Abstract: A computer-implemented method for assisting a general anesthesia or a sedation of a subject, having receiving an electroencephalogram EEG signal of a subject, processing the EEG signal including ?-bands for defining for each instant of a plurality of instants, a part of the signal has in a time window having the instant, the part of the signal being related to the instant, determining for each instant, a distribution of a power of the part of the signal as a function of the frequency, determining for each instant a maximum power frequency as a frequency of maximum power in the distribution, the maximum power frequency being related to the instant, detecting a reference instant, so that the maximum power frequency as a function of time takes higher values before the reference instant than after, detecting in a time frame following the reference instant, an alpha instant corresponding to a first occurrence of a suppression of an ?-band, estimating a first parameter as the duration between the reference inst