Large group differences in binaural sensitivity are represented in preattentive responses from auditory cortex

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Human Auditory Perception

Background:

• Interaural correlation (IAC) influences sound localization, with decorrelation causing perceived image widening.
• Significant variability exists in IAC thresholds among individuals, even those with normal hearing, raising questions about underlying causes.

Purpose of the Study:

• Identify listeners with normal versus impaired IAC resolution.
• Evaluate neural responses to IAC changes using electroencephalography (EEG).
• Model binaural processing to explain individual differences in IAC thresholds.

Main Methods:

• Recruited 19 subjects with normal audiometric profiles.
• Assessed IAC thresholds behaviorally.
• Measured scalp electrophysiological responses (N1, P2 amplitudes) and used source localization.
• Employed a binaural processing model.

Main Results:

• Eight participants exhibited poor IAC thresholds.
• Individuals with poor IAC thresholds showed significantly smaller N1 and P2 amplitudes.
• Electrophysiological differences were observed in auditory cortex regions.
• Binaural modeling suggested internal noise contributes to poor IAC resolution.

Conclusions:

• Electrophysiological evidence confirms a binaural processing deficit in some individuals with normal hearing and poor IAC thresholds.
• This deficit, potentially related to internal noise, may underlie conditions like hidden hearing loss.
• Cortical representation of binaural cues can be weak in affected individuals, even without subjective spatial hearing complaints.