Ongoing brain functioning in the form of electrophysiological activity can be recorded non-invasively using scalp electrodes. The German physiologist and psychiatrist Hans Berger (1873-1941) first recorded the human EEG in 1924 [44]. Scalp-recorded electrophysiological activity consists of three distinct methods: 1) EEG: frequency-dependent, spontaneous and continuous neural activity during a restful or specific mental state, 2) ERPs: time-locked, trial-averaged, and task-specific electrophysiological activity during a specific sensory/motor/cognitive event, and 3) EROs: time-frequency (TF) measures of brain electrical activity during a specific sensory/motor/cognitive event.
