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Poster C37, Thursday, November 9, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Individual differences in the cortical activity dynamics of auditory word processing in adolescents with SLI using anatomically constrained magnetoencephalography (aMEG)

Nicholas Walker1, Julia L. Evans1,2, Timothy T. Brown2, Amy Berglund1, Meredith Scheppele1, Andrea W. Fung1;1University of Texas at Dallas, 2UCSD

Behavioral and neurobiological evidence indicates that children with Specific Language Impairment (SLI) have atypical spoken word recognition. Behavioral studies show that children with SLI require more of the perceptual input to activate a lexical candidate and experience greater lexical decay as compared to typical children during real-time spoken word recognition (Mainela-Arnold, Evans, Coady, 2008; McMurray, Samelson, Lee & Tomblin, 2010). Magneto- and electro- encephalography (M/EEG) studies also show atypical N400-like event-related activity in children with Specific Language Impairments as compared to normal controls (Helenius, et al., 2014; Brown, et al. 2014). However, EEG signals cannot be precisely localized to their cerebral sources because of inherent biophysical limitations; electric potentials are smeared, distorted, and deflected as they pass through different tissue types (e.g., brain, dura, skull, scalp). MEG, in contrast, allows good localization precision but still depends on assumptions made about the complexity of the sources. This study examines event-related magnetic fields for spoken word recognition in adolescents with SLI and normal language using anatomically constrained magnetoencephalography (aMEG) and individual differences anaylses. aMEG integrates millisecond-wise neurophysiological data with individual cortical surface anatomy, providing noise-normalized, dynamic statistical parametric maps (dSPMs) of brain activity for each subject. Using high-density aMEG (Brown, et al., 2014), activity time courses were examined in the primary auditory cortex for a passive lexical processing task in three adolescents with SLI, seven age-matched typical developing controls (TD), and eight adults. Using functionally defined ROI’s, we measured the amplitudes and peak latencies of cortical activity focusing on primary auditory areas bilaterally. Responses to novel, fast-repeated (1 sec), and slow-repeated (10 min) words were compared. Most notably, the SLI group showed lack of any high-amplitude early sensory response (~90 ms) within the left hemisphere (LH) for either novel or repeated words, in marked contrast to both the TD and adult groups. In addition, at 200 ms, SLI subjects showed no significant LH word repetition effect, which was comparable to TD children but in contrast with adults who showed significant repetition suppression. During lexical semantic latencies (~300-500 ms), the SLI group differed significantly from both TD and adult subjects by showing greater LH responses to novel words. Finally, within the right hemisphere (RH), the SLI group showed a repetition suppression effect at 70 ms, which was absent in both adult and TD children. Altogether, our results suggest there exist large differences in cortical responses between individuals with SLI and control subjects that begin at the very earliest stages of sensory auditory function. Using passive auditory word presentation, these effects represent a collection of potential aMEG biomarkers for SLI that differentiate them from both TD children and adults.

Topic Area: Language Disorders

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