Ongoing brain activity that comprises action potentials and graded potentials like IPSP (inhibitory post synaptic potentials) and EPSP (excitatory post synaptic potentials) generated by a dynamically regulated collection of synapses on excitatory and inhibitory cells results in an ensemble field of electric activity that can be recorded non-invasively using scalp electrodes. Since the first recorded human electroencephalogram (EEG), pioneered in 1924 by Hans Berger (1873–1941) (Haas, 2003), digitization methods have revolutionized EEG acquisition, generating new methods of analysis. Three general approaches can be used to record and analyze these neuroelectric phenomena: (1) continuous EEG; (2) event-related potentials (ERPs); and (3) event-related oscillations (EROs).
