Jena, Weimar Republic (now in Germany)
By the latter part of the nineteenth century, the field of psychophysiology had fallen into disrepute among neurologists and psychiatrists. Two new approaches had become fashionable: the neoanatomical approach of Bernhard Friedrich A. Gudden, Theodor H. Meynert, Paul E. Flechsig, Auguste Henri Forel, and Constantin von Monakow and the functional approach exemplified by the work of Emil Kraepelin, Eugen Bleuler, Sigmund Freud, Max Adler, and Carl Jung. Hans Berger, however, was not attracted by either of these two avenues of research. The former was not functional enough to satisfy his psychophysiological interests, and the latter, in his opinion, lacked a firm foundation in the natural sciences, which he regarded as indispensable to the understanding of brain function and its relation to mental processes. From the outset of his career, Berger chose the difficult position of the outsider, a position in which he was to remain.
As a scientist, Berger’s search for the human electroencephalogram, or EEG (English physiologist Richard Caton described the electroencephalogram, or “brain wave,” in rabbits and monkeys in 1875), was motivated by his desire to find a physiological method that might be applied successfully to the study of the long-standing problem of the relationship between the mind and the brain. His scientific career, therefore, was directed toward the elucidation of the psychophysical relationship in terms of principles that would be rooted firmly in the natural sciences and would not have to rely on vague philosophical or mystical ideas.
During his early career, Berger attempted to study psychophysical relationships by plethysmographic measurements of changes in the brain circulation of patients with skull defects. In plethysmography, an instrument is used to indicate and record by tracings the variations in size of a part of the body. Later, Berger investigated temperature changes occurring in the human brain during mental activity and the action of psychoactive drugs. He became disillusioned, however, by his inability to generate meaningful psychophysical understanding through these investigations.
Next, Berger studied the electrical activity of the brain and, in the 1920’s, set out to search for the human electroencephalogram. He believed that the EEG would finally provide him with a physiological method capable of furnishing insight into mental functions and their disturbances. In 1920, Berger made his first unsuccessful attempt at recording the electrical activity of the brain from the scalp of a bald medical student. At that time, he modified his methods of research and attempted to stimulate the cortex of patients with skull defects by applying an electrical current to the skin covering the defect. The main purpose of these stimulation experiments was to elicit subjective sensations. Berger hoped that eliciting these sensations might give him some clue about the nature of the relationship between the physiochemical events produced by the electrical stimulus and the mental processes revealed by the patients’ subjective experience. According to his diaries, the availability of many patients with skull defects—in whom the pulsating surface of the brain was separated from the stimulating electrodes by only a few millimeters of tissue—reactivated Berger’s interest in recording the brain’s electrical activity.
At the time of these experiments, Berger had very little electrophysiological experience, and his knowledge of physics and instrumentation was limited. In addition, the instruments available to him were not well suited to the research he was contemplating. Nevertheless, he conducted his first electrical recordings from skull defects in 1924 by using the large Edelmann string galvanometer, an instrument that had been designed to record electrocardiograms, or electrical charts measuring heart activity. In 1926, he acquired the new Siemens coil galvanometer, an apparatus that also was used in electrocardiography.
In 1932, the Siemens Company constructed an oscillograph with an amplifier for Berger. This instrument had adequate gain and, in contrast to the earlier galvanometers, was a voltage-measuring, rather than a current-measuring, device. All of these instruments were used in conjunction with an optical recording system in which electrical oscillations caused a mirror to deflect a projected beam of light beam. The deflections of the light beam were proportional to the magnitude of the electrical signals. The movement of the spot of the light beam was recorded on photographic paper moving at a speed of three centimeters per second; occasionally, slower speeds were used. The paper width was twelve centimeters, and the lengths of the records varied between about three and eight meters.
During his investigations, Berger remained faithful to his old recording instruments, even when better methods and equipment—such as cathode-ray oscillography or Tönnies’s ink-writing oscillograph—became available. In the 1930’s, Berger hoped that Siemens would provide him with a multiple oscillograph system, but this hope remained unfulfilled. Thus, to the end of his career, whenever he wished to record with more than one channel at a time, he was forced to use the Siemens oscillograph and the coil galvanometer simultaneously. A major problem with this method, however, was that the gains of the two instruments were very different; thus it was difficult to place the light spots of the two systems in precise vertical alignment. Therefore, many of Berger’s double recordings appear rather idiosyncratic and unsatisfactory from a technical point of view, a fact of which he was well aware.
In July, 1924, Berger observed small, tremulous movements of the galvanometer string while recording from the skin overlying a bone defect in a seventeen-year-old patient (who had been a subject for his earlier cortical stimulation experiments and who had been operated on earlier because he was suspected of having a brain tumor). In his first paper on the electroencephalogram, Berger briefly described this case as his first successful recording of an EEG. Nevertheless, from his experimental protocol, it is known that he did not fully trust this observation, although he was greatly encouraged by it. At the time of these early studies, Berger already had used the term “electroencephalogram” in his diary, yet for several years he had doubts about the cerebral origin of the electrical oscillations he recorded. As late as 1928, he almost abandoned his electrical recording studies.
Berger’s first paper on the human encephalogram was published in 1929 as “Über das Elektrenkephalogramm des Menschen” (“On the Electroencephalograph of Man,” 1969) in the Journal für Psychologie und Neurologie, but it had little immediate impact on the scientific world. Indeed, the paper was either ignored or regarded with open disbelief. Even Berger himself was not yet completely free of doubts about the validity of his findings, but he continued his work. He published additional contributions to the study of the electroencephalogram in a series of fourteen papers. As his research progressed, Berger became increasingly confident and convinced of the significance of his discovery.
