Magnetoencephalography (MEG) systems use superconducting electronics and magnetic shielding to detect the magnetic fields generated by synaptic neuronal activity. This chapter focuses on two types of quantitative analyses of human electrophysiological data: spectral analysis methods and evoked potentials. Spectral analysis of Electroencephalography (EEG) and MEG signals across multiple sensor locations reveals clear spatial patterns. EEG and MEG activity can be subdivided into three major subdivisions: spontaneous activity, evoked responses, and induced responses. Evoked responses are time domain averages across multiple trials of a repeating stimulus or response. Electroencephalographic and MEG methods based on time-frequency transformation are usually concerned with capturing changes in the brain's oscillatory phenomena produced by stimuli, mental events, or responses. A valid measure of connectivity between regions of the brain engaged in the same cognitive process or behavior is among the most highly prized uses of EEG and MEG data.