Hans Berger lecturing at the University of Jena during the 1920s
From: Millett, 2001
The invention of the electroencephalogram (EEG; from the Greek and Latin electro- + encephalo- (“brain”) + -gram (“recording”)) is one of the key milestones in the history of neurology. It virtually paved the path for modern-era research on human brain physiology. The EEG is a method for recording of brain-generated electrical signals picked up from the scalp. Spontaneous electrical rhythms of the mammalian brain were first captured back in the 1870s by Russian physiologist Vasili. Y. Danilevsky and British physician Richard Caton, independently of each other1,2. While the first EEG of the mammalian (dog) was obtained in 1921 by Vladimir. V. Pravdich-Neminsky, a physiologist from Russia, the recording of the first human EEG tracings, as well as the very term “EEG”, is credited to the the German psychiatrist Hans Berger1-7.
Hans Berger was born to the family of physician Paul Friedrich Berger on May 21, 1873, in the town of Neuses (Germany).1,4 His maternal grandfather was the famous poet Friedrich Rückert, from whose poems Hans drew inspiration throughout his life1.
At first, Berger did not take much interest in a medical career – he favored mathematics and astronomy, and even pursued these sciences at the University of Berlin. However, life in Berlin turned out too difficult for 19-year-old Berger, and he left university for military service1. One odd incident that occurred during that time had a profound impact on the rest of his life1,7. He fell off his horse right in the path of an artillery cart, which luckily stalled at the last minute, leaving him unharmed1. Later in the evening, he received a telegram sent by his father at the insistence of Hans’s elder sister. On the morning of the incident, she had a feeling that something terrible had happened to her brother. Berger, who had never received telegrams from his family before, was amazed at that coincidence and thought that he and his sister had experienced a telepathic contact1. Probably, it was largely under the influence of that incident that Berger abandoned the career of an astronomer and became involved in medicine and psychophysiology, devoting himself to a search for a link between brain activity and psychical processes1,4.
After the completion of his military service, Berger studied medicine in Berlin, Würzburg, Kiel, and Jena4. In 1897, he obtained his medical degree from the University of Jena and became assistant to the well-known psychiatrist Otto Ludwig Binswanger at the university’s psychiatric clinic1,4,5. Berger worked at the University of Jena all his life and through the entire course of his academic career, eventually becoming professor and succeeding Binswanger to the office of Director of the clinic in 1919,1,4 which he held until his retirement in 19384,5. In addition to his research and administrative activities, Berger delivered lectures on neuroanatomy, neurophysiology, and general and forensic psychiatry, and even served as a German Army doctor during World War I6.
His first investigations, led by Binswanger, were conventional, but in the late 1890s, Berger was already carrying out a novel series of clinical experiments that ultimately led to the development of the human EEG. He sought the physical bases of parapsychological phenomena, aspiring to disclose the mysterious relationship between matter (brain) and thought (mind) 1,3. At that time, the scientific principle of energy conservation, which became full-fledged in the 19th century, prevailed not only among physicists but also among physiologists.1 The latter would commonly use it in their endeavors to create an “energetic” model of brain function – the one representing the mind-brain interaction.
Berger’s attention was thus attracted by Alfred Lehmann’s postulations that the physical equivalent of feelings, emotions and mental work can be determined through precise measurement of all the components of cerebral energy. According to Lehmann, energy emanating in the brain via chemical processes (metabolism) can convert into three major forms: heat, electricity and psychic energy. Based on the principle of energy conservation, Lehmann believed it was possible to calculate the energy that has transformed into thoughts, feelings and emotions, i.e. psychic energy, by estimating metabolic energy and precisely measuring the heat and electricity generated by the brain1,3. Berger adopted this model of brain function, setting out to measure metabolic energy and its conversion into heat, electricity and mental phenomena. He believed that careful measurements of cerebral energetics would help in acquiring evidence of extrasensory phenomena, such as telepathy.1
Berger started with recording changes in cerebral blood flow, the most obvious measure of the energy supply driven to the brain. Of course, there were no analogs of today’s cerebral blood flow imaging techniques at that time, so Berger took advantage of his official position. He performed direct measurements of the pulsations of cerebral blood flow in patients with cranial defects while they were delivered a variety of sensory stimuli or asked to perform various mental tasks. However, after 8 years of experimentation, Berger became disappointed in that kind of approach1,7 and, instead of measuring energy supply to the brain, he decided to turn his attention to measuring the energy converted into heat and electricity during various mental tasks. He believed that by measuring cerebral energy converted into heat and electricity, it was possible to theoretically calculate the energy transformed into psychical activities, and possibly even mental telepathy1. Berger was convinced that human thought bore physical properties and could be transmitted from person to person.
