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Functional anatomy of the masking level difference, an fMRI study

Wack, DS and Cox, JL and Schirda, CV and Magnano, CR and Sussman, JE and Henderson, D and Burkard, RF (2012) Functional anatomy of the masking level difference, an fMRI study. PLoS ONE, 7 (7).

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Introduction: Masking level differences (MLDs) are differences in the hearing threshold for the detection of a signal presented in a noise background, where either the phase of the signal or noise is reversed between ears. We use N0/Nπ to denote noise presented in-phase/out-of-phase between ears and S0/Sπ to denote a 500 Hz sine wave signal as in/out-of-phase. Signal detection level for the noise/signal combinations N0Sπ and NπS0 is typically 10-20 dB better than for N0S0. All combinations have the same spectrum, level, and duration of both the signal and the noise. Methods: Ten participants (5 female), age: 22-43, with N0Sπ-N0S0 MLDs greater than 10 dB, were imaged using a sparse BOLD fMRI sequence, with a 9 second gap (1 second quiet preceding stimuli). Band-pass (400-600 Hz) noise and an enveloped signal (.25 second tone burst, 50% duty-cycle) were used to create the stimuli. Brain maps of statistically significant regions were formed from a second-level analysis using SPM5. Results: The contrast NπS0- N0Sπ had significant regions of activation in the right pulvinar, corpus callosum, and insula bilaterally. The left inferior frontal gyrus had significant activation for contrasts N0Sπ-N0S0 and NπS0-N0S0. The contrast N0S0-N0Sπ revealed a region in the right insula, and the contrast N0S0-NπS0 had a region of significance in the left insula. Conclusion: Our results extend the view that the thalamus acts as a gating mechanism to enable dichotic listening, and suggest that MLD processing is accomplished through thalamic communication with the insula, which communicate across the corpus callosum to either enhance or diminish the binaural signal (depending on the MLD condition). The audibility improvement of the signal with both MLD conditions is likely reflected by activation in the left inferior frontal gyrus, a late stage in the what/where model of auditory processing. © 2012 Wack et al.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Wack, DS
Cox, JL
Schirda, CVclaudiu.schirda@pitt.eduCVSST5
Magnano, CR
Sussman, JE
Henderson, D
Burkard, RF
ContributionContributors NameEmailPitt UsernameORCID
Date: 27 July 2012
Date Type: Publication
Journal or Publication Title: PLoS ONE
Volume: 7
Number: 7
DOI or Unique Handle: 10.1371/journal.pone.0041263
Schools and Programs: School of Medicine > Radiology
Refereed: Yes
Other ID: NLM PMC3407245
PubMed Central ID: PMC3407245
PubMed ID: 22848453
Date Deposited: 10 Oct 2012 13:54
Last Modified: 02 Feb 2019 16:58


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