Otoacoustic Emissions and Auditory Feedback in Minimally Verbal Children with ASD

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Principal Investigators: Loisa Bennetto, PhD, Anne Luebke, PhD

Auditory processing deficits have been found to be one of the earliest signs of an autism spectrum disorder (ASD). Testing early auditory processing is difficult in very young, minimally verbal children, but the integrity of outer hair cell function can be evaluated reliably using otoacoustic emissions (OAEs). Sound causes contractions of the outer hair cells and generates acoustic signals (OAEs), which can be recorded in the external ear canal (Kemp, 2002). Measuring these signals is noninvasive and reliable, and is a routine approach to testing auditory functioning in children as young as infancy.

Our previous research has shown that high functioning children and adolescents with ASD (with normal hearing thresholds) have reduced OAEs using multiple tests in the 1 kHz frequency region critical for speech, yet the other frequencies tested between 0.5-8 kHz were unaffected (Bennetto, Keith, Allen, & Luebke, 2017). Moreover, we found that lower OAEs in this 1 kHz region were significantly related to greater autism severity in the ASD group.

In this study, we are investigating how these previous findings translate to younger children with ASD by using non-invasive measures of cochlear function that do not require behavioral responses. Our overall hypothesis is that physiological measures of cochlear function and cochlear efferent feedback strength will be significantly reduced in minimally verbal children with ASD in the 1 kHz frequency region critical for speech processing. The specific aims of the project will use miniature speaker-microphone earplugs, to measure baseline acoustic signals (otoacoustic emissions) generated by sensory cells in the inner ear, and also test if these emissions are suppressed in the presence of background noise.

This research will advance our understanding of how both verbal and minimally verbal young children with autism (4-6 yrs) can hear certain sounds important for speech recognition and eventually could be used as an objective early indicator of auditory processing differences in autism.

This project is funded by NICHD [1R21DC016165-01].

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