Neural mechanisms of lipreading in the Polish-speaking population: effects of linguistic complexity and sex differences

Lipreading, the ability to understand speech by observing lips and facial movements, is a vital communication skill that enhances speech comprehension in diverse contexts, such as noisy environments. This study examines the neural mechanisms underlying lipreading in the Polish-speaking population, focusing on the complexity of linguistic material and potential sex differences in lipreading ability. Cohort of 51 participants (26 females) underwent a behavioral lipreading test and an fMRI-based speech comprehension task, utilizing visual-only and audiovisual stimuli, manipulating the lexicality and grammar of linguistic materials. Results indicated that males and females did not differ significantly in objective lipreading skills, though females rated their subjective abilities higher. Neuroimaging revealed increased activation in regions associated with speech processing, such as the superior temporal cortex, when participants engaged in visual-only lipreading compared to audiovisual condition. Lexicality of visual-only material engaged distinct neural pathways, highlighting the role of motor areas in visual speech comprehension. These findings contribute to understanding the neurocognitive processes in lipreading, suggesting that visual speech perception is a multimodal process involving extensive brain regions typically associated with auditory processing. The study underscores the potential of lipreading training in rehabilitating individuals with hearing loss and informs the development of assistive technologies.