Psychological and Brain Sciences Brown Bag Seminar: McCall Sarrett, Neuroscience Program
Psychological and Brain Sciences Departmental Brown Bag Seminar
McCall Sarrett, Neuroscience Program, The University of Iowa
“To /b/ or not to /b/: Characterizing the timecourse of speech perception”
Abstract: Understanding spoken language requires rapid analysis of incoming information at multiple levels. Perceptual analysis may be influenced by top down information to facilitate processing. Two experiments using electroencephalography (EEG) asked how listeners (N=31 and N=33, respectively) use top down expectations during processing of a target word that belongs to a Voice Onset Time (VOT) continuum (i.e. bees/peas). Expectations were set either via a sentence context (i.e. Honey is made by—b/peas; Experiment 1) or via a visual prime (i.e. a picture of bees; Experiment 2) which biased interpretation to one side of the continuum. We used a linear mixed model every 2 msec after target word onset to determine when different experimental factors affect the neural signal over time. Our results indicate: (1) extended representations of the raw VOT last over 500 msec, which may allow for more flexible language processing; (2) semantic integration happens early, and lasts longer when a word is embedded in a sentential context than when expectations are set by a picture; and (3) encoding of VOT, in limited cases, may be influenced by prior expectations, consistent with predictive coding accounts. Finally, we explore the cortical structures underlying some of these computations using electrocorticography (ECoG), in collaboration with the Department of Neurosurgery.