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Mismatch Negativity Responses to Speech Contrasts in Adults With and Without Developmental Language Disorder
Poster Session E, Sunday, September 14, 11:00 am - 12:30 pm, Field House
This poster is part of the Sandbox Series.
Ali Solbi1, F. Sayako Earle1; 1University of Delaware
Developmental Language Disorder (DLD) is a neurodevelopmental disorder where individuals have ongoing difficulties with learning and using language, even though their hearing and intelligence are within normal limits and there is no obvious brain injury. While DLD has been widely studied in children, much less is known about how it affects adults, especially in how they process native speech sounds at the brain level. Understanding speech processing in adults with DLD is important because language difficulties often persist into adulthood and can impact education, employment, and social communication. Mismatch negativity (MMN), a component of event-related potentials (ERPs), is a useful tool for studying how the brain automatically detects changes in sounds. In this study, we measured MMN responses to native speech sound contrasts in adults with and without DLD to investigate possible differences in their brain processing of speech. We are recruiting participants into two groups. Thus far we have 45 typically developing (TD) adults and 10 adults with DLD. DLD classification was based on a combination of language history, and the methods described by Fidler et al., (2011, 2013; modified token task and spelling performance entered into an equation derived from a discriminant function). . EEG data were recorded, using a 32-channel ActiChamp system. MMN was measured in response to within-category (e.g. /bu1/ vs. /bu2/) and between-category (/bu/ and /gu/) English speech sound contrasts presented in an oddball paradigm. ERP responses were analyzed in two time windows: MMN (100–250 ms) and LDN (300–550 ms), across 29 scalp electrodes. Results from linear mixed-effects models showed that, for MMN, there was a significant main effect of speech sound Type, indicating stronger responses to between-category contrasts compared to within-category contrasts. However, there was no significant effect of Group (DLD vs. TD) and no significant Group × Type interaction for MMN, suggesting that both groups detected speech sound changes similarly in the early time window. In contrast, LDN results revealed both a significant main effect of speech sound type and a significant Group × Type interaction. Specifically, TD adults showed larger MMN responses to between-category contrasts compared to within-category contrasts, while adults with DLD showed a reduced differentiation between the two types of contrasts. To further explore these group differences, paired-sample t-tests were conducted separately for each group. The TD group showed a significant difference between within- and between-category contrasts, reflecting strong sensitivity to speech sound differences. In contrast, the DLD group did not show a significant difference, suggesting reduced or absent sensitivity to speech contrasts at this later stage of processing. While we are still in the process of recruiting for our DLD sample, this study shows that adults with DLD exhibit reduced neural sensitivity to speech sound contrasts compared to typically developing adults. While typically developing adults showed significantly stronger MMN responses to between-category than within-category contrasts, adults with DLD showed no significant difference between the two. These findings suggest that difficulties in discriminating phonological categories persist into adulthood in DLD, potentially contributing to ongoing language challenges.
Topic Areas: Disorders: Developmental, Speech Perception