Biophysically detailed forward modeling of the neural origin of EEG and MEG signals

•Current dipoles are computed from biophysically detailed simulated neuron and network activity.•Extracted current dipoles allow for accurate computation of EEG and MEG signals in simplified and detailed head models.•Current-diplole approximation generally not suitable for accurate calculations of ECoG signals.•Method provides biophysics-based link between detailed neural activity and systems-level signals.