Abstract
The scalp EEG consists of the summed electrical field potentials from cortical neurons. The EEG amplitude reflects the amount of synchronized activity in the underlying cortex, and the inter-electrode functional connectivity measures their interactions. The very fast oscillation reflects local process and narrow range interactions, and slow wave synchronization mediates long range interaction of largely separated cortical areas. In 1929, H. Berger first reported human EEG and deduced from the ceaseless electrical oscillations that “we have to assume that the central nervous system is always in a state of considerable activity” . In the mid-1990s, a series of PET and fMRI studies confirmed that the brain is far from idling when not engaged in a conscious activity, and the default-mode network (DMN) is active during resting/inattention state. The DMN is thought to be a neural basis of introspective processes such as self-referential processing. The scalp alpha wave is an electrophysiological candidate of the DMN function, and its sophisticated analysis might contribute to clarify common psychological features of various psychiatric disorders.
