Bigger Is Better: Increasing Cortical Auditory Response Amplitude Via Stimulus Spectral Complexity.

Abstract

To determine the influence of auditory stimuli spectral characteristics on cortical auditory evoked potentials (CAEPs). CAEPs were obtained from 15 normal-hearing adults in response to six multitone (MT), four pure-tone (PT), and two narrowband noise stimuli. The sounds were presented at 10, 20, and 40 dB above threshold, which were estimated behaviorally beforehand. The root mean square amplitude of the CAEP and the detectability of the response were calculated and analyzed. Amplitudes of the CAEPs to the MT were significantly larger compared with PT for stimuli with frequencies centered around 1, 2, and 4 kHz, whereas no significant difference was found for 0.5 kHz. The objective detection score for the MT was significantly higher compared with the PT. For the 1- and 2-kHz stimuli, the CAEP amplitudes to narrowband noise were not significantly different than those evoked by PT. The study supports the notion that spectral complexity, not just bandwidth, has an impact on the CAEP amplitude for stimuli with center frequency above 0.5 kHz. The implication of these findings is that the clinical test time required to estimate thresholds can potentially be decreased by using complex band-limited MT rather than conventional PT stimuli.