3.2 Pathological aging effects (HA vs MCI group comparison)
3.2.1 Behavioral results. For RT (measured in ms), main effect of condition was significant, F (1,40) = 58.107, p< .001, with participants taking longer to respond to non-retrieval (mean RT = 1704, SD = 346) compared to retrieval (mean RT = 1439, SD = 257) conditions. Main effect of group was not significant,F (1,40) = 1.988, p = 0.166. No significant interaction between condition and group was found, F (1,40) = 0.146, p= 0.688. For accuracy, main effect of condition was significant,F (1,40) = 4.684, p = .036, with participants performing better on non-retrieval (mean accuracy = 86 %, SD = 11.9 %) compared to retrieval (mean accuracy = 82.2 %, SD = 8.3 %) conditions. Main effect of group was also significant, F (1,40) = 7.401, p = 0.01, with HA more accurate (mean accuracy = 87.24 %, SD = 7.5 %) than MCI (mean accuracy = 80.7 %, SD = 12 %). No significant interaction between condition and group was found, F (1,40) = 0.598, p= 0.444. Group averaged RT and accuracy scores for each condition are listed in Table 2 and plotted in Figure 1.
3.2.2 EEG results. Permutation tests on ERSPs (difference between retrieval and non-retrieval conditions) between HA and MCI showed two different effects. First, greater low beta ERS near the right frontal electrode (F2) from 444-481 ms post-stimulus onset was observed in retrieval compared to non-retrieval conditions for HA, t (21) = 3.136, p = 0.005, Cohen’s d = 1.01 (retrieval: 0.56 ± 1.51 dB, non-retrieval: -0.11 ± 1.34 dB), but not in MCI, t (19) = 1.292,p = 0.212 (retrieval: 0.24 ± 1.28 dB, non-retrieval: 0.65 ± 1.74 dB) (Figure 3.1). In addition, greater high beta ERS in the left fronto-temporal electrode (FT7) during 224-261 ms post-stimulus onset was observed in non-retrieval compared to retrieval conditions in MCI,t (19) = 2.173, p = 0.043, Cohen’s d = 0.83 (retrieval: 0.58 ± 0.58 dB, non-retrieval: 0.99 ± 0.93 dB), with a reverse pattern noted in HA, t (21) = 2.097, p = 0.048, Cohen’s d = 0.87 (retrieval: 1.03 ± 0.71 dB, non-retrieval: -0.65 ± 0.55 dB) (Figure 3.2).
For reference, group-averaged ERSPs in different frequency bands in each condition is illustrated in Supplementary Figures 2 (HA) and 3 (MCI). The differences in ERSPs between conditions within each group are included in Supplementary Figures 5 (HA) and 6 (YA). Results from all time frames (including windows with non-significant effects) for pathological aging effects (HA versus MCI) can be found in Supplementary Figure 8.