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Human frequency-following responses to binaural masking level difference stimuli
James R Wilson1, Ananthanarayan Krishnan
1Department of Audiology and Speech Sciences, Purdue University, West Lafayette, IN 47907, USA.
Journal of the American Academy of Audiology
|April 23, 2005
Summary
This study investigated the brainstem
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Psychoacoustics
Background:
- Binaural masking level difference (MLD) is crucial for auditory perception.
- Previous studies show MLD effects in event-related potentials but not brainstem responses.
- The frequency-following response (FFR) reflects low-frequency, phase-locking neural activity.
Purpose of the Study:
- To investigate physiologic masking level differences using human frequency-following responses.
- To determine if brainstem auditory evoked potentials reflect MLD phenomena.
Main Methods:
- Recorded unmasked and masked FFRs to 500 Hz tone bursts in nine normal-hearing adults.
- Used a 1.5 kHz low-pass masker.
- Compared FFRs across diotic (SoNo) and dichotic (SpiNo, SoNpi) conditions.
Main Results:
- FFR amplitude significantly reduced in the diotic (SoNo) condition compared to the unmasked condition.
- Significant FFR amplitude recovery observed in dichotic conditions (SoNpi and SpiNo).
Conclusions:
- Brainstem frequency-following responses demonstrate physiologic masking level differences.
- Results support the role of phase-locked neural activity in brainstem mechanisms of masking release.