We’ve got your signal!
One day in 1893, the young 19-year-old Hans Berger, who later became the famous German psychiatrist, took a life-threatening fall from his horse during a maneuver in military service. On that same day, his sister got a very bad feeling, being worried about her brother and she insisted that her father would send a telegram to ask how Hans was doing. Hans Berger interpreted this incidence as a case of telepathy and decided to research how thoughts could be transferred between people. He returned to Jena and studied medicine to investigate the relationship between objective activity in the brain and subjective mental phenomena. In 1924, he eventually became the first person in 1924 to succeed in measuring the electrical activity of the human brain on the surface of the scalp, which he called electroencephalography (EEG). These key contributions have since been considered “… the most surprising, remarkable, and momentous developments in the history of clinical neurology” (Millet and Davids, 2002).
The ‘tower’ shown in the picture is one of the first generation EEG registration systems of the UG.
A collection of historical EEG devices can be seen in the basement of the Heymans Institute at the University of Groningen (UG), in the research laboratories of the Department of Psychology. One of the most striking devices is a huge EEG registration ‘tower’ from the 1970s, which you can see in the featured image. In the 1970’s, there were no companies producing such devices for research. If researchers wanted to conduct EEG research or use it for clinical purposes, a device had to be tailor made by the research support department. The ‘tower’ shown in the picture is one of the first generation EEG registration systems of the UG, developed by Joop Clots, one of the founding fathers of research devices at the Heymans Institute.
In the 1970’s, the individual psychology departments were still spread throughout the city of Groningen. Clinical neuropsychology, for example, was located in the department of neurology, experimental clinical psychology was on the grounds of medicine, and biological psychology was located at the biological center in Haren (near the Botanical Gardens). This was all before these departments were united with pedagogics and social sciences in 1990 to form the present Faculty of Behavioural and Social Sciences (BSS).
1000 sheets of paper were needed for one hour of EEG measurements.
Back then, the recorded EEG signal was still written on continuous paper, similar to the classic seismographs and Hollywood lie detectors. Jan Stalman, the former facility manager of BSS, remembers how EEG researchers came out of the labs with their pockets full: 1000 sheets of paper were needed for one hour of EEG measurements. It was a technical masterpiece to bring the EEG down on paper at all, because the brain signals measured at the scalp have a potential of only 5 to 100 µV (1 µV or microvolt = 1 millionth of a volt). For comparison: a normal AAA battery already supplies 1.5 volts, about ten thousand times more. To make brain activity visible, one therefore needs a sensitive measurement amplifier that ‘magnifies’ the physical signals. You can imagine this like a microphone that makes your voice louder.
“We have got your signal” is more than just a slogan.
A major challenge for the developers of EEG amplifiers is that brain activity is not selectively amplified, but all possible measured signals are amplified at once, including unwanted artefacts. Without suppression of artifacts, such as the ubiquitous background electrical activity like a computer in the room, cables in the wall or a vacuum cleaner next door, these are disproportionately emphasized and would mask the brain activity. Leo van Eykeren found a solution that was called the “average reference”, another innovative invention that contributed to the foundation of the Dutch company TMSi and is now found in EEG devices. TMSi’s current slogan “We have got your signal” is therefore more than just a slogan, it also acknowledges the achievement of the engineers and EEG developers. Their devices are in use in psychology labs and continue to inspire research at the Heymans Institute.
Acknowledgement: This article is the English version of a Dutch contribution to the Groningen University Museum’s book on museum objects, which will be published in 2023. Much of the information is derived from stimulating conversations and email correspondence with Mark Span, Jaap Bos, Jan Stalman and Joop Clots for whose willingness to provide information I would like to express my sincere thanks.
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Millet, David (2002). “The Origins of EEG”. International Society for the History of the Neurosciences (ISHN).
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Featured image taken by Ciska Ackermann.