Processing speed mediates the relationship between brain structure and semantic fluency in aging

The present study has investigated how brain structure and processing speed contribute to age-related changes in semantic fluency. Groups of younger (N = 37) and older healthy participants (N = 40) completed a semantic fluency test and digit symbol test, and rested while diffusion tensor imaging (DTI) was performed. Group comparisons and correlational analysis revealed that age-related decline in semantic fluency was associated with reduction in gray matter volume in widespread fronto-temporal regions. Age-related decline in semantic fluency was also associated with decline in white matter integrity in brain tracts connecting these brain regions. Critically, hierarchical regression analysis suggested that low processing speed fully mediated the negative effects of lower gray matter volume and white matter integrity on semantic fluency. The present findings provide a support for the processing speed theory in relation to age related decline in semantic fluency, and also provide a reference for improving cognitive decline.

Automated summary

This study investigated the contribution of brain structure and processing speed to age-related changes in semantic fluency. The results showed that the decline in semantic fluency with age was associated with reductions in gray matter volume in widespread fronto-temporal regions and a decline in white matter integrity in brain tracts connecting these regions. Critically, low processing speed fully mediated the negative effects of lower gray matter volume and white matter integrity on semantic fluency. These findings support the processing speed theory in relation to age-related decline in semantic fluency and provide insights for improving cognitive decline.