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The Case of the Missing Pitch Templates: How Harmonic Templates Emerge in the Early Auditory System

dc.contributor.authorShamma, Shihaben_US
dc.contributor.authorKlein, David J.en_US
dc.description.abstractPeriodicity pitch is the most salient and important of all pitch percepts.Psycho-acoustical models of this percept have long postulated the existenceof internalized harmonic templates against which incoming resolved spectracan be compared, and pitch determined according to the best matchingtemplates cite{goldstein:pitch}. <p>However, it has been a mystery where andhow such harmonic templates can come about. Here we present a biologicallyplausible model for how such templates can form in the early stages of theauditory system. The model demonstrates that {it any} broadband stimulussuch as noise or random click trains, suffices for generating thetemplates, and that there is no need for any delay-lines, oscillators, orother neural temporal structures. <p>The model consists of two key stages:cochlear filtering followed by coincidence detection. The cochlear stageprovides responses analogous to those seen on the auditory-nerve andcochlear nucleus. Specifically, it performs moderately sharp frequencyanalysis via a filter-bank with tonotopically ordered center frequencies(CFs); the rectified and phase-locked filter responses are further enhancedtemporally to resemble the synchronized responses of cells in the cochlearnucleus. <p>The second stage is a matrix of coincidence detectors thatcompute the average pair-wise instantaneous correlation (or product)between responses from all CFs across the channels. Model simulations showthat for any broadband stimulus, high coincidences occur between cochlearchannels that are exactly harmonic distances apart. Accumulatingcoincidences over time results in the formation of harmonic templates forall fundamental frequencies in the phase-locking frequency range. <p>Themodel explains the critical role played by three subtle but importantfactors in cochlear function: the nonlinear transformations following thefiltering stage; the rapid phase-shifts of the traveling wave near itsresonance; and the spectral resolution of the cochlear filters. Finally, wediscuss the physiological correlates and location of such a process and itsresulting templates.en_US
dc.format.extent603623 bytes
dc.relation.ispartofseriesISR; TR 1999-27en_US
dc.subjectneural systemsen_US
dc.subjectsignal processingen_US
dc.subjectpitch detectionen_US
dc.subjectharmonic templatesen_US
dc.subjectauditory systemen_US
dc.subjectIntelligent Signal Processing and Communications Systemsen_US
dc.titleThe Case of the Missing Pitch Templates: How Harmonic Templates Emerge in the Early Auditory Systemen_US
dc.typeTechnical Reporten_US

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