Alpha oscillations in brain functioning: An integrative theory

Author(s): Schurmann, M., BasarEroglu, C., Karakas, S.

Journal/Book: Int J Psychophysiol. 1997; 26: PO Box 211, 1000 AE Amsterdam, Netherlands. Elsevier Science BV. 5-29.

Abstract: The old concept stating that EEG alpha (10-Hz) activity reflects passive or idling states of the brain is giving way to modern views of 10-Hz oscillations in relation to diverse brain functions comprising sensory, motor, and memory processes: (1) Spontaneous alpha activity is not pure noise as shown by methods of chaos analysis. (2) Evoked alpha oscillations patterns (precisely time-locked to a stimulus; duration approx. 200-300 ms) depend on the modality of stimulation and the recording site. (3) Induced alpha oscillations are initiated by, but not closely time-locked to a stimulus. (4) 10-Hz oscillations are recorded in nervous systems of different complexities, from the human brain to isolated ganglia of invertebrates. The neural origins of 10-Hz oscillations are demonstrated by recordings at the cellular level. (5) Rather than trying to locate a unique alpha generator, it is preferable to assume that a 'diffuse and distributed alpha system' exists. A particular support for this hypothesis is given by stimulus-dependent hippocampal alpha responses in the cat brain. (6) The major physiological meaning of 10-Hz oscillations may be comparable to the putative universal role of gamma responses in brain signaling.

Note: Review Basar E, Univ Lubeck, Inst Physiol, D-2400 Lubeck, GERMANY

Keyword(s): evoked potential; event-related potential; EVENT-RELATED DESYNCHRONIZATION; COMPOUND FIELD POTENTIALS; EVOKED-POTENTIALS; HEMISPHERIC-DIFFERENCES; 3-YEAR-OLD CHILDREN; NEOCORTICAL NEURONS; RETICULAR-FORMATION; EEG RHYTHMICITIES; VISCERAL GANGLION; AUDITORY PATHWAY

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