Berger originally had intended to study astronomy. While he was serving in the German army in the early 1890s, his horse slipped down an embankment, nearly seriously injuring Berger. His sister many miles away had a feeling he was in danger and got her father to telegram him. This astonished him so much that he switched to study psychology.(Blakemore 1977)
He studied medicine at the University of Jena, receiving his doctorate in 1897. In 1900 he was hired as an assistant to Otto Ludwig Binswanger (1852-1929), chairman of the University's psychiatry and neurology clinic. There, he joined two famous scientists and physicians, Oskar Vogt (1870-1959) and Korbinian Brodmann (1868-1918) in their research on lateralization of brain function. He became a professor in 1906 and succeeded Binswanger in 1919. He later served as Rector at the University of Jena (1927-1928) and eventually became Professor Emeritus in Psychology in 1938.
Among his many research interests in neurology, Berger studied brain circulation, psychophysiology and brain temperature. However his main contribution to medicine and neurology was the systematic study of the electrical activity of human brain and the development of electroencephalography (EEG), following the pioneering work done by Richard Caton (1842-1926) in England with animals. In 1924, Berger made the first EEG recording in man and called it Electroenkephalogram. 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 (8-12 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). He also studied and described for the first time the nature of EEG alterations in brain diseases such as epilepsy.
His method involved inserting silver wires under the patients scalp, one at the front of the head and one at the back. Later he used silver foil electrodes attached to the head by a rubber bandage. As a recording device he first used the Lippmann capillary electrometer, but results were disappointing. He then switched to the string galvanometer and later to a double-coil Siemens recording galvanometer, which allowed him to record electrical voltages as small as one ten thousandth of a volt. The resulting output, up to three seconds in duration, was then photographed by an assistant.
"Berger, in 1935, was not regarded by his associates as in the front rank of German psychiatricists, having rather the reputation of being a crank. He seemed to me to be a modest and dignified person, full of good humour, and as unperturbed by lack of recognition as he was later by the fame it eventually brought upon him. But he had one fatal weakness: he was completely ignorant of the technical and physical basis of his method. He knew nothing about mechanics or electricity." - from The Living Brain, William Grey Walter.
International recognition came later to Berger. His results were confirmed by British and American scientists, such as Edgar Douglas Adrian and he was invited in 1937 to present his work to an international forum, where the importance and pioneering nature of his discoveries were hailed. Hans Berger thus earned the recognition of "Father of Electroencephalography."