Fig. 1

a Flowchart of the study selection process as carried out in accordance with the PRISMA guidelines. b Distribution of included publications over time, from year 2000 onwards. c Number of included publications by recording type (e.g., EEG, MEG, fMRI, or PET). Note that Pan and colleagues [14] included both EEG and fMRI recordings in their study. For that reason, panel (a) shows 24 studies but panels (b) and (c) indicates 25 recording modalities