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Peripheral phoneme encoding and discrimination in aging and hearing impairment
Marjoleen Wouters1, Etienne Gaudrain2, Konrad Dapper3
1Hearing Technology at Wireless, Acoustics, Environment and Expert Systems, Department of Information Technology, Ghent University, Technologiepark 126, 9052, Zwijnaarde, Belgium.
Hearing Research
|July 20, 2026
Summary
Aging and hearing loss impair speech perception by affecting neural encoding. This study reveals how cochlear synaptopathy and outer hair cell damage impact temporal envelope and fine structure processing, crucial for understanding speech in noise.
Area of Science:
- Auditory Neuroscience
- Speech Perception
- Neuroscience
Background:
- Speech perception in noise is challenging for older adults, hearing-impaired individuals, and even some younger adults with normal hearing.
- Aging and cochlear damage can lead to difficulties in processing auditory information, impacting speech understanding.
Purpose of the Study:
- To investigate the effects of aging, cochlear synaptopathy (CS), and outer hair cell (OHC) damage on speech encoding and phoneme discrimination.
- To differentiate the roles of temporal envelope (TENV) and temporal fine structure (TFS) encoding in auditory perception.
Main Methods:
- Recorded electroencephalography (EEG) based envelope-following responses (EFRs) to amplitude-modulated tones and phoneme pairs targeting TENV and TFS.
- Assessed behavioral phoneme discrimination in quiet and noise (ipsilateral and contralateral).
- Examined participants across different age groups and hearing statuses.
Main Results:
- Envelope-following response amplitudes decreased with age, indicating emerging CS.
- High-frequency TENV-based EFRs were reduced in older, hearing-impaired individuals with combined CS and OHC damage.
- TFS-based phoneme discrimination worsened with OHC loss and age, while TENV-based discrimination remained unaffected by age.
Conclusions:
- Neural coding deficits, particularly in TFS processing, contribute to speech perception difficulties, even with normal audiometric thresholds.
- Combining electrophysiological and behavioral measures can help detect subclinical auditory deficits.
- This research provides a framework for diagnosing age-related and hidden hearing loss earlier.
