An alpha wave is a brain-wave pattern associated with relaxed wakefulness and typically oscillating at about 8–13 hertz.
Alpha waves are electrical rhythms measured with electroencephalography, or EEG. They are especially prominent over the posterior parts of the head when a relaxed person is awake with their eyes closed. Opening the eyes or concentrating on a task often reduces this rhythm, a change historically called alpha blocking or desynchronization.
The rhythm was first described in human EEG research by German psychiatrist Hans Berger, whose pioneering recordings were published in the late 1920s. Berger initially called the pattern the “Berger rhythm” before the term alpha became standard.
Alpha activity does not mean that the whole brain is inactive. It reflects coordinated network activity and changes with attention, arousal, age, medication, and disease. EEG bands overlap somewhat in frequency, so alpha should not be treated as a single universal mental state. Delta, theta, beta, and gamma describe other commonly used frequency ranges.