Neurovascular decoupling and compensatory network recruitment during speech perception in aging: evidence from EEG-fNIRS

Age-related decline in speech perception is a prominent challenge in auditory aging, especially under noise conditions. However, how neural and neurovascular processes are jointly organized and coordinated across adulthood during speech perception remains incompletely characterized. This study employed simultaneous electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) to investigate neural activation, functional connectivity, and neurovascular coupling across youth (n = 20, aged 28.8 ± 5.7), middle-aged (n = 23, aged 48.0 ± 6.5) and older (n = 23, aged 65.8 ± 3.7) adults with normal hearing. Participants performed speech perception tasks under quiet and noisy listening conditions, with signal-to-noise ratio (SNR) levels of 5 dB and − 5 dB. Behaviorally, speech recognition performance declined significantly with age under noise conditions but remained preserved in quiet. fNIRS results revealed increased activation and enhanced functional connectivity across frontal-motor and temporal regions in older adults, indicating compensatory recruitment during speech perception in noise. EEG analysis showed age-related reductions in low-frequency (delta, theta, and alpha) power, particularly in motor and auditory-speech areas, reflecting impaired auditory and cognitive processing. Neurovascular coupling analysis further revealed an age-related shift from predominantly positive to negative correlations between EEG power and fNIRS activation, suggesting age-related differences in neurovascular coordination across the adult lifespan. Together, these findings delineate a multilevel pattern of compensatory and maladaptive processes associated with age-related speech perception decline. By integrating electrophysiological and hemodynamic evidence within a unified framework, this study refines existing models of auditory-cognitive aging and highlights age-related alterations in neurovascular coordination that may be relevant for understanding variability in speech processing in older adults.