Ph.D. Research Proposal Exam: Mohsen Rezaeizadeh

Tuesday, February 4, 2020
11:00 a.m.
AVW 2224
Maria Hoo
301 405 3681
mch@umd.edu

ANNOUNCEMENT:  Ph.D. Ressearch Proposal Exam


Name: Mohsen Rezaeizadeh

 

Committee:
Professor Shihab Shamma (Chair)
Professor Jonathan Simon
Professor Behtash Babadi


Date/time:February 4/2020,  11:00 AM

 

Location: AVW 2224
 
Title: BINDING THE COMPONENTS OF A COMPLEX AUDITORY STREAM DURING SEGREGATION

  

Abstract:

Humans and other animals can segregate a targeted sound from background interference and noise with remarkable ease. It is hypothesized that attention is essential for this process to occur in a listener’s brain, and that the temporal coherence of the acoustic features of the target, and their incoherence from those of other sources, are the two key factors that induce the binding of the target features and its emergence as the foreground sound source. Specifically, the temporal coherence principle implies that acoustic features underlying the perceptual attributes of a sound emanating from a single source (e.g. its pitch, timbre, location, loudness) fluctuate coherently in power over time, and that the attentive listener tracks and utilizes this coherence to extract perceptually the source. This predicts that attentive listening induces (1) mutual excitatory influences among neurons responding to coherent features, hence causing them to mutually enhance their responses; and, by contrast, that (2) simultaneous mutual suppression would build up among incoherently responding neurons, causing them to diminish. In this study we test these predictions in human subjects by measuring EEG responses while they segregate streams of complex sounds ranging from simple harmonic and inharmonic tone complexes, to speech mixtures. To gain a view of the responses to individual frequency components in the mixtures, we exploited the modulatory effects of ongoing and persistent attention on the responses to a probe tone to measure the enhancement and suppression of the complex components while subjects were instructed to selectively attend to various target streams. We show that the response modulations are consistent with the predictions of temporal coherence and thus provide evidence for how the brain can online perceptually segregate complex mixtures, and hence enhance the ability of listeners to track target sounds despite severe noise and interference.

 

Audience: Faculty 

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