Envelope following responses predict speech-in-noise performance in normal-hearing listeners

Area of Science:

• Auditory Neuroscience
• Neuroscience
• Otoacoustic Emissions

Background:

• Permanent hearing loss stems from sensory cell loss, often preceded by synaptic degeneration between sensory cells and auditory nerve fibers.
• This neural degeneration, known as cochlear synaptopathy, can degrade auditory processing and speech comprehension in noise.
• While Auditory Brainstem Response (ABR) amplitudes quantify synaptopathy in mice, their variability in humans limits clinical utility.

Purpose of the Study:

• To investigate the utility of Envelope Following Responses (EFRs) to rectangularly modulated tones as a more robust measure of cochlear synaptopathy in humans.
• To correlate EFR measures with speech recognition performance in individuals with normal audiometric thresholds.

Main Methods:

• Participants with normal hearing underwent speech recognition tasks and EFR measurements using stimuli modulated by rectangular and sinusoidal envelopes.
• Electrophysiological responses (EFRs) were analyzed for correlations with word recognition scores.

Main Results:

• Higher harmonics of EFR magnitudes evoked by rectangular envelope modulation significantly correlated with word recognition scores.
• EFRs evoked by sinusoidal modulation did not show a significant correlation with word recognition performance.
• Individual differences in synaptopathy may explain speech recognition variability in individuals with normal hearing thresholds.

Conclusions:

• Rectangular envelope modulation of carrier tones offers a promising method for detecting cochlear synaptopathy in humans.
• This approach may help identify individuals with subclinical neural damage contributing to hearing difficulties, particularly in noisy environments.
• Findings support the role of cochlear neural integrity in speech recognition abilities beyond standard audiometric measures.