Overrecruitment in the aging brain as a function of task demands: evidence for a compensatory view.

This study used fMRI to investigate the neural effects of increasing cognitive demands in normal aging and their role for performance. Simple and complex go/no-go tasks were used with two versus eight colored letters as go stimuli, respectively. In both tasks, no-go stimuli could produce high conflict (same letter, different color) or low conflict (colored numbers) with go stimuli. Multivariate partial least square analysis of fMRI data showed that older adults overengaged a cohesive pattern of fronto-parietal regions with no-go stimuli under the specific combination of factors which progressively amplified task demands: high conflict no-go trials in the first phase of the complex task. This early neural overrecruitment was positively correlated with a lower error rate in the older group. Thus, the present data suggest that age-related extra-recruitment of neural resources can be beneficial for performance under taxing task conditions, such as when novel, weak, and complex rules have to be acquired.