Age-dependent contribution of domain-general networks to semantic cognition

Aging is characterized by a decline of cognitive control. In semantic cognition, this leads to the paradox that older adults usually show poorer task performance than young adults despite their greater semantic knowledge. So far, the underlying neural changes of these behavioral differences are poorly understood. In the current neuroimaging study, we investigated the contribution of domain-general networks to a verbal semantic fluency task in young and older adults. In both age groups, task processing was characterized by a strong positive integration within the multiple-demand as well as between the multiple-demand and the default mode system during semantic fluency. However, the behavioral relevance of strengthened connectivity differed between groups: While within-network functional connectivity in both networks predicted greater efficiency in semantic fluency in young adults, it was associated with a slower performance in older adults. Moreover, only young adults profited from increased connectivity between networks for their semantic memory performance. Our results suggest that the functional coupling of usually anti-correlated networks is critical for successful task processing, independent of age, when access to semantic memory is required. Furthermore, our findings lend novel support to the notion of reduced efficiency in the aging brain, due to neural dedifferentiation in semantic cognition.