At first, he began investigating changes in heat emitted by the brain1,4. Relying on his own thermometric records, previous calculations of weight, volume and heat capacity of the cerebral cortex and approximate estimates of heat and mechanical work produced by muscle cells, Berger calculated the maximum amount of energy that could be transformed into mental activity1. The meticulous scientist was yet unsatisfied. The analysis of psychic energy was still incomplete without investigation of electricity produced by the brain.
In his earliest experiments, he tried to record electrical signals of the dog brain1,4. However, after World War I, he focused on developing a method of recording the electrical activity of the human brain. He designed his own original device for his project. The first “Berger’s machine” was a single-channel recorder used to trace the brain’s bioelectrical activity. Recordings were captured with an oscilloscope on photographic paper, which was then developed1,2. In his experiments, Berger was constantly facing significant technical obstacles – apparatuses of that time were far from perfection. He was working almost alone in his continuous pursuit to improve the biopotential recording technique1. It is worthwhile noting that while at the beginning of his work, Berger was supported by his colleagues and university management, at later points, probably due to his withdrawn disposition and critical attitude of fellow researchers (his recordings were considered artifacts), he became increasingly isolated in his efforts1,2.
Constant technical pitfalls only aggravated the researcher’s self-criticism and episodes of depression. Nevertheless, his perseverance and belief in own ideas eventually rendered his attempts to record the electric activity of the brain successful. After more than 20 years of strenuous work, Hans Berger managed to record the brain’s electrical potentials, using a small Edelman galvanometer, directly from the cortical surface of the brain of a 17-year-old youth, who had undergone surgery for the removal of a brain tumor1,4. Berger’s diaries reveal the exact date he succeeded in obtaining consistent EEG recordings – July 6, 19241-7. He wrote down: “It is possible that I might fulfill the plan I have cherished for over 20 years and even still, to create a kind of brain mirror: the Elektrenkephalogramm1!”
In subsequent years, Berger worked hard attempting to improve the “brain wave” recording technique. Gradually, he was able to record such waves not only from the brain of patients with skull defects but also from the scalp of healthy individuals (including himself and his son Klaus) 1,4. Initially, recordings were performed with the use of needle electrodes, which were inserted underneath the scalp1,2. Later Berger refined the method and carried out recordings from the surface of the scalp using lead, zinc, or platinum electrodes, with a silver spoon placed in the patient’s mouth serving as a reference (“zero” point with reference to which the magnitude of a potential is measured by recording electrodes) 1,2. Berger managed to obtain high-quality EEG tracings, which displayed distinct varied waveforms, which changed with the state of the subject1. This instilled even greater confidence in Berger that his “bran mirror”, EEG, would ultimately be able to reflect mental activity.
One of the earliest high-quality EEG tracings recorded by Berger in 1928–1929. The lower curve is an ECG and the upper one is an EEG tracing depicting bursts of alpha waves appearing as the subject lies with his eyes closed in a state of mental and physical rest.
