Alpha wave

An 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.

In his 1929 paper Hans Berger called the larger, slower waves alpha waves and reported that they vanish when the eyes are opened^[1][2]. In 1934 Edgar Adrian and Bryan Matthews at Cambridge confirmed this and called it the Berger rhythm. It was largest at the back of the head, near the part of the brain that handles vision^[3].

It disappeared when the eyes were opened in a lit room, when the subject tried to make something out in the dark, or while the subject worked at a hard mental-arithmetic problem. Counting aloud, reciting familiar poetry or picturing shapes and figures barely changed it. In normal subjects its rate stayed between about 9.5 and 10.5 per second, and in three patients who had been blind for years it was absent^[3].

Adrian and Matthews read it as a patch of visual cortex beating in unison when it has nothing to do: the negative rather than the positive side of brain activity^[3].