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Cortical Representation of Frequency Changes in Cochlear Implant Users

Liang, Chun, Ph.D.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504796317530661

Abstract Details

2017, PhD, University of Cincinnati, Allied Health Sciences: Communication Sciences and Disorders.
Objective: The acoustic change complex (ACC) is a type of cortical auditory evoked potentials (CAEP) elicited by an acoustic change in an ongoing stimulus. The purpose of this study were: 1) to characterize waveform features and brain activation patterns of the ACC evoked by frequency changes, and 2) to determine if the ACC can serve as an objective tool to predict frequency change detection threshold (FCDT) measured behaviorally in cochlear implant (CI) users. Methods: Twelve post-lingually deafened adult CI users and 12 normal-hearing (NH) young listeners participated in this study. A psychoacoustic test and electroencephalography (EEG) recordings were administered in each participant. For the psychoacoustic test, the stimuli were a series of 160 Hz base frequency tones containing different magnitudes of upward frequency changes. The FCDTs were measured. For EEG recordings, the stimuli were similar to those in the psychoacoustic test. The base frequencies were 160 Hz or 1200 Hz. The magnitudes of frequency changes were 0% (no change), 5%, and 50% change at each base frequency. The onset CAEP (N1-P2 complex) evoked by stimulus onset and the ACC (N1’-P2’ complex) evoked by frequency changes were analyzed. A source localization analysis with standardized low-resolution brain electromagnetic tomography (sLORETA) was further used to localize brain regions that were associated with the onset CAEP N1 and the ACC N1’. The correlation between the ACC measures (wave peak amplitude, latency, and current source density) and the FCDT was examined. Results: The ACC and onset CAEP peaks displayed longer latencies in CI users than in NH listeners (p<0.05), with this trend more prominent for the ACC peaks. The N1’P2 amplitude of the ACC was significantly smaller in CI users than in NH listeners (p<0.05). With the 160 Hz base frequency, the N1’ latency evoked by 50% frequency change was significantly correlated with the FCDT in CI group (r=0.48, p<0.05). The current source density responding to the ACC N1’ in CI users showed different brain activation patterns compared to that in NH listeners. sLORETA statistical images derived from the comparison between the ACC N1’ and the onset CAEP N1 showed differences between NH listeners and CI users: the NH group showed a significant activation in inferior parietal lobe, precentral lobe, and cingulate gyrus, while the CI group did not show a significant activation. The right CI ears with good performance (lower FCDT) have a larger superior temporal gyrus/inferior frontal gyrus (STG/IFG) ratio on the contralateral side, or a stronger activation in the left STG and weaker activation in the left IFG. This trend was not found in left CI ears. Conclusion: The ACC could serve as a valuable objective tool in assessing frequency change detection capability for CI users. The ACC N1’ and the onset CAEP N1 have different neural mechanisms, with the former involving more recruitment of neural resources related to auditory discrimination that triggers auditory attention. sLORETA provides a neuroimaging tool in revealing the brain activation patterns in CI users who cannot be tested with other neuroimaging tools.
Fawen Zhang, Ph.D. (Committee Chair)
Pamara Chang (Committee Member)
Brian Earl (Committee Member)
Noah Silbert, Ph.D. (Committee Member)
100 p.
Health Sciences
Cochlear Implant; Acoustic change complex; sLORETA; Frequency change detection

Recommended Citations

Citations

  • Liang, C. (2017). Cortical Representation of Frequency Changes in Cochlear Implant Users [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504796317530661

    APA Style (7th edition)

  • Liang, Chun. Cortical Representation of Frequency Changes in Cochlear Implant Users. 2017. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504796317530661.

    MLA Style (8th edition)

  • Liang, Chun. "Cortical Representation of Frequency Changes in Cochlear Implant Users." Doctoral dissertation, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504796317530661

    Chicago Manual of Style (17th edition)

ucin1504796317530661
327
© 2017, some rights reserved.Creative Commons License Cortical Representation of Frequency Changes in Cochlear Implant Users by Chun Liang Ph.D. is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.