Noise-reduced MEG data underwent standard data preprocessing procedures using Brain Electrical Source Analysis software (BESA version 7.0). This included visual inspection for large artifacts, such as cardiac and blink artifacts, which were corrected for using signal-space projection (SSP53,54, and coregistration of each participant’s MEG data with their structural T1-weighted MRI data. The MEG data were then split into 2000 ms epochs (− 500 to 1500), with 0.0 s defined as stimulus grid onset. Epochs containing artifacts were then rejected using a fixed threshold method based on participant-specific amplitude and gradient thresholds. In addition, we confirmed that the number of correct trials analyzed did not significantly differ by AUD and CUD, including covarying for sex and age (AUD: F(1,40) = 2.23, p = 0.143; CUD: F(1,40) = 0.31, p = 0.581), which helps ensure that the signal-to-noise ratio was comparable between groups.
