Deficits in process-specific prefrontal and hippocampal activations contribute to adult age differences in episodic memory interference.

The ability to distinguish currently relevant from familiar but irrelevant memories is important in everyday life. We used functional magnetic resonance imaging to examine the neural correlates of age differences in the ability to withstand interference from similar past events. Younger and older adults worked on a continuous recognition task consisting of 3 consecutive runs. Each run was composed of the same set of word pairs, and participants were instructed to recognize word pair repetitions within runs. The monitoring demands associated with rejecting familiar, but currently irrelevant information were assumed to increase over consecutive runs. Over runs, older, but not younger adults showed decline in memory performance, whereas younger, but not older adults showed increasing engagement of anterior prefrontal cortex. Individual differences in cortical thickness and task-related activation of anterior prefrontal areas predicted performance differences within and across age groups. Compared with younger adults, older adults also showed a reduced hippocampal response to novel associations of familiar stimuli. We conclude that monitoring deficits due to impaired involvement of prefrontal regions and reduced hippocampal responses to associative novelty contribute to aging-related deficits in disambiguating the contextual information of familiar events.