English: Data are from publicly available source-localized resting-state MEG recordings.The experiment was approved by the UK National Research Ethics Service (South East Wales) and all participants gave written informed consent. One outlier participant was excluded due to an extremely large power increase for which we could not confirm that tiagabine was the sole cause. a Tiagabine induces clear increases in cortical oscillatory delta activity, as evidenced by the MEG power changes relative to placebo. The mean power change (red) induced by tiagabine is greatest at 3.3 Hz, featuring a more than 5-fold (430%) power increase from placebo. The largest power change we observed (after excluding one outlier, not shown here) was a 1200% power increase at 3.1 Hz. b The majority of participants (8/14) showed maximum power changes in the delta band (<4 Hz). The mean frequency of the maximum power change was 4.3 Hz, and the median frequency was 3.4 Hz. Image and figure description originally published in Frohlich et al. 2023 Communications Biology: https://doi.org/10.1038/s42003-023-04988-8