Objectives: To determine whether the auditory brainstem responses to speech syllables in children with ASD differ in comparison with typically developing (TD) controls.
Methods: Speech stimuli, including a consonant-vowel speech syllable /da/ and two fully voiced /ya/ syllables, with ascending and descending pitch contours, were delivered monaurally to the right ear to children (7-13 years) with ASD (N=21) and age- and IQ-matched TD children (N=18). All subjects had normal hearing by air threshold audiometry (20 dB HL) and click-evoked wave V latency and normal mental ability.
Results: /da/-evoked potentials showed altered representation of stimulus timing and frequency, reduced fidelity to stimulus, and greater degradation by noise in ASD vs. TD (p < 0.05). A subset of the ASD group (N=5) also showed reduced phase locking and pitch tracking in response to /ya/ (p < 0.02). A limited number (3/6) of ASD subjects who underwent auditory training demonstrated improved brainstem transcription of speech, whereas ASD subjects without training (N=6) had stable responses over time.
Conclusions: These data provide unique evidence of deficient brainstem processing of speech sounds in ASD, and suggest a relationship between aberrant prosody and impaired subcortical pitch tracking. Because the speech-evoked auditory brainstem response is both passively-elicited and malleable, it may have clinical utility in detection of ASD as well as monitoring responses to intervention.