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Updated: May 17, 2026
Infant Auditory Processing and Event-related Brain Oscillations
Published on: July 1, 2015
Auditory brainstem responses to broad-band chirps: amplitude growth functions in sedated and anaesthetised infants
Roland Mühler1, Torsten Rahne, Jesko L Verhey
1Department of Experimental Audiology, Otto von Guericke University, Magdeburg, Germany. muehler@med.ovgu.de
Insights
Broadband chirp stimuli evoke larger auditory brainstem response (ABR) amplitudes in infants compared to click stimuli. This finding in pediatric audiology suggests reduced recording times for objective hearing threshold estimation in young children.
Area of Science:
- Audiology
- Neuroscience
- Pediatrics
Background:
- Optimized broadband chirp stimuli have been proposed for objective hearing threshold estimation using auditory brainstem responses (ABRs).
- Chirp stimuli compensate for travelling wave delays, potentially evoking larger ABR amplitudes than click stimuli, particularly in adults.
Purpose of the Study:
- To analyze the amplitude of chirp-evoked ABRs in infants under 48 months of age.
- To compare these ABR amplitudes with existing literature data.
- To investigate the maturation of chirp-evoked ABRs in relation to age.
Main Methods:
- Retrospective analysis of chirp-evoked ABR recordings from 46 infants under sedation or general anesthesia.
- Measurement of Wave V amplitude as a function of stimulus intensity, adjusted to individual sensation levels (dB SL).
- Calculation of individual amplitude growth functions and separate analysis for infants below and above 18 months.
Main Results:
- Chirp-evoked ABR amplitudes were larger than click-evoked ABR amplitudes reported in the literature for young infants.
- Infants over 18 months showed ABR amplitudes comparable to normal-hearing adults.
- Significantly smaller amplitudes were observed in infants below 18 months compared to older infants; no significant difference was found between sedation and anesthesia.
Conclusions:
- Higher ABR amplitudes elicited by broadband chirp stimuli can reduce recording time in young infants.
- This method offers a more efficient approach for objective hearing assessment in pediatric populations.
Objective:
Recently an optimized broad-band chirp stimulus has been proposed for the objective estimation of hearing thresholds with auditory brainstem responses (ABRs). Several studies have demonstrated that this stimulus, compensating for the travelling wave delay of the frequency components of a click stimulus at the basilar membrane, evokes larger ABR amplitudes in adults. This study analyses the amplitude of chirp-evoked ABRs recorded in infants below 48 month of age under clinical conditions and compares these results with literature data.
Methods:
Chirp-evoked ABR recordings in 46 infants under chloral hydrate sedation or general anaesthesia were analysed retrospectively. The amplitude of the wave V was measured as a function of the stimulus intensity. To compare ABR amplitudes across infants with different hearing losses, the stimulus intensity was readjusted to the subjects' individual physiological threshold in dB SL (sensation level). Individual wave V amplitudes were plotted against stimulus intensity and individual amplitude growth functions were calculated. To investigate the maturation of chirp-evoked ABR, data from infants below and above 18 months of age were analysed separately.
Results:
Chirp-evoked ABR amplitudes in both age groups were larger than the click-evoked ABR amplitudes in young infants from the literature. Amplitudes of chirp-evoked ABR in infants above 18 months of age were not substantially smaller than those reported for normal hearing adults. Amplitudes recorded in infants below 18 months were significantly smaller than those in infants above 18 months. A significant difference between chirp-evoked ABR amplitudes recorded in sedation or under general anaesthesia was not found.
Conclusions:
The higher amplitudes of ABR elicited by a broadband chirp stimulus allow for a reduction of the recording time in young infants.
