Musical expertise enhances neural alignment-to-young in sensorimotor regions that predicts older adults' audiovisual speech-in-noise perception

Musical training can offset age-related decline in speech-in-noise perception. However, how lifelong musical expertise affects the functional reorganization of older brain in speech-in-noise perception has not yet been systematically investigated. Here, we address this issue by analyzing fMRI responses of older musicians, older non-musicians and, young non-musicians identifying noise-masked audiovisual syllables. First, we confirmed that older musicians outperformed older non-musicians and even equaled young non-musicians. Then, we showed that both older groups showed decreased auditory activation and increased visual activation compared to young non-musicians, while older musicians showed higher activation in speech motor regions and greater deactivation of default mode network (DMN) regions than older non-musicians. Next, we revealed that musical expertise counteracted the age-related neural dedifferentiation of speech representation, making older musicians exhibit higher neural alignment-to-young in bilateral sensorimotor areas. Finally, we disentangled that greater activation in speech motor areas and stronger deactivation in DMN regions were correlated with higher neural alignment in sensorimotor areas, which strongly predicted better performance in older adults. Together, long-term musical expertise mitigates age-related deficits in audiovisual speech-in-noise processing through enhanced compensatory scaffolding that reserves youth-like representation in sensorimotor areas. Our findings provide a comprehensive perspective on understanding age- and experience-related brain reorganization during speech perception.