| Age-dependent changes in auditory brainstem response (ABR) characteristics have been utilized to study the postnatal maturation of the auditory pathways from the auditory nerve to the lateral lemniscus (e.g., Salamy & McKean, 1976). The recording of an ABR, however, is dependent on the response of the auditory periphery (e.g., Sininger, Abdala, & Cone-Wesson, 1997). The effect of the conductive and sensory mechanisms on the transmission of sound from the external auditory canal to the cochlea in infants is unknown. The effect that the external and middle ears have on ABR measures from infants is unknown (e.g., Saunders, Doan, & Cohen, 1993).; This study considered the frequency dependence of ABR interpeak intervals, a level independent measure (e.g., Stockard, Stockard, Westmoreland, & Corfits, 1979). Frequency specific ABR interpeak intervals from neonates were compared to those of young adults with normal hearing. ABRs were recorded with each of two tone pips, 1000 and 8000 Hz, at each of two levels, 80 and 90 dB pSPL. ABR interpeak intervals were then compared across frequencies, levels, and age groups.; Three hypotheses were evaluated. First, it was hypothesized that for both adults and neonates interpeak intervals would be longer for 8000 Hz than for 1000 Hz. Interpeak intervals I–III, and III–V from adults were longer to 8000 Hz than to 1000 Hz. Interpeak intervals I–III, III–V, and I–V from neonates were not longer to 1000 Hz or 8000 Hz. Thus, the first hypothesis was correct for adults and incorrect for neonates. Second, it was hypothesized that ABR interpeak intervals I–III, III–V, and I–V would be longer for neonates than for adults. Each interpeak interval I–III, III–V, and I–V for each stimulus frequency was longer from neonates than from adults. Hypothesis 2, therefore, was correct. Third, it was hypothesized that the effect of frequency on interpeak intervals would be less for neonates than for adults. The interpeak intervals from adults were longer to 8000 Hz than to 1000 Hz. Interpeak intervals from neonates were not statistically different by stimulus frequency. Thus, the effect of stimulus frequency on interpeak intervals from neonates was less than for adults. |
