I. Longitudinal changes in aging brain function

Abstract

Changes in brain activity over time were evaluated in a group of older adults in the Baltimore Longitudinal Study of Aging who maintained good physical and cognitive health. Participants underwent PET scans during rest and delayed verbal and figural recognition memory performance at year 1 baseline and at year 9. While memory performance remained stable over the 8 years, longitudinal changes in regional cerebral blood flow were observed within each scan condition. Further analyses revealed distinctive patterns of change related specifically to verbal or figural recognition, as well as longitudinal changes common to all scan conditions. These findings demonstrate that the older brain undergoes functional reorganization with increasing age in healthy, cognitively stable individuals. In view of the stable memory performance, the task-dependent results suggest that age-related changes in brain activity help maintain cognitive function with advancing age.

Figure 1

PET Session Order illustrates the progression of tasks during each scanning session. The order of verbal and figural task administration is counterbalanced across subjects. Task examples are shown for both recognition conditions. For both verbal and figural tasks, subjects are shown a list of stimuli to remember prior to scanning. During the recognition phase, the subject must indicate whether the test stimulus was one of the stimuli shown before. This phase is self paced, with the next stimulus appearing after the subject makes a response or after a maximum display time of 5000 ms.

Figure 2. Longitudinal Changes in Brain Activity

Differences in patterns of brain activity observed when comparing Year 1 to Year 9. Each example shows sagittal, coronal and axial projection images of the brain. The top row illustrates changes seen within each scan condition. The bottom row illustrates changes common to all scan conditions and those specific to verbal and figural recognition alone. Areas in blue illustrate significant decreases in rCBF; areas in red show significant increases in rCBF over time. The green line illustrates the z level of the representative slice shown in each condition.