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fMRI Mapping of Brain Activity Associated with the Vocal Production of Consonant and Dissonant Intervals
Published on: May 23, 2017
Functional anatomy of the masking level difference, an fMRI study
David S Wack1, Jennifer L Cox, Claudiu V Schirda
1Buffalo Neuroimaging Analysis Center, Dept. of Neurology, University at Buffalo, Buffalo, New York, United States of America. dswack@buffalo.edu
Plos One
|August 1, 2012
Summary
Masking level differences (MLDs) involve detecting signals in noise with phase shifts. This study shows MLD processing involves thalamus-insula communication via the corpus callosum, impacting binaural hearing.
Area of Science:
- Auditory Neuroscience
- Neuroimaging
- Psychoacoustics
Background:
- Masking Level Differences (MLDs) assess hearing thresholds for signals in noise, varying interaural phase.
- Specific MLD conditions (N0Sπ, NπS0) improve signal detection by 10-20 dB compared to N0S0.
- Stimuli share identical spectral, level, and duration properties.
Purpose of the Study:
- To investigate the neural mechanisms underlying Masking Level Difference (MLD) processing.
- To identify brain regions involved in auditory signal detection with varying interaural phase.
- To explore the role of thalamocortical pathways in binaural hearing.
Main Methods:
- fMRI (sparse BOLD sequence) was used to image ten participants with significant MLDs (>10 dB).
- Stimuli consisted of band-pass noise (400-600 Hz) and an enveloped 500 Hz sine wave signal.
- Statistical brain maps were generated using SPM5 for second-level analysis.
Main Results:
- Significant activation was observed in the right pulvinar, corpus callosum, and bilateral insula for the NπS0-N0Sπ contrast.
- The left inferior frontal gyrus showed activation for N0Sπ-N0S0 and NπS0-N0S0 contrasts.
- Specific insular regions (right and left) were activated in contrasts comparing N0S0 with MLD conditions.
Conclusions:
- The thalamus acts as a gating mechanism for dichotic listening.
- MLD processing involves thalamic communication with the insula, utilizing the corpus callosum.
- Left inferior frontal gyrus activation suggests its role in the later stages of auditory processing for audibility improvement.
