For almost a century, people have been fascinated and perplexed by the rhythmic electrical signals that can be detected on the surface of the head. Scientists call this the “electroencephalogram” or EEG, but “brainwaves” is the more commonly used description.

Brainwaves were observed first in humans by Hans Berger in the late 1920’s during his secretive work to understand the basis of extrasensory perception. He reasoned that these electrical signals might be transmitted like radio, allowing people to share each other’s thoughts. Although few scientists (then or now) shared this view, Berger’s discovery of the EEG changed clinical medicine. These recordings are invaluable in the management of diseases from brain tumors to sleep disorders.

Using the EEG he was also the first to describe the different waves or rhythms which were present in the normal and abnormal brain, such as the alpha wave rhythm (7.812–13.28 Hz), also known as “Berger’s wave”; and its suppression (substitution by the faster beta waves) when the subject opens the eyes (the so-called alpha blockade).