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.


Arns, M., & Sterman, M. B. (2019). Neurofeedback: How it all started. Brainclinics Insights.

Coenen, Anton; Edward Fine; Oksana Zayachkivska (2014). “Adolf Beck: A Forgotten Pioneer In Electroencephalography”. Journal of the History of the Neurosciences. 23 (3):276-286.

Millet, David (2002). “The Origins of EEG”. International Society for the History of the Neurosciences (ISHN).

Wellach, I. (2015). Praxisbuch EEG. Grundlagen, Befundung, Beurteilung und differenzialdiagnostische Abgrenzung. Akt Neurol, 42, 155.

Picture credits:

Featured image taken by Ciska Ackermann.

Stefanie Enriquez-Geppert is an Assistant Professor at the Department of Clinical and Developmental Neuropsychology at the University of Groningen. Her research focuses on executive dys-/functions. The scope of her examination is the specification of neurocognitive processes underlying executive dys-/functions in young and elderly participants, and in particular in patients with impaired executive control (e.g., schizophrenia, obesity, and brain lesions). She develops and applies neuroscientific approaches (including neurofeedback and behavioural computerized training) to enhance executive functions. Stefanie Enriquez-Geppert studied at the University of Münster, Germany and graduated with an emphasis on cognitive neurosciences in 2007. After her psychology studies she worked on a Phd project about “Inhibition and conflict monitoring as assessed with EEG, structural and functional MRI” at the University of Münster, Germany and finished her PhD in the year 2010. After that she did a postdoc at the University of Oldenburg (Germany) with a focus on neural oscillations and a second postdoc at the University of the Balearic Islands in Spain. She spent several research stays abroad, for instance at the University of Mexico in Yucatan, at the University of Bergen, Norway, and the MRC in Cambridge, UK. For further information visit: http://www.enriquez-geppert.com.

Selected publications:

Garcia Pimenta M., Brown T, Arns M, Enriquez-Geppert, S. (2021). Treatment Efficacy and Clinical Effectiveness of EEG Neurofeedback as a Personalized and Multimodal Treatment in ADHD: A Critical Review, Neuropsychiatr Dis Treat

Ros, T.*, Enriquez-Geppert, S.*, Zotev, V., Young, K. Wood, G., Whitfield-Gabrieli, S., Vuilleumier, P., et al. (2020). Consensus on the reporting and experimental design of clinical and cognitive-behavioural neurofeedback studies (CRED-nf checklist). Brain. (* shared first authorship)

Enriquez-Geppert, S., Flores-Vázquez, J.F., Lietz, M ., Garcia-Pimenta, M ., Andrés, P . (2020). I know your face but can’t remember your name: Age-related differences in the FNAME-12NL. Archives of Clinical Neuropsychology, acaa107, https://doi.org/10.1093/arclin/acaa107

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  • Stephan Schleim January 13, 2023  

    Interesting. Thanks. I think Berger called it “psy energy” that he wanted to measure in the brain. It’s also a nice example that even wrong ideas can eventually lead to scientific progress in the long run.

  • Stephan Schleim January 13, 2023  

    That’s, by the way, how a German newspaper wrote about Berger’s breakthrough in 1930:

    “Today they are still secret signs, tomorrow one may perhaps detect mental and brain disorders in them and the day after tomorrow people may even write each other letters in brain writing.” (Stadt-Anzeiger Düsseldorf 6.8.1930 quoted from Cornelius Borck, 2005. Hirnströme, p. 7.; my transl.)

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