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Explaining individual differences in noisy speech perception using multidimensional scaling of fMRI response patterns

Poster B79 in Poster Session B, Tuesday, October 24, 3:30 - 5:15 pm CEST, Espace Vieux-Port

Michael Beauchamp1, Yue Zhang2, Johannes Rennig3, John Magnotti1; 1University of Pennsylvania, 2Baylor College of Medicine, 3University of Tübingen

Humans have the unique ability to decode the rapid stream of language elements that constitute speech. Although auditory noise in the environment interferes with speech perception, perceivers can partially compensate using visual information from the face of the talker. However, individuals vary greatly in their ability to understand noisy audiovisual and auditory-only speech. BOLD fMRI was used to examine the neural correlates of individual differences in noisy speech perception. Thirty-seven participants were presented with speech in five formats: audiovisual speech with and without added auditory noise; auditory-only speech with and without noise; and visual-only speech, and reported the intelligibility of the speech with a button press. An event-related design was used to sort noisy speech trials by their intelligibility. Individual-differences multidimensional scaling was applied to the fMRI response patterns to create representational space from the patterns of activity in superior temporal cortex evoked by speech. The distance in representational space between intelligible and unintelligible noisy speech served as a neural index of intelligibility; separate indices were calculated for audiovisual and auditory-only speech. For every participant, the neural intelligibility index was greater for audiovisual speech than auditory-only speech, matching the greater perceptual intelligibility of noisy audiovisual compared with auditory-only speech. The neural index also predicted individual differences. Participants with larger neural indices were better able to understand noisy speech, a relationship that held for both auditory-only and audiovisual speech. Individual differences multidimensional scaling sheds light on the neural mechanisms for the well-documented improvement in noisy speech perception when the face of the talker is visible; and on the substantial individual differences observed across healthy individuals in their ability to perceive noisy speech. This knowledge may help in the development of strategies for helping those with impaired speech perception.

Topic Areas: Speech Perception, Methods

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