Maturational Differences in Auditory Event-Related Potentials According to Presence Versus Absence of Language Impairment in Children with Autism Spectrum Disorder

Background:  Age-related maturation in sound processing has previously been examined in children by evaluating auditory event-related potentials (AEPs) in response to a single tone using intra-class correlation (ICC).  Using this approach, it has been shown that children who have a language impairment but are otherwise typically developing (specific language impairment) have immature AEPs that resemble younger children with typical development. This suggests that maturational delay in auditory cortical processing may contribute to language impairment. Less is known about language impairment in autism spectrum disorder (ASD).  Many children with ASD have an oral language impairment, and some have argued that the etiology of language impairment in ASD overlaps with specific language impairment. Few studies have focused on auditory processing in children with ASD, and no study to date has explored the use of ICC to evaluate auditory cortical maturation in children with ASD who have impaired language (ASD-LI) or normal language (ASD-LN).

Objectives:  1) To evaluate the maturation of AEP waveforms of children with ASD-LN and ASD-LI compared to normative waveforms of children with typical development; 2) to compare AEP maturational differences between ASD-LN and ASD-LI.

Methods:  Eighty-four children aged 7-11 years (typical development: N=67, ASD-LI: N=7, ASD-LN: N=10) participated in a passive AEP paradigm where 225 trials of a 50ms, 490Hz tone were presented binaurally. A 128-channel EGI system recorded AEPs during stimulus presentation while the child watched a silent movie. Children in the groups with typical development and ASD-LN had standard scores ≥ 85 on the CELF–4, while those with ASD-LI scored < 85 (greater than 1 SD below the mean). Children with typical development were separated into four groups according to age, and a normative grand averaged AEP waveform was generated for each age: 7, 8, 9, 10 years (N=15, 16, 22, 14, respectively). The individual waveforms of each child with ASD-LI and ASD-LN were compared to each of these four normative waveforms at three frontal electrodes (F3, Fz, F4) and an ICC was calculated for each comparison. Since higher ICCs indicate a better resemblance of two waveforms, each electrode was assigned an age-equivalent based on the comparison that yielded the highest ICC. The average age-equivalents of the three frontal electrodes between the groups with ASD-LI and ASD-LN were compared using independent t-tests.

Results:  Children with ASD-LI and ASD-LN did not significantly differ in chronological age (mean age = 9.1 and 9.0 years, respectively), but did significantly differ in language ability (mean standard score = 70 and 99). In terms of AEP maturity, the ICC-estimated age-equivalents of the waveforms of children with ALI were significantly lower than for those with ASD-LN (mean age-equivalent = 7.4 years and 8.4 years, respectively, t(15)=2.71 p<.05).

Conclusions:  Results revealed that AEP waveforms in children with ASD-LI were less mature than those with ASD-LN. Such immaturity was not related to chronological age, but rather to language ability. This suggests that, as previously reported for specific language impairment, language impairment in ASD may be related to delayed neural maturation of auditory processing.