A study by the University of Oldenburg shows that individual anatomical differences play a major role in how electrical brain stimulation works. The finding could benefit patients of schizophrenia or ADHD.
Electrical brain stimulation (EBS) is considered a promising method for treating neurological and psychiatric diseases, but also for better understanding the way the brain works. An Oldenburg University (Germany) research team led by the psychologists Prof. Dr. Christoph Herrmann and Dr. Florian Kasten has now found how the effects of EBS can be better predicted in individuals. "The result is a milestone to add on the way to future therapeutic applications of the method," says Prof. Dr. Herrmann, who heads the Department of General Psychology at the University of Oldenburg. The researchers presented their study in the journal Nature Communications.
EBS is designed to either stimulate nerve cells in specific areas of the brain to increase their activity or to inhibit their activity. For this purpose, electrodes are attached to the scalp. They generate weak direct or alternating electrical currents. Transcranial Alternating Current Stimulation (tACS) can be used to influence the strength and frequency of electrical brain activity. The treatment usually aims to normalize the activity of diseased brain regions. "Up until now, however, the effects of brain stimulation have usually been relatively weak and highly variable," said Dr. Kasten. The effectiveness of the procedure had been therefore generally questionable.
The team led by Prof. Dr. Herrmann and Dr. Kasten has now investigated the influence of individual anatomical differences on the effect of EBS. To this end, they first produced structural images of the brain from 40 test persons using the university's magnetic resonance tomography. This enabled them to calculate current flows through the brain for each participant. They also produced maps of the brain activity of these persons using magnetoencephalography (MEG).
Twenty participants received a twenty-minute brain stimulation, twenty others received only a sham treatment. The team found that the brain stimulation had a strong effect when the calculated map of current flow in the brain and the map of brain activity were very similar in one subject. If there are fewer overlaps between the two, the brain stimulation has a correspondingly weaker effect. The results now allow researchers to predict the effects of brain stimulation in a more accurate way than it had been achieved until the study.
Florian Kasten, Katharina Duecker, Marike Maack, Arnd Meiser & Christoph Herrmann: "Integrating electric field modeling and neuroimaging to explain inter-individual variability of tACS effects", Nature Communications 10, 5427 (2019), doi.org/10.1038/s41467-019-13417-6