Relating Neural Response Consistency to Complex Speech Sounds and Concurrent Language Ability in School Age Children

Background: Investigations into the neurological basis of atypical language development in autism spectrum disorders (ASD) have largely focused on cortical indices. Atypical language-relevant neural networks, however, may also arise from unreliable sensory representations. Auditory brainstem responses (ABR), auditory evoked potentials that reflect neural activity in the auditory nerve and brainstem, have been linked to reading ability in the general population and in dyslexia (Banai et al.,2009). In addition, abnormal neural conduction time, as revealed by prolonged ABR latencies, has been found in the ASD central auditory system. ABR responses recorded in childhood have recently been linked to more advanced language development displayed several years earlier, in late toddlerhood.

Objectives: The purpose of the current study is to investigate the extent to which instabilities in early stages of central auditory processing can account for differences in language development in ASD by examining the relationship between neural response consistency to complex speech sounds and current language ability.

Methods: Typically developing (TD) children (N=8, MA=11.25 years (1.9), 2 girls) and children with ASD (N=8, MA=12.5 years (3.59), 1 girl) participated. All testing was performed in the children’s homes using a portable EEG system, including a screening for normal hearing thresholds, and ABR recordings to a “da” stimulus (10.9/sec, 6000 trials) presented at 80 dB SPL. Consistency was determined by correlating the first 3000 responses with the last 3000 responses. Current language ability was measured using four subtests of the Clinical Evaluation of Language Fundamentals 5 (CELF-5); Word Classes, Formulated Sentences, Repeated Sentences, and Following Directions. Nonverbal cognition was measured using the Differential Ability Scales (DAS).

Results: No significant group differences were found for ABR consistency. The TD group scored significantly higher than the ASD group on all four CELF 5 subtest standard scores (Fs > 12.67, ps < .003) raw scores (Fs > 5.23, ps < 0.038) and age equivalents (Fs > 5.79, ps < 0.03). These group differences held (ps < 0.006, ps < 0.04, ps < 0.049) when digit span from the DAS was entered as a covariate. Significant correlations were found for ABR response consistency and three CELF-5 subtest standard scores (Word Classes, Formulated Sentences, and Repeated Sentences), for the ASD group only (rs > 0.797, ps < 0.018). Formulated Sentences raw scores and age equivalents also correlated significantly with ABR responses (rs > 0.757, ps < 0.03).

Conclusions:

In children with ASD, /da/ ABR consistency has a significant relationship to concurrent language, such that greater neural fidelity in representing auditory input is associated with more advanced language abilities. Both knowledge of how words relate to each other as well as the ability to remember and formulate grammatically correct sentences are positively correlated with how consistently sensory input was being processed early in the auditory pathway, suggesting that some origins of language delays and impairments in ASD may lie in inconsistent auditory processing. The absence of similar relationships in the TD group could be an artifact of the limited variability of both language measures and ABR responses in this group.