In his studies on the human encephalogram, Berger repeatedly touched on basic neurophysiological and neuropharmacological problems; he also commented on the characteristics and importance of EEG changes in a variety of pathological states. He approached these questions exclusively from the point of view of his own personal interest in psychophysiology, and it is clear that he was not interested primarily in the basic neurophysiology, neuropharmacology, or clinical pathology of the EEG. Nevertheless, he was the first to make many perceptive observations in these areas and to develop some theoretical concepts about the origin and the regulation of the EEG in normal and pathological states.
There were many reasons for Berger’s lack of immediate recognition and the widespread initial skepticism regarding his work on the EEG of humans. One source of the resistance was to be found among neurophysiologists. Those who conducted research on the axons and their action potentials simply could not believe that regular oscillations of quasi-sinusoidal form could represent the electrical activity of an organ as complex as the human brain and that such activity could be recorded from the scalp.
The situation changed in 1934, when Edgar Douglas Adrian and Brian Harold Cabot Matthews published a paper on the “Berger rhythm.” The two neurophysiologists admitted that, initially, they had been skeptical about the validity of Berger’s work. This skepticism was reinforced by the common assumption that Berger, a psychiatrist, was an unlikely person to make such a striking discovery. However, Adrian, whose competence as a neurophysiologist could not be questioned, fully confirmed Berger’s observations and thus put the seal of scientific respectability on Berger’s work. Soon, interest in the EEG spread throughout all the countries of the Western world—except for Germany. Ironically, soon after the international scientific community finally had accepted Berger into their ranks, he was removed from his post by the Nazis in 1937. Shortly thereafter, his laboratory was dismantled.
The long-range impact of Berger’s work is incontestable. When Berger published his last paper on the human encephalogram in 1938, the new approach to the study of brain function that he inaugurated in 1929 had already gathered momentum in many centers, both in Europe and in the United States. As a result of his pioneering work, a new diagnostic method had been introduced into medicine; physiology had acquired a new investigative tool. Clinical neurophysiology had been liberated from its exclusive dependence on the functional anatomical approach, and electrophysiological exploration of complex functions of the central nervous system in the neurophysiological laboratories had received major impetus. Berger’s work had finally received its well-deserved recognition. Many of those who undertook the study of the electroencephalogram were able to bring a far greater technical knowledge of neurophysiology to bear on the problems of the electrical activity of the brain than Berger was ever able to, yet the community of neurological scientists has not ceased to look with respect to the founder of electroencephalography. Despite overwhelming odds and isolation, Berger initiated a new era of neurophysiology.
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Berger, Hans. “Hans Berger on the EEG of Man.” Translated by Pierre Gloor. Electroencephalography and Clinical Neurophysiology, supp. 28 (1969). An excellent translation of Berger’s fourteen reports (1929 to 1939) on the electroencephalograph of humans. The introduction is the most useful and thorough piece of writing on the history and development of Berger’s work on the EEG. Places Berger’s work in a historical context; provides firsthand documentation on the discovery from Berger’s own diaries. Includes graphs, charts, extensive notes, and an index. -
Cooper, R., et al. EEG Technology. 3d ed. Boston: Butterworths, 1980. In the first chapter, titled “Origins of the Encephalogram,” Berger’s work is cited in its historical context. Although aimed at the EEG technician, the book gives a useful overview of the advances in EEG technology since its inception. Contains appendixes; references follow each chapter. -
Gale, Anthony, and John A. Edwards. Physiological Correlates of Human Behavior. Vol. 2 in Attention and Performance. New York: Academic Press, 1983. A section devoted to the EEG and human behavior describes the pioneers and popularizers of electrical brain-wave recording devices—Caton and Berger in particular. Describes advances in the understanding of brain function from these pioneers to the 1980’s. Contains extensive references and an index. -
Kooi, Kenneth A., et al. Fundamentals of Electroencephalography. 2d ed. New York: Harper & Row, 1978. A compact source of information about human electroencephalography aimed at both the student and technician. Discusses the basic concepts, principles, and clinical information necessary to evaluate EEGs; gives a brief history of the development of the phenomenon. Contains graphs, illustrations, and extensive references after each chapter. -
Nunez, Paul L., and Ramesh Srinivasan. Electric Fields of the Brain: The Neurophysics of EEG. 2d ed. New York: Oxford University Press, 2006. Detailed study of the electrophysiology of the brain, the science of electroencephalography (the recording and analysis of the brain’s electrical activity), and the applications of that science. Bibliographic references and index. -
Scott, Donald. Understanding the EEG. Philadelphia: J. B. Lippincott, 1975. Explains, in simple language, what an EEG is, what diagnostic information it can provide, and what deductions can be made from it. Appeals to those interested in brain activity and its significance—students and practitioners alike. Discusses Berger’s work in a brief historical section. Contains a glossary of terms, bibliography, and an index. -
Zani, Alberto, and Alice Mado Proverbio, eds. The Cognitive Electrophysiology of Mind and Brain. Boston: Academic Press, 2003. An analysis of the relationship between the brain and the mind, using electrophysiological studies of cognitition to bridge the gap. Bibliographic references and index.
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