Cortical aperiodic dynamics in hearing impairments predicts neural tracking of speech

Abstract

Excitation–inhibition balance is a fundamental property of cortical circuits, reflecting homeostatic plasticity that stabilizes neural activity in the face of functional disruption. This framework has been widely implicated in sensory deprivation and psychiatric disorders. In the auditory domain, it remains unclear how long-term bilateral and unilateral hearing loss reorganizes cortical E-I balance and how such reorganization affects speech processing. Here, we recorded resting-state EEG and measured spectral exponents as a noninvasive proxy for cortical E-I balance in individuals with bilateral hearing loss, single-sided deafness, and normal hearing. We found that spectral exponents differed systematically across hearing loss types. Participants with bilateral hearing loss exhibited reduced exponents, primarily in central-parietal regions, relative to normal-hearing controls, with a gradual increase with prolonged hearing-loss duration. In contrast, left- and right-sided deafness showed distinct patterns of hemispheric lateralization in spectral exponents. Participants also performed a naturalistic speech listening task, allowing quantification of neural tracking of speech. It showed stronger envelope tracking response for bilateral hearing loss group than normal control. Importantly, resting-state exponents across all hearing-impaired groups robustly predicted the strength of speech envelope tracking in noisy environments. These findings reveal dissociable patterns of aperiodic cortical dynamics following bilateral and unilateral auditory deprivation and highlight the homeostatic plasticity in supporting speech perception under challenging listening conditions.