Age-group differences in medial cortex activity associated with thinking about self-relevant agendas.

In this functional magnetic resonance imaging (fMRI) study, we compared young and older adults' brain activity as they thought about motivationally self-relevant agendas (hopes and aspirations, duties and obligations) and concrete control items (e.g., shape of USA). Young adults' activity replicated a double dissociation (M. K. Johnson et al., 2006): An area of medial frontal gyrus/anterior cingulate cortex was most active during hopes and aspirations trials, and an area of medial posterior cortex-primarily posterior cingulate-was most active during duties and obligations trials. Compared with young adults, older adults showed attenuated responses in medial cortex, especially in medial prefrontal cortex, with both less activity during self-relevant trials and less deactivation during control trials. The fMRI data, together with post-scan reports and the behavioral literature on age-group differences in motivational orientation, suggest that the differences in medial cortex seen in this study reflect young and older adults' focus on different information during motivationally self-relevant thought. Differences also may be related to an age-associated deficit in controlled cognitive processes that are engaged by complex self-reflection and mediated by prefrontal cortex.