Spectral power estimates for each participant were calculated in the following way: MEG sensors were grouped into different regions, corresponding to five major brain areas: frontal (17 sensors), central (29), occipital (29) and left and right temporal (28 each; Figure 3a). For each participant, spectral power was averaged over all sensors within each region, separately for the delta (0.5–4 Hz) and theta (4.5–7.5 Hz) frequency bands. This process resulted in a 53 (participants) × 2 (frequencies) × 5 (region) matrix of power estimates which were entered in subsequent regression analyses.
