 26 the neural correlates of the Pitch Onset Response (POR). Overall, this project will relate perceptual 27 characterizations of the illusory stimulus to neurophysiological findings to provide new insights to the 28 field of pitch perception, which in turn could motivate the development of novel pitch processing 29 strategies in auditory prostheses. The research performed and training provided during this award will 30 enable the candidate to achieve her goal of developing an independent research program that 31 employs both neurophysiological and behavioral approaches to investigate auditory phenomena.