by Electroencephalography, or EEG, was invented 100 years ago. In the years since the invention of this device to monitor brain electricity, it has had an incredible impact on how scientists study the human brain.
Since its first use, the EEG has shaped researchers’ understanding of cognition, from perception to memory. It was also important in diagnosing and guiding the treatment of multiple brain disorders, including epilepsy.
I am a cognitive neuroscientist who uses EEG to study how people remember past events. The 100th anniversary of the EEG is an opportunity to reflect on the importance of this discovery in neuroscience and medicine.
Discovery of EEG
On July 6, 1924, psychiatrist Hans Berger performed the first EEG recording on a human, a 17-year-old boy undergoing neurosurgery. At the time, Berger and other researchers were making electrical recordings of animal brains.
What set Berger apart was his obsession with finding the physical basis of what he called psychic energy, or mental effort, in humans. Through a series of experiments spanning his early career, Berger measured brain volume and temperature to study changes in mental processes such as intellectual work, attention and desire.
He then switched to recording electrical activity. Although he recorded the first EEG traces in the human brain in 1924, he did not publish the results until 1929. The intervening five years were a torturous phase of self-doubt about the source of the EEG signal in the brain and the experimenter’s refinement. setup. Berger recorded hundreds of EEGs on multiple subjects, including his own children, with both experimental success and difficulties.
Convinced of his results, he published a series of papers in the journal Archiv für Psychiatrie and hoped to win the Nobel Prize. Unfortunately, the research community was skeptical of his findings, and years passed before anyone else began using EEG in their own research.
Berger was eventually nominated for a Nobel Prize in 1940. But no Nobels were awarded in any category that year due to the Second World War and the German occupation of Norway.
Neural oscillations
When many neurons are active at the same time, they produce an electrical signal strong enough to spread instantaneously through the conductive tissue of the brain, skull and scalp. EEG electrodes placed on the head can record these electrical signals.
Since the discovery of EEG, researchers have shown that neural activity oscillates at specific frequencies. In his initial EEG recordings in 1924, Berger observed most oscillatory activity that cycled 8 to 12 times per second, or 8 to 12 hertz, named alpha oscillations. Since the discovery of alpha rhythms, many attempts have been made to understand how and why neurons oscillate.
Neural oscillations are thought to be important for effective communication between specific brain regions. For example, theta cycle oscillations between 4 and 8 hertz are important for communication between brain regions involved in memory encoding and memory retrieval in animals and humans.
Researchers then examined whether they could change neural oscillations and how they would affect how neurons talk to each other. Studies have shown that many behavioral and non-invasive methods can alter neural oscillations and lead to changes in cognitive performance. Performing specific mental activities can trigger neural oscillations in the frequencies used by those mental activities. For example, my team’s research found that mindfulness meditation can increase theta frequency oscillations and improve memory retrieval.
Non-invasive methods of brain stimulation can target frequencies of interest. For example, my team’s ongoing research has found that brain stimulation at an elevated frequency can lead to improved memory retrieval.
EEG has also led to major discoveries about how the brain processes information in many other cognitive areas, including how people perceive the world around them, how they focus their attention, how they communicate through language and how they process emotions.
Diagnosing and treating brain disorders
EEG is commonly used today to diagnose sleep disorders and epilepsy and to guide brain disorder treatments.
Scientists are using EEG to see if non-invasive brain stimulation can improve memory. Although the research is still in its infancy, there are some promising results. For example, one study found that non-invasive brain stimulation at a gamma frequency – 25 hertz – improved memory and neurotransmitter transmission in Alzheimer’s disease.
A new type of non-invasive brain stimulation called temporal interference uses two high frequencies to cause neural activity equal to the difference between the stimulation frequencies. The high frequencies can penetrate the brain better and reach the targeted area. Researchers have recently tested this method in people using 2,000 hertz and 2,005 hertz to send a heated frequency of 5 hertz at the main brain region for memory, the hippocampus. This resulted in improved recall of the name associated with a face.
Although these results are promising, more research is needed to understand the precise role that neural oscillations play in cognition and whether altering them can lead to long-lasting cognitive improvement.
The future of EEG
The 100th anniversary of the EEG gives us an opportunity to reflect on what it has taught us about brain function and what this technique can do in the future.
In a survey commissioned by the journal Nature Human Behaviour, over 500 researchers who use EEG in their work were asked to predict the future of the technique. What will be possible in the next 100 years of EEG?
Some researchers, myself included, predict that we will use EEG to diagnose and create targeted treatments for brain disorders. Others hope that an affordable, widely wearable EEG will be used to improve cognitive function at home or that it will be seamlessly integrated into virtual reality applications. The possibilities are huge.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. It was written by: Erika Nyhus, Bowdoin College
Read more:
Erika Nyhus receives funding from the National Institute of Health, and the National Institute of Mental Health.
