Interaural frequency mismatch jointly modulates neural brainstem binaural interaction and behavioral interaural time...

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Biomarkers

Background:

• The binaural interaction component (BIC) of the auditory brainstem response (ABR) measures binaural processing.
• Spectral mismatching of auditory inputs can impair binaural hearing, particularly interaural time difference (ITD) sensitivity.
• The BIC's potential as a biomarker for detecting such spectral mismatches is of interest.

Purpose of the Study:

• To investigate the impact of interaural frequency mismatch (IFM) on the BIC.
• To assess how IFM affects behavioral ITD sensitivity in humans.
• To explore the relationship between BIC, ITD perception, and IFM.

Main Methods:

• Recorded binaural and monaural ABRs in response to narrowband tones with varying IFM.
• Computed BIC from ABRs.
• Measured ITD discrimination thresholds using psychophysical lateralization tasks with the same stimuli.
• Analyzed effects of IFM and sound level on BIC and ITD thresholds.

Main Results:

• IFM significantly reduced BIC amplitudes compared to frequency-matched conditions.
• Behavioral ITD discrimination thresholds were elevated with IFM, especially at lower sound levels.
• IFM's effect on ITD thresholds was more pronounced at lower sound levels.
• Empirically measured BIC and model predictions aligned with perceptual boundaries for fused and lateralized sounds.

Conclusions:

• BIC is sensitive to interaural frequency mismatch.
• IFM degrades ITD sensitivity, particularly at lower sound levels.
• The BIC may serve as a biomarker for detecting spectral mismatches that affect binaural hearing and sound localization.