Patients were sedated with propofol during surgery. Due to the retrospective nature of this study, there was no standardized protocol to control the amount of anaesthesia while recording ECoG. As the level of sedation might influence the ECoG, the burst suppression ratio (BSR) of the recordings was calculated and used as a covariate in the analysis (See Figure S1 for an example of used ECoG data). The BSR is the sum of all the regions showing at least 0.5 seconds of suppression, divided by the total length of the epochs (40.95 s). Suppression was defined as a region with very low ECoG activity, using 5 microV as threshold value [22].
