Auditory Integration As a Neural Marker of Language Disorders in ASD

Background:  Many children with Autism Spectrum Disorder (ASD) have oral language impairments, but the neural basis of these language problems is not well understood. Here, we considered one candidate marker of language impairment: the ability of the auditory system to integrate information over time. Auditory perception is the outcome of a neural process that integrates acoustic elements over a brief time frame, termed the auditory window of integration (AWI). The smaller the AWI, the better the resolution of the signal. Research has suggested that, like language, the AWI becomes refined (smaller) as children age, and that individuals with impaired language may have an immature (larger) AWI. The relation between AWI and language ability in children with ASD has received limited attention to date.

Objectives:  We compared the length of the AWI in children with autism spectrum and/or language disorders to that of their typical peers, in order to explore whether delayed maturation of cortical auditory integration may be associated with language impairment, ASD, or both.

Methods:  Participants were 50 children aged 7-10 years in four groups: ASD without language impairment (ALN), ASD with language impairment (ALI), language impairment without ASD (Specific Language Impairment - SLI) and typical development (TD). We used a passive event-related potential (ERP) paradigm to examine the length of the AWI in individual children. A 128-channel EGI system recorded ERPs during binaural stimulus presentation while the child watched a silent movie. Five trails of 225 stimuli each were presented: a single 50ms tone and four tone pairs, each consisting of two 50ms tones separated by one of four gaps (100, 200, 300, and 400ms). The presence or absence of the P1/N2 complex (the neural correlate of distinct tone identification) to the second tone in each child was determined by comparison to the child’s waveform generated in response to a single tone, for all four conditions.

Results:  The majority of children across all four groups demonstrated neural responses to both tones in the 300 and 400ms gap conditions, and most children failed to demonstrate a second tone response in the 100ms condition. However, the groups differed in the 200ms gap condition. At this presentation rate, significantly fewer children with SLI and ALI (roughly 30% of children in each group) had second tone responses than children with ALN and TD (more than 60% of children in each group), χ²(3, N=50)=9.0, p=.029.

Conclusions:  Results estimated the AWI to fall between 200-300ms in children with SLI and ALI, a less mature, lower resolution than that estimated for children with ALN and TD (which was between 100-200ms). These findings suggest that maturational delays in how the brain processes basic auditory stimuli may contribute to the impairments in understanding and using language found in children with language disorders, both within and outside the context of ASD. In future investigations, this paradigm would be particularly well-suited to explore with much younger and more disabled children, because it is quick, non-invasive, and does not require active judgment or participation.