Alpha waves are electromagnetic oscillations in the frequency range of 8–12 Hz arising from synchronous and coherent (in phase / constructive) electrical activity of thalamic pacemaker cells in the human brain. They are also called Berger's wave in memory of the founder of EEG .
Alpha waves are one type of brain waves, commonly detected by electroencephalography (EEG) or magnetoencephalography (MEG) and predominantly found to originate from the occipital lobe during periods of waking relaxation with the eyes closed. Conversely alpha waves are attenuated with open eyes as well as by drowsiness and sleep. They are thought to represent the activity of the visual cortex in an idle state. Occipital alpha waves during periods of eyes closed are the strongest brain signals of the EEG. They usually can be detected with the naked eye.
An alpha-like normal variant called mu (μ) is sometimes seen over the motor cortex (central scalp) and attenuates with movement, or even with the intention to move.