Evidence for reduced efficiency and successful compensation in older adults during task switching.

Older adults often show different functional activation patterns than younger adults in prefrontal cortex (PFC) when performing cognitive control tasks. These differences include age-related increases in PFC activation magnitude and reorganized PFC functional connectivity (fC) patterns. However, it remains unclear whether age-related alterations in brain activation patterns reflect a positive mechanism (e.g., compensatory response) or a sign of brain dysfunction (e.g., reduced efficiency). Here we used functional magnetic resonance imaging (fMRI) to compare PFC activation magnitudes and PFC connectivity patterns between younger and older adult groups during performance of a task switching paradigm. Results indicated age-related increases both in PFC activation magnitudes and in PFC fC with inferotemporal (IT) regions. However, these age-related fMRI increases were differentially associated with task performance. Whereas increased PFC activation magnitudes tended to be either unrelated to task RT or associated with poorer task performance, increased PFC-IT connectivity was associated with better task performance in older adults. Our results suggest that age-related reductions in efficiency and successful compensation can co-exist in older adults in the context of the same task.