From: Millet, 2001
In the spring of 1929, almost 5 years after recording the first human EEG, he finally cast away his doubts and published his findings in a research paper titled “On the Human Electroencephalogram” 8. Over the following decade, he published 13 more similarly titled papers on this subject – only numbered differently (1-14) 1,7. Overall, Berger published 23 scientific papers addressing human EEG tracings2,5, and in 1938 he released a monograph which summarized these studies9. In his works, Berger described normal and pathological EEGs, as well as EEG changes correlated with man’s state. In this regard, he singled out two main types of activity: sinusoidal waves of about 10 Hz, which Berger named “alpha rhythm”, and higher-frequency waves, “beta rhythm”. Alpha rhythm occurred when the patient’s eyes were closed, and was replaced by beta activity with eye opening or sensory stimulation1,2,4,7. The pattern of “brain waves» changed with mental exertion or in states such as sleep, general anesthesia or hypoxia. Berger showed that the EEG differs in infants, the elderly, patients with epilepsy, tumors or cerebral lesions, or “flattens out” (activity disappears) following death1,2,4,7.
Despite Berger’s extremely careful and thorough approach to experiments, his work originally met with skepticism and doubt or would simply be disregarded by the medical community2,4. It was not before Berger’s works were corroborated and endorsed in 1934 by Lord Edgar Douglas Adrian, the Nobel Laureate in Physiology or Medicine and a highly reputable physiologist, that the EEG method began to gain international recognition1,4,7. Together with Lord Adrian, Berger presided over the International Congress of Psychology in Paris (1937), where he was greeted with much honour2,4,7. However, his works never received the same degree of acclaim in Germany.
The changes unfolding in the country (takeover of power by the Nazi Party), uneasy relationships with colleagues and authorities (Berger did not join the party, unlike most of his university colleagues, but he was forced to be a member of an affiliated group, perhaps for the sake of self-protection6), as well as retiring (on reaching 65 years of age) as Professor of Psychiatry and Director of the psychiatric clinic at Jena in 1938 drained Berger’s health and worsened his episodes of depression. He was unable to continue his research1,2,4. As a consequence, the scientist hung himself at the university’s clinic on June 1, 9411-7, without having even a slightest idea that he had been nominated three times for the Nobel Prize a year earlier7,10. Later Hans Berger was nominated three more times for the prize, posthumously, though (in 1942, 1947 and 1950)10, for which reason his nominations could not be considered (the rules allow the prize to be only won during a lifetime).
Although it has been nearly a century since the first human EEG was recorded, this technology is still of value in diagnostics of numerous diseases of the brain. Working like a “brain seismometer”, it is the only method with extremely high temporal resolution, which is capable of real-time capturing changes going on in the brain during, for example, an epileptic seizure. Although Berger never identified the physical bases of mental activity and telepathy, some of the ideas he postulated acquired particular relevance at the end of the 20th century, with the development of the brain-computer interface. Of course, we are not yet capable of mind reading, but, with the help of the EEG, some objects can already be “thought powered” today11.
1. Millett D. (2001). Hans Berger: from psychic energy to the EEG. Perspect Biol Med. 44(4): 522-42.
2. Aleksandrov M.V. (2012). The history of electroencephalography: a Russian overture to the world’s symphony (to the 100th anniversary of V.V. Pravdich-Neminsky’s works). Physiol. 13 (2): 372–384.
3. Millet D. (2002). The Origins of EEG. International Society for the History of the Neurosciences.
4. Karbowski, K. (2002). Hans Berger (1873-1941). Journal of Neurology, 249(8), 1130–1131.
5. Haas LF. (2003) Hans Berger (1873–1941), Richard Caton (1842–1926), and electroencephalography. Journal of Neurology, Neurosurgery & Psychiatry. 74: 9.
6. Zeidman, L. A., Stone, J., & Kondziella, D. (2013). New Revelations About Hans Berger, Father of the Electroencephalogram (EEG), and His Ties to the Third Reich. Journal of Child Neurology, 29(7), 1002–1010.
7. Kaplan, R. M. (2011). The Mind Reader: the Forgotten Life of Hans Berger, Discoverer of the EEG. Australasian Psychiatry. 19 (2): 168–169.
8. Berger H. (1929). Über das Elektroenkephalogramm des Menschen [On the use of the encephalogram in humans]. Arch Psychiatr Nervenkr. 87: 527-570.
9. Berger H. (1938). Das Elektrenkephalogramm des Menschen [Electroencephalogram of the human]. Nova Acta Leopoldina, Halle (Saale). 6: 173-309.