More than a feeling: Expressive style influences cortical speech tracking in subjective cognitive decline

Subjective cognitive decline (SCD) doubles dementia risk. This study investigates how self-perceived cognitive worsening shapes neural dynamics during naturalistic speech perception. EEG was collected from 60 cognitively normal older adults as they listened to speech varied in prosodic contexts, categorized by expressive style (scrambled, descriptive, dialogue, exciting). Encoding models mapping three speech representations -- acoustic, subsyllabic segmentation and phonotactic features -- to ongoing EEG signals were built. Cortical tracking strength (CTS) showed that models fitted with subsyllabic linguistic features outperformed acoustic ones. Crucially, greater SCD severity was associated with weaker CTS of (1) subsyllabic linguistic but not acoustic features, and (2) prosodically flat speech (scrambled and descriptive). Thus, the CTS of higher-level linguistic features while listening to prosodically flat speech may serve as a potential neural marker for early-stage cognitive decline.