Steady-State Analysis of Auditory Evoked Potentials over a Wide Range of Stimulus Repetition Rates: Profile in Children versus Adults

摘要

This study profiled auditory steady-state response amplitudes in children (i.e., six to nine years of age) and in adults (i.e., 18 to 35 years of age) over a wide range of repetition rates, specifically a range well embracing component waves of conventionally stimulated and recorded transient auditory evoked responses. Response amplitudes were measured at repetition rates from 0.75 to 80 Hz. Repetition rates of 10 Hz or less have received little attention in the context of the ASSR approach which is speculated to provide technical advantages, if not additional information, to the more traditional transient protocols, at least for some applications as follows: (1) to permit characterization of subject age-dependent amplitudes; (2) to allow an exploratory examination of the effects of repetition rate on response amplitude during natural sleep, to demonstrate if results differed from those obtained when subjects were awake, and (3) to explore the use of both the fundamental and harmonics in the characterization of the response amplitude versus the typical measure of amplitude in transient analysis. Planned comparisons were conducted to evaluate the amplitude differences observed between the age groups (i.e., children and adults) and between arousal conditions (i.e., adults awake and adults asleep) across modulation frequencies. The results of this study show that the amplitude was largest at the two lowest modulation frequencies for both adults and children. Furthermore, response amplitudes for children were significantly higher than those for adults at all modulation frequencies up to 5 Hz. Response amplitudes for adults during sleep also were significantly higher than those responses of adults while awake at 0.75 and 1.25 Hz. Good reliability overall was observed for these response measures in both adults and children. An amplitude measure defined as the harmonic sum yielded results paralleling the profile of response amplitudes as a function of repetition rate that may be extracted from the literature, although with some differences, the significance of which remains to be determined. Of pragmatic importance is that this profile could be determined without subjective wave identification and/or interpretation and thus by a method that is inherently more objective than conventional, transient AEP tests.