This paper describes the various electroencephalographic (EEG) patterns expressed by the comatose brain, starting with the sleep‐like oscillations associated with light coma. Deeper coma generally displays a burst‐suppression pattern characterized by alternating episodes of isoelectric (flat) EEG and bursting slow waves. The latter are the result of cortical hyperexcitability, as demonstrated by intracellular recordings in anesthetized animals. Further deepening of the coma yields to continuous isoelectric EEG and eventually results in a newly discovered type of spiky waves that have been termed ν‐complexes. They originate in the hippocampus as a result of intrinsically generated oscillations (ripples) in the delta range.