An electroencephalogram (EEG) is a graphic picture of the electrical activityof the brain. This visual image is created when electrodes are placed on a subject's scalp and connected by wires to an electroencephalograph, a devise which records the patterns of brain waves--the rhythmic changes in electric potentials in the brain--by tracing them with a fine, inked needle or nib onto a sheet of paper. EEGs are useful in diagnosing epilepsy, brain tumors, strokes, brain damage caused through head trauma, and other neurological conditions characterized by distinctive, abnormal brain wave patterns. They are also used in investigating psychiatric disorders such as schizophrenia, and in determining brain death--an important process for use in conjunction with organ donation for surgical transplant recipients. The founder of electroencephalography was Hans Berger (1873-1941), a German psychiatristwho made the first human EEG in 1924. Interested primarily in psychophysiology--that is, the relationship between the mind and the brain--Berger set aboutmeasuring the brain's electrical activity in the hope that a physiological record of this kind would provide insight into mental processes. He found inspiration for his work in the electrocardiograph (ECG) invented by Willem Einthoven in 1900, and in work done earlier on the brain waves of animals. In 1875, Richard Caton (1842-1926), an English physiologist and surgeon, had measured electrical activity in the exposed brains of rabbits and monkeys but had been unable to make a graphic recording; the first recording of this kind was made in 1913 by a scientist named Vladimir Pravdich-Neminskii, who used the Einthoven string galvanometer to record from the intact skulls of dogs. Using agalvonometer much like the one Pravdich-Neminskii had used a decade earlier,Berger began his search for the human EEG by experimenting with the exposedbrains of dogs. He then started placing needle electrodes under the scalp ofpatients who had lost some of their skull bones in surgery. It was while working with one of these patients--a seventeen-year-old who had been operated onbecause of a suspected brain tumor--that Berger recorded the first human EEGin 1924. He was initially uncertain whether the electrical oscillations he recorded originated in the brain. It was not until after conducting many otherexperiments--including experiments on the intact skulls of healthy people and of people with brain disorders--that he published his first paper on the human electroencephalogram in 1929. The initial reaction of other scientists toBerger's work was one of disbelief; like Berger himself, the scientific world at first doubted whether the workings of an organ as complex as the brain could be recorded through the skull. Berger did not achieve an international reputation until 1934, when Edgar Douglas Adrian (1889-1977), a renowned English neurophysiologist, confirmed his findings. Even then, however, Berger remained unappreciated in his own country. In the late 1930s, the Nazis forced him to retire from the University of Jena, where he had been professor and director of psychiatry since 1919. With his laboratory dismantled and no facilities to carry on his work, Berger fell into a depression and committed suicide in 1941.
Despite his reputation as a reserved and inflexible man, Berger would no doubt be pleased to know that, over the years, research scientists have used theEEG to identify the parts of the brain involved in the mental processes of reasoning, memory, and feeling. He would also, no doubt, be interested in a system that has simplified EEG interpretation. Known as BEAM (brain electrical activity mapping), this system was invented by Frank Duffy of the Harvard Medical School in the early 1980s. It uses computer technology to combine the signals from the individual electrodes into a overall, color-coded map of the brain's electrical activity. BEAM can store large amounts of EEG data, comparehealthy profiles with abnormal ones, and provide detailed analyses that havebeen used to accurately diagnose such conditions as dyslexia and schizophrenia, which are usually difficult to detect. Efforts are currently underway to use BEAM in matching EEG patterns to specific brain functions. For example, research scientists at Johns Hopkins University have used BEAM to map the electrical activity involved in the movement of a monkey's arm; their studies haveshown that when the monkey anticipates moving its arm, the pattern of electrical activity in its brain changes. If efforts like these are successful, itmay one day be possible to use computers and the electrical activity of the brain not only to control artificial limbs but in many other revolutionary applications as well.
The use of EEGs in neurofeedback (or biofeedback) is becoming increasingly popular; for example, in helping children cope with Attention Deficit/Hyperactivity Disorders. In 1997, Neuropathways EEG Imaging system became the first U.S. patented digital EEG neurofeedback device, displaying brain wave voltages and frequencies in real time, (there is less than one thousandth of a second delay between when the brain wave begins and its display on a computer screen). This allows interventional feedback when the event is occurring, not after it has passed, and has produced improvement in concentration and other cognitive functions of both ADD clients and head trauma victims. Meanwhile, Mind Media in The Netherlands is marketing The BrainTracer, anon-medical device which allows individuals to see their real time brain waveactivity on standard home computer screens and print them on standard printers.