A gentle method to unlock the mysteries of the deep brain

An established and truly non-invasive analysis technique.

The electroencephalogram records the electrical activity of the brain in a non-invasive way using 256 electrodes placed on the scalp. Thanks to mathematical algorithms combined with anatomical imaging, we can see what is happening in the deepest part of our brain, without having to enter it directly. © UNIGE
The electroencephalogram records the electrical activity of the brain in a non-invasive way using 256 electrodes placed on the scalp. Thanks to mathematical algorithms combined with anatomical imaging, we can see what is happening in the deepest part of our brain, without having to enter it directly. © UNIGE

The Subcortex regions of the brain are located below the cerebral cortex and completely covered by it. As they are located in the deepest reaches, the feasibility to detect subcortical signals is a matter of debate. Scientists do know the critical role the regions play in motor, emotional and associative activity, but they do not exactly know their functions.

Existing treatments for regulating and measuring the activity of the subcortical areas are highly invasive, and sometimes work without us really knowing how.

Now, scientists at the University of Geneva Switzerland in collaboration with Cologne University (Germany) have investigated whether a non-invasive method – electroencephalography (EEG) – could be employed in tandem with mathematical algorithms to measure this brain activity externally.

For the first time, they proved that this technique is able to record signals usually only seen by implanting electrodes in the brain.

Using the technique, scientists were able to quantify and record the electrical activity of the subcortical areas of four OCD and Tourette’s patients who had been given electrode implants. While doing this, patients were equipped with an EEG as the scientists measured the activity of the same areas from the surface.

Scientists also developed mathematical algorithms to precisely interpret the data provided by the EEG and ascertain where the brain activity was coming from. The outcomes they received correlated perfectly.

Christoph Michel, a professor in the Department of Basic Neurosciences in UNIGE’s Faculty of Medicine said, “In obtaining highly similar signals as with the implants, we finally proved that surface EEG can be used to see what is happening in the deepest part of the brain without having to go into it directly!”

Martin Seeber, a researcher in the Department of Basic Neurosciences and the study’s first author. said, “Current treatments, based on deep brain stimulation are highly invasive: implanting electrodes into the center of the brain, which is stimulated electrically by an external stimulator. Although this technique has been shown to be effective in Parkinson’s, unfortunately, it doesn’t work so well for OCD and Tourette syndrome.”

Michel said, “To improve existing treatments, it has become essential to understand how these subcortical zones function and how they communicate. Since implanting electrodes is an extremely invasive technique, another method was called for to increase the number of subjects studied.”

“We naturally thought of EEG, which records the electrical activity of the brain using 256 electrodes placed on the scalp. But is it really possible to measure deep brain activity from outside the skull?”

“Lastly, we hope that in time we’ll be able to stimulate the deep brain areas from the surface via an electromagnetic treatment, doing away with electrode implants in the brain once and for all!”

Seeber said, “Now that we know that EEG can be used to analyze the subcortical zones. We can try to understand how they communicate with each other and the cortex in the hope that we’ll be able to better understand the causes of diseases such as Tourette’s and OCD.”

Scientists are further planning to use the technique to improve current treatment methods, based on rebalancing network interactions using a very slight electric shock. They would also like to apply them to other diseases such as obesity, addiction or Alzheimer’s.

The results are published in Nature Communications.