Selection requirements during verb generation: differential recruitment in older and younger adults

Age-related differences in cognitive performance are well documented. These differences are most pronounced during tasks with high demands on cognitive control, and it has been proposed that selective alteration of prefrontal activity is associated with cognitive changes in old age. Here, differences in the neural systems underlying selection requirements for older and younger adults were investigated using functional magnetic resonance imaging (fMRI). A verb generation task was used, and selection requirements were varied with regard to whether each noun could be associated with either few (scissors-cut) or many (ball-bounce, kick, throw...) competing alternatives. The two age groups showed statistically equivalent behavioral performance across the task conditions but marked differences in activation. Across both age groups, high selection demands activated several regions including bilateral frontal, left anterior frontal, left inferior temporal regions, and the dorsal anterior cingulate cortex (ACC). Between-group comparisons using region-of-interest analyses revealed less activation for senior adults in left inferior frontal gyrus (IFG), left inferior temporal gyrus, and the anterior cingulate and higher activation in right inferior frontal gyrus compared to young adults. These findings indicate age-related changes in multiple regions contributing to aspects of selection requirements during verb generation.