Age effects on the neural correlates of episodic retrieval: increased cortical recruitment with matched performance.

Functional neuroimaging investigations have revealed a range of age-related differences in the neural correlates of episodic memory retrieval. Typically, whereas activity is reduced in older compared with younger adults in some regions, other regions are engaged exclusively, or to a greater extent, in older adults. It is unclear whether such differences merely represent the neural correlates of the lower levels of memory performance and impaired recollection typical of older adults. This issue was addressed in the present event-related functional magnetic resonance imaging study. The level of recollection was matched between groups of healthy younger and older adults for a subset of picture items in a source memory task by manipulating the number of study presentations. Contrasts of the activity elicited by old items attracting correct source judgments and correctly identified new items revealed that the 2 groups recruited many of the same brain regions. However, a striking pattern of age-related differences was also observed. In older adults, retrieval-related increases in activity were more widespread and of greater magnitude than in the young. Moreover, regions demonstrating retrieval-related decreases in activity were almost absent in the older participants. These findings suggest an age-related decline in the efficiency with which neural populations support cognitive function.