Electroencephalogram
A recording of the brain's electrical fluctuations, usually through electrodes on the head. The German psychiatrist Hans Berger reported human recordings in 1929 and named them the Elektrenkephalogramm.
Berger began trying to record the brain's electricity in 1910. On 6 July 1924 he recorded electrical fluctuations from the surface of the brain of a 17-year-old patient whose skull had been opened by a surgeon, now counted as the first human EEG[2]. In his 1929 paper he named the record the Elektrenkephalogramm, calling the larger, slower waves alpha waves and the smaller, faster ones beta waves[1][3].
The EEG made it possible to tell, from the shape of the trace alone, whether a person was awake, asleep, or had briefly lost consciousness, without asking them. In December 1934 Frederic Gibbs, Hallowell Davis and William Lennox recorded, during petit mal attacks in which consciousness lapses, a spike and a rounded wave repeating about three times a second[3].
Yet in 1934 Edgar Adrian and Bryan Matthews reported that picturing shapes and figures left the alpha rhythm unchanged[4]. What the EEG captured was the level of consciousness, how awake a person was, not its content: what they were seeing or imagining.
Related terms
- Alpha waveAn EEG rhythm of about ten waves a second, strongest at the back of the head when a person rests with the eyes shut. Berger named it in 1929 and reported that it vanishes when the eyes open.
- Reticular formationThe core of the brainstem, where nerve cells and fibers interlace like a net. In 1949 Giuseppe Moruzzi and Horace Magoun reported that stimulating it turns the EEG into the pattern of waking.
- REM sleepPeriods of sleep in which both eyes move together in rapid jerks. Eugene Aserinsky and Nathaniel Kleitman reported them in 1953; sleepers woken during them usually described detailed dreams.
Sources
- H. Berger, “Über das Elektrenkephalogramm des Menschen,” Archiv für Psychiatrie und Nervenkrankheiten 87, 527–570 (1929).
- F. Brigo, V. Gazzaniga, S. Iorio and M. Martini, “Mirroring the mind and brain: reflections on Hans Berger's EEG and the scientific perception of reality,” Medicina nei Secoli 36(3), 171–174 (2024).
- J. L. Stone and J. R. Hughes, “Early history of electroencephalography and establishment of the American Clinical Neurophysiology Society,” Journal of Clinical Neurophysiology 30(1), 28–44 (2013).
- E. D. Adrian and B. H. C. Matthews, “The Berger rhythm: potential changes from the occipital lobes in man,” Brain 57(4), 355–385 (1934).