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Poster E10, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall

Neural Stability and Language in Autism Spectrum Disorder

Lisa Tecoulesco1, Erika Skoe1, Letitia R Naigles1;1University of Connecticut

Auditory brainstem responses (ABRs) are auditory evoked potentials reflecting neural activity in the auditory nerve and brainstem. Previous studies associated low ABR stability with poor reading ability, suggesting stability (i.e. the extent to which the same signal produces the same neural response) might be predictive of language ability. Variability in language performance is a well-known characteristic of Autism Spectrum Disorder (ASD), and recent work also reports low ABR stability in this population. Work from our lab, however, revealed no group-level differences in ABR stability between typically-developing (TD) children and children with ASD, but found that at the level of individual differences, stability was correlated with phonology and syntactic ability. This suggests ABR stability is an index of language ability but not of ASD. The literature linking ABR stability and language ability has focused on the repeatability of speech-evoked ABRs by analyzing the frequency-following response (FFR) component of the ABR in the time domain. FFRs can also be analyzed in the frequency domain, revealing the fidelity with which specific speech frequencies, such as the fundamental frequency (F0), are faithfully encoded by the auditory system. The F0 imparts information about affective intent and speaker identity, two areas of documented differences in ASD. Building off evidence that neural tracking of the F0 contour of a speech stimulus is less faithful in children with ASD, the current study asks whether the stability of this spectral encoding is predictive of language ability in children with ASD. Twenty-four children participated in the study, twelve TD (M=11.25 years) and twelve with ASD (M=12.5 years), all with normal hearing thresholds. Speech-ABRs were recorded to a “da” (40ms) stimulus presented at 80 dB SPL and a rate of 10.9 per second. Two ABR sub-averages (3000 trials each) were computed and the FFR component of each sub-average was converted to the frequency domain via Fourier analysis. From the FFR, two measures of F0 encoding were derived: the average FFR amplitude over the F0 range (75-175Hz); and the stability of spectral encoding, calculated as the absolute difference in amplitude between the two sub-averages (smaller values indicative of more response stability). Language ability was measured using two subtests of the Clinical Evaluation of Language Fundamentals (CELF-5), and phonology was assessed using a novel word discrimination task. No group differences were found for the amplitude or neural stability of F0 encoding. However, different relationships to language were observed for each group. In the ASD group, Spearman’s rank correlations revealed greater F0 stability related to better phonological discrimination (rs=-.705,p=.01), semantics (rs=-.729,p=.007), and syntax (rs=-.718,p=.009). By contrast, F0 stability did not relate to any language measure for the TD group. This suggests that for children with ASD, language acquisition may be dependent on the stability with which the subcortical auditory system represents particular stimulus features, especially speech frequencies that carry information about who is speaking and affective intent. Future work will attempt to replicate this finding, while expanding the stimuli (to include multiple speakers and multiple syllables) to dissociate F0 effects of speaker vs. affect.

Themes: Disorders: Developmental, Perception: Auditory
Method: Electrophysiology (MEG/EEG/ECOG)

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