By Matthew Barbara, Communication Sciences and Disorders; Alison Reynolds, Communication Sciences and Disorders; Kelli McGuire, University of Cincinnati; Gabrielle Firestone, University of Cincinnati; Kristen Dairymple, University of Cincinnati; Quian-Jie Fu, University of California, Los Angeles
Advisor: Fawen Zhang
Abstract: This study aimed to examine cortical auditory evoked potentials (CAEPs) compared to changes in frequency (F), location (L), or both (F+L) by means of the acoustic change complex (ACC). When elicited, the ACC indicates that the brain has detected changes within a sound. Participants consisted of fifteen normal-hearing adults, ranging in age from 20-30 years old. During the study, pure tone stimuli were presented in 1-second intervals with a perceivable change in the middle of the tone. In total, there were 6 changes in the stimuli, each presented to the listener 400 times. Electroencephalographic (EEG) measurements of each participant were recorded and analyzed. The recorded CAEPs of each stimulus is henceforth referred to as change-CAEPÕs.
The smallest change-CAEPÕs resulted from the 5% F-change stimulus and the largest resulted from the L+50% F-change. These findings suggest that change-CAEP waveform amplitude is related to the physical magnitude of the change. Additionally, there were differing processing patterns for L-change vs. F-change, suggesting different cortical processing mechanisms for the ÒwhereÓ and ÒwhatÓ information of sound. This finding indicates that there is a common mechanism for sound localization and discrimination. Lastly, large changes evoke a stronger activation in the postcentral gyrus and cingulate gyrus, suggesting the involvement of auditory working memory. The data collected will be used to formulate a baseline to identify the magnitude of malformation in patients with abnormal conditions.