We ran several analyses to confirm the validity of the main findings. First, we assessed spectral power. It is possible that the effects of age or stimulation altered spectral power in the same frequencies and electrodes or voxels involved in PAC, thereby changing signal-to-noise ratio and phase estimation quality. However, we found no significant changes in baseline-corrected mean power values across the delay period (500 to 3000 ms post-target onset) between blocks for either age group or stimulation condition (7–9 Hz electrodes, ts41 < 1.334, ps > 0.189, dsz < 0.206; 7–9 Hz voxels, ts41 < 1.090, ps > 0.282, dsz < 0.168; 26–34 Hz electrodes, ts41 < 0.849, ps > 0.401, dsz < 0.131; 26–34 Hz voxels, ts41 < 0.999, ps > 0.324, dsz < 0.154). Further, there were no significant changes in signal-to-noise ratios in memory-related EEG at the frequencies, electrodes, or voxels involved in PAC between age groups or stimulation conditions (ts41 < 1.325, ps > 0.193, dsz < 0.204). Of note, while age-related rotations in 1/f spectra have been previously observed in parietal and central midline
