Evaluation of Mismatch Negativity as a Biomarker for Language Impairment in Autism Spectrum Disorders

Finding an early and objective way to identify language impairment in autism spectrum disorder (ASD) has the potential to lead to earlier speech and language intervention for affected children. Previous magnetoencephalography studies utilizing the mismatch field component (MMF) component have shown that increased MMF latency is a predictor of language impairment in children with ASD. We attempted to replicate these results using the mismatch negativity (MMN), the electroencephalography (EEG) equivalent of MMF. EEG was recorded in children ages 5 to 10 with ASD plus language impairment (ASD +LI), ASD minus language impairment (ASD --LI), and typically developing controls (TD) during a passive auditory oddball experiment presenting speech and nonspeech sounds. Contrary to previous MMF findings, individuals with ASD +LI demonstrated decreased MMN latency in the left hemisphere in response to novel vowel sounds compared to individuals with ASD --LI and TD controls. A positive correlation between left hemisphere MMN latency and language scores on the Clinical Evaluation of Language Fundamentals was found when combining both ASD groups. Our results lend support to the theory that some children with ASD +LI have increased connectivity in primary sensory cortices at the expense of computational connectivity between association areas of the brain. This may account for faster speech sound processing despite low language scores in these children. Further research needs to be done in order to determine if grouping children by hyper-- versus hyposensitivity to auditory stimuli could explain conflicting results between studies and elucidate a neurophysiological biomarker of language impairment in subgroups of children with ASD.