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Neural activity associated with learning to articulate pseudowords in children with developmental language disorder
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Poster B65 in Poster Session B, Tuesday, October 24, 3:30 - 5:15 pm CEST, Espace Vieux-Port
Nilgoun Bahar1, Gabriel J. Cler2, Saloni Krishnan3,4, Kate E. Watkins1,4; 1Welcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, University of Oxford, UK , 2Department of Speech & Hearing Sciences, University of Washington, USA , 3Department of Psychology, Royal Holloway, University of London, Egham Hill, Surrey TW20 0EX, UK , 4Joint senior authors
Developmental language disorder (DLD) is a neurodevelopmental condition characterised by persistent difficulties in learning and processing language. Children with DLD perform poorly on tests of nonword repetition, a crucial skill for word learning and fluent speech. Despite it being a well-documented behavioural marker for DLD, the underlying neural correlates of nonword learning in children with DLD are not well understood. As part of the Oxford Brain Organisation in Language Development project, we used functional MRI to investigate repetition-suppression effects accompanying pseudoword learning in 55 children with DLD (mean age = 12.36 years) compared with 77 typically developing age-matched controls (TD; mean age = 12.52 years). Our DLD criteria were non-verbal intelligence above 70 and performance of one SD below the normative mean on two or more of five standardized language assessments. In an event-related design, children heard and overtly repeated 2- or 4-syllable pseudowords, corresponding to “names” of aliens they viewed while being scanned. Pseudowords were presented either once or four times. After the scan, children overtly repeated each of the previously presented pseudowords. We predicted that compared with typically developing children, those with DLD would show reduced repetition-suppression effects across the four repetition trials. Data were excluded from 11 DLD and 7 TD participants who moved excessively during the functional run. Behaviourally, post-scan testing revealed that the DLD group performed more poorly on the nonword repetition task compared with their typically developing peers. Functionally, both groups activated an extensive set of brain regions bilaterally when listening to and overtly repeating the pseudowords. These included the posterior inferior frontal cortex, lateral premotor cortex, sensorimotor cortex, supplementary motor area, superior temporal cortex, and large portions of occipital and inferior temporal cortex. There was also activity in the dorsal striatum, medial temporal lobe, and cerebellum. Statistically, the groups differed in superior and inferior portions of the parietal cortex just posterior to the sensorimotor cortex activity seen in each group separately; that is, there were group differences in areas that were task negative. Significant linear decreases in task-evoked activity due to repeated exposure to and repetition of the pseudowords were seen in the TD group in the left inferior frontal cortex, anterior insular, superior temporal and occipital cortex bilaterally, medially in the supplementary motor area, anterior cingulate, and subcortically in the left dorsal striatum. The DLD group showed linear decreases limited to the superior temporal and occipital cortex bilaterally. However, statistical comparison of the two groups failed to show significant differences, perhaps due to greater variance in the DLD group in whom the learning-related decreases in activity were less robust and extensive than those seen in the TD group. In summary, during nonword repetition, children with DLD showed less task-negative activity in parietal areas relative to the TD group. Similar learning related decreases were seen in both groups despite better nonword repetition performance in the TD group. Future longitudinal investigations could shed light on the developmental trajectory of the functional neural architecture of this crucial skill.
Topic Areas: Disorders: Developmental, Language Development/Acquisition