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Normal infant and adult auditory brainstem responses to bone-conducted tones
1Department of Otolaryngology, Rose F. Kennedy Center for Research in Mental Retardation and Human Development, Albert Einstein College of Medicine, Bronx, N.Y. 10461.
Insights
Infants show lower auditory brainstem response (ABR) thresholds for low-frequency bone-conducted tones compared to high-frequency tones. This suggests differences in auditory processing and effective intensity in infants versus adults.
Area of Science:
- Audiology
- Neuroscience
- Pediatric Medicine
Background:
- Auditory brainstem responses (ABRs) are crucial for assessing auditory pathway function.
- Bone-conducted (BC) tones bypass the outer and middle ear, directly stimulating the cochlea.
- Understanding infant auditory development is vital for early intervention.
Purpose of the Study:
- To compare ABRs to BC tones in normal-hearing infants and adults.
- To investigate age-related differences in auditory thresholds and wave V latencies.
- To explore potential differences in effective sound intensity perception between infants and adults.
Main Methods:
- Recording ABRs to 500-Hz and 2000-Hz BC tones in infants and adults.
- Analyzing auditory thresholds and wave V latencies.
- Comparing ipsilateral and contralateral wave V amplitude asymmetry.
Main Results:
- Infant ABR thresholds were lower for 500-Hz BC tones than 2000-Hz BC tones.
- Infant wave V latencies were shorter for 500-Hz BC tones compared to adults.
- Effective BC tone intensity may be higher in infants (9-17 dB).
- Significant ipsilateral-contralateral wave V asymmetry observed in infants, less so in adults.
Conclusions:
- Infants exhibit distinct auditory processing characteristics compared to adults, particularly for lower frequencies.
- Differences in wave V latency and amplitude asymmetry suggest maturational changes in the auditory brainstem.
- Findings highlight the importance of age-specific normative data for BC ABR testing in infants.
Abstract:
Auditory brainstem responses (ABRs) were recorded to 500- and 2000-Hz bone-conducted (BC) tones from normal infants and adults. Infant ABR thresholds for the 500-Hz BC tones are significantly lower than their thresholds to 2000-Hz BC tones. Infant wave V latencies to 500-Hz BC tones are significantly shorter than those of adults, whereas infant and adult responses to 2000-Hz BC tones are similar in latency, suggesting that the effective intensity of the BC tones may be 9-17 dB greater for infants than for adults. A marked asymmetry between the ipsilaterally and contralaterally recorded wave V is seen for infant responses to 500- and 2000-Hz tones at all intensities; this asymmetry is not as evident in adults, except near threshold.