Age-related changes in neural interactions during memory encoding and retrieval: A network analysis of PET data

Healthy young and old adults were PET-scanned while they were either encoding or recalling word-pairs. The right prefrontal cortex was more active during recall than during encoding in both groups, whereas a left prefrontal region showed a task x age interaction: it was more active during encoding than during recall in the young, but more active during recall than during encoding in the old. rCBF correlations between this region and the rest of the brain were different in the two groups. The most prominent difference occurred during recall in which a right frontopolar area was negatively correlated with the left prefrontal region in the young but positively correlated in the old. In general, the results suggest a reorganization of memory networks in the aging brain.