Auditory brainstem responses in adults with autism spectrum disorder.

OBJECTIVE: To investigate possible differences in the auditory peripheral and brainstem functions between adults with autism spectrum disorder (ASD) and neurotypical (NT) adults. METHODS: Click-evoked auditory brainstem responses (ABRs) were obtained from 17 high-functioning ASD adults (aged 21-38 years) and 20 NT adults (aged 22-36 years). A relatively large number of stimulus presentations (6000) were adopted, and ABRs by horizontal and vertical electrode montages were evaluated, in order to allow precise evaluations of early ABR components. RESULTS: Waves I, II, III, and V were identified in the vertical electrode montage, and wave I and the summating potential (SP) in electrocochleograms were identified in the horizontal electrode montage. There were no significant group differences in the wave I, II, III, and V latencies or the interpeak latencies (IPLs) in the vertical electrode montage. In the horizontal montage, the ASD adults exhibited significantly shortened SP latencies compared with the NT adults, whereas there was no significant group difference in the wave I latency. CONCLUSION: The ASD adults may have the abnormalities of processing more in the peripheral auditory system than in the brainstem. SIGNIFICANCE: The current study suggests that the peripheral abnormality is associated with ASD.

Elderly listeners with low intelligibility scores under reverberation show degraded subcortical representation of reverberant speech.

In order to elucidate why many elderly listeners have difficulty understanding speech under reverberation, we investigated the relationship between word intelligibility and auditory brainstem responses (ABRs) in 28 elderly listeners. We hypothesized that the elderly listeners with low word intelligibility scores under reverberation would show degraded subcortical encoding information of reverberant speech as expressed in their ABRs towards a reverberant /da/ syllable. The participants were divided into two groups (top and bottom performance groups) according to their word intelligibility scores for anechoic and reverberant words, and ABR characteristics between groups were compared. We found that correlation coefficients between responses to anechoic and reverberant /da/ were lower in the bottom performance group than in the top performance group. This result suggests that degraded neural representation toward information of reverberant speech may account for lower intelligibility of reverberant speech in elderly listeners.

Correlations between word intelligibility under reverberation and speech auditory brainstem responses in elderly listeners.

OBJECTIVE: To investigate the relationship between speech auditory brainstem responses (speech ABRs) and word intelligibility under reverberation in elderly adults. METHODS: Word intelligibility for words under four reverberation times (RTs) of 0, 0.5, 1.0, 1.5s, and speech ABRs to the speech syllable/da/ were obtained from 30 elderly listeners. Root mean square (RMS) amplitudes and discrete Fourier transform (DFT) amplitudes were calculated for ADD and SUB responses in the speech ABRs. RESULTS: No significant correlations were found between the word intelligibility scores under reverberation and the ADD response components. However, in the SUB responses we found that the DFT amplitudes associated with H4-SUB, H5-SUB, H8-SUB, H9-SUB and H10-SUB significantly correlated with the word intelligibility scores for words under reverberation. With Bonferroni correction, the DFT amplitudes for H5-SUB and the intelligibility scores for words with the RT of 0.5s and 1.5s were significant. CONCLUSIONS: Word intelligibility under reverberation in elderly listeners is related to their ability to encode the temporal fine structure of speech. SIGNIFICANCE: The results expand knowledge about subcortical responses of elderly listeners in daily-life listening situations. The SUB responses of speech ABR could be useful as an objective indicator to predict word intelligibility under reverberation.