We found differential effects of age on theta and gamma phase dynamics during working memory maintenance. We computed phase-locking value (PLV) from seed voxels in left temporal cortex to all other voxels in the brain in the theta band revealed by PAC (7–9 Hz). After correcting for multiple comparisons, the prefrontal cortex showed significant increased phase synchronization with left temporal cortex during memory maintenance compared to the non-memory control block (pcorrected < 0.01; Fig. 4a). However, this effect was only significant for younger adults. Older subjects exhibited no frontotemporal theta synchronization and their memory-specific PLV was significantly reduced relative to younger adults (Fig. 4a). In contrast, the same temporal cortex seeded connectivity analysis in the gamma band revealed a different pattern of results. A significant cluster (pcorrected < 0.01) of memory-related gamma PLV was detected in nearby regions (e.g., lateral occipital cortex) for both age groups, and did not differ across groups (Fig. 4b). Directionality analysis provided complementary support for these findings. Results from the theta band suggested prefrontal cortex was the sender and temporal cortex was the receiver for
