Reduced listener-speaker neural coupling underlies speech understanding difficulty in older adults

An increasing body of studies have highlighted the importance of listener-speaker neural coupling in successful speech communication. How this mechanism may change with normal aging and the association of this change with age-related decline in speech understanding remain unexplored. In this study, we scanned with fMRI a young and an older speaker telling real-life stories, and then played the audio recordings to groups of young (N = 28, aged 19-27y) and older adults (N = 27, aged 58-75y) during scanning, respectively. The older listeners understood the story worse than the young, and the advancing age of the older listeners was associated with poorer speech understanding. Compared to the young listener-speaker dyads, the older dyads exhibited weaker neural couplings in both linguistic and extra-linguistic areas. Moreover, within the older group, the listeners age was negatively correlated with the overall strength of interbrain coupling, which in turn was associated with poorer speech understanding. These results reveal the deficits of older adults in achieving neural alignment with other brains, which may underlie the age-related decline in speech understanding.