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Predicting developmental change in language processing via cortical thickness of the language network
Poster Session E, Friday, October 2, 11:00 am - 1:00 pm, Wangari Maathai
Noah Scott1, Hyoju Kim1, Ö. Ece Demir-Lira1, Bob McMurray1; 1University of Iowa
Language acquisition is a foundational aspect of child development. While prior research has examined the growth of linguistic knowledge, less work has investigated the development of online language processing. Spoken word recognition represents a critical component of this real-time processing in which listeners activate multiple lexical candidates that compete before settling on a target. This process is commonly studied using the Visual World Paradigm (VWP), in which participants hear a target word (e.g., “wizard”) while viewing images representing the target (e.g., a wizard) and phonologically similar competitors (e.g., a window and a whistle). During trials, fixations become concentrated on the target, while attention to phonological competitors (“cohorts”) diminishes. Children’s efficient resolution of this lexical competition has been associated with broader language abilities (McMurray et al., 2010), yet neural systems supporting real-time spoken word recognition remain poorly understood. This project examined the structural neural correlates of lexical competition and its development in an accelerated longitudinal sample of English-speaking children from grades 1–7. Principal component (PC) analysis of VWP fixations across grades yielded five components accounting for 80.5% variance. Growth curve models were used to estimate relationships between 4th-grade cortical thickness and developmental trajectories of each component. Based on Hickok and Poeppel’s (2007) dual pathway model, we hypothesized that cortical areas along the more cognitively direct ventral stream would support early activation of words, while areas within the more motor/attention-related dorsal stream would support resolution of lexical competition. PC1 (20.5% variance) was a general component reflecting both late and early aspects of lexical processing. We had no specific hypotheses relating it to the brain, and there were no significant relationships to language pathways. PC2 (19.5%) reflected faster accumulation of fixations to task-relevant images and was hypothesized to relate to ventral language regions. Supporting this prediction, lower lateral STG and orbital IFG thickness were associated with greater positive PC2 development (STG: b=-0.06, p=.027; IFG orbitalis: b=-0.06, p=.049). PC3 (15.2%) and PC4 (13.3%) indexed different aspects of the resolution of lexical competition: PC3 reflected the rate of cohort suppression, whereas PC4 reflected a tradeoff between slower suppression and greater ultimate competition resolution. We hypothesized that these components would relate to dorsal language regions. This prediction was supported for PC4, but not PC3. SMG thickness positively predicted PC4 (b=0.34, p=.012), and PoCG thickness negatively predicted PC4 (b=-0.26, p=.022). Although PC3 was not predicted by dorsal regions, greater ventral MTG thickness predicted stronger linear development of PC3 (b=0.10, p=.033). Exploratory analyses further showed that PC5 (11.9%), reflecting overall fixation quantity, was positively associated with a higher early-to-late dorsal pathway thickness ratio (b=0.16, p=.026). These findings demonstrate that the structure of neural architecture relates to the development of language processing. They suggest that, contrary to our expectations, ventral semantic regions may not only support lexical activation, but also competitor suppression dynamics. Dorsal phonological/motor regions, however, may support competition resolution, consistent with expectations. This work illustrates how the significance of cortical thickness may vary across cortical regions for different dimensions of the same cognitive process.
Topic Areas: Language Development/Acquisition, Speech Perception