Electrophysiological Evidence for the Sources of the Masking Level Difference Purpose The purpose of this review article is to review evidence from auditory evoked potential studies to describe the contributions of the auditory brainstem and cortex to the generation of the masking level difference (MLD). Method A literature review was performed, focusing on the auditory brainstem, middle, and ... Review Article
Review Article  |   August 16, 2017
Electrophysiological Evidence for the Sources of the Masking Level Difference
 
Author Affiliations & Notes
  • Cynthia G. Fowler
    University of Wisconsin–Madison
  • Disclosure: The author has declared that no competing interests existed at the time of publication.
    Disclosure: The author has declared that no competing interests existed at the time of publication. ×
  • Correspondence to Cynthia Fowler: cgfowler@wisc.edu
  • Editor: Frederick Gallun
    Editor: Frederick Gallun×
  • Associate Editor: Suzanne Purdy
    Associate Editor: Suzanne Purdy×
Article Information
Hearing / Review Article
Review Article   |   August 16, 2017
Electrophysiological Evidence for the Sources of the Masking Level Difference
Journal of Speech, Language, and Hearing Research, August 2017, Vol. 60, 2364-2374. doi:10.1044/2017_JSLHR-H-16-0251
History: Received June 15, 2016 , Revised January 1, 2017 , Accepted February 6, 2017
 
Journal of Speech, Language, and Hearing Research, August 2017, Vol. 60, 2364-2374. doi:10.1044/2017_JSLHR-H-16-0251
History: Received June 15, 2016; Revised January 1, 2017; Accepted February 6, 2017

Purpose The purpose of this review article is to review evidence from auditory evoked potential studies to describe the contributions of the auditory brainstem and cortex to the generation of the masking level difference (MLD).

Method A literature review was performed, focusing on the auditory brainstem, middle, and late latency responses used in protocols similar to those used to generate the behavioral MLD.

Results Temporal coding of the signals necessary for generating the MLD occurs in the auditory periphery and brainstem. Brainstem disorders up to wave III of the auditory brainstem response (ABR) can disrupt the MLD. The full MLD requires input to the generators of the auditory late latency potentials to produce all characteristics of the MLD; these characteristics include threshold differences for various binaural signal and noise conditions. Studies using central auditory lesions are beginning to identify the cortical effects on the MLD.

Conclusions The MLD requires auditory processing from the periphery to cortical areas. A healthy auditory periphery and brainstem codes temporal synchrony, which is essential for the ABR. Threshold differences require engaging cortical function beyond the primary auditory cortex. More studies using cortical lesions and evoked potentials or imaging should clarify the specific cortical areas involved in the MLD.

Acknowledgments
Portions of this review article were presented at the 2013 Appalachian Spring Conference in Mountain Home, TN, in honor of Richard H. Wilson.
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