Auditory Brainstem Responses at 8 kHz: Data From Normal-Hearing Infants and Adults.

Purpose: The goal of this study is to examine auditory brainstem responses (ABRs) recorded for click and 8-kHz tone bursts (TBs) from normal-hearing infants and adults using a clinical auditory-evoked potential system. Method: Infants (n = 34) and adults (n = 10) with normal hearing participated in this study. ABRs for click stimuli and 8-kHz TBs were recorded at 70 dB nHL. ABR thresholds for 8-kHz TBs were obtained from both groups. In addition, behavioral thresholds for the 8-kHz TB stimulus were obtained from adults. Given that adults can participate in traditional behavioral testing, their data were included to demonstrate a correlation between behavioral thresholds for 8-kHz TB and electrophysiological thresholds for the same stimulus. Results: Peak I latency of the ABR for both click and 8-kHz TBs at 70 dB nHL were similar between adults and infants. Latencies of Peaks III and V of the ABR for both click and 8-kHz TBs were significantly prolonged in infants when compared to adults. Infants' ABR thresholds for 8 kHz were significantly elevated when compared to adults. Conclusion: The ABR for 8-kHz TB stimuli is not adultlike in newborn infants and this could be due to immature synaptic and axonal processing.