Deep brain stimulation (DBS) can reduce movement problems caused by Parkinson’s disease, and new research is providing a clearer picture of why the treatment works. Scientists have found that its benefits appear to depend on stimulating a specific brain network that communicates primarily through a relatively fast beta rhythm (20 to 35 Hz).
The findings come from an interdisciplinary group of neuroscientists and clinicians at the University Hospitals of Cologne and Düsseldorf, Harvard Medical School and Charité Berlin. Published in the journal Brain, the study, ‘The Deep Brain Stimulation Response Network in Parkinson’s Disease Operates in the High Beta Band’, is the first to bring together two approaches that have largely been studied separately: electrophysiology and brain imaging.
Pinpointing Where and How Brain Stimulation Works
“For the first time, we were able to characterize the DBS response network in Parkinson’s disease in terms of space and time, simultaneously,” says Professor Dr. Andreas Horn from the University of Cologne, who led the study and specializes in computational neurology. “We show that Parkinson’s disease can best be treated if we stimulate a very precisely defined network. This network operates synchronized within a specific frequency band, and offers an explanation for how well patients respond to deep brain stimulation.”
Deep brain stimulation of the subthalamic nucleus is already an established therapy for easing motor symptoms in people with Parkinson’s disease. The treatment uses implanted electrodes to deliver small electrical pulses to areas located deep inside the brain.
Previous research has provided only part of the picture. Brain imaging studies have helped identify the locations where stimulation appears to work most effectively, while electrophysiological research has measured the frequencies of the electrical signals involved. Until now, researchers had not captured both the spatial location and timing of these signals at the same time.
Mapping a Parkinson’s Brain Network
To investigate this connection, the team studied a large multicenter group consisting of fifty patients and one hundred brain hemispheres. The scientists simultaneously recorded brain activity through the implanted DBS electrodes and with magnetoencephalography (MEG).
Using these recordings, they mapped functional connections between regions deep within the brain and areas closer to its surface.
Their analysis revealed that the important network connecting the subthalamic nucleus with frontal areas of the brain communicates largely at a comparatively fast frequency (20-35 Hz). Importantly, the strength of this connection was associated with how much individual patients’ motor symptoms improved following electrode implantation.
A Brain Rhythm That May Shape Treatment Response
“These results suggest that a certain rhythm of the brain acts as a communication channel between the subthalamic nucleus and the cerebral cortex and may mediate the therapeutic effects of deep brain stimulation,” explains Dr. Bahne Bahners, first author of the study, who works at Düsseldorf University Hospital. “By stimulating regions that are connected to the identified network, we will probably be able to adjust DBS settings more precisely in the future, especially in patients who have not yet benefited optimally from deep brain stimulation.”
The findings could therefore provide a foundation for making deep brain stimulation more precisely tailored to an individual patient’s brain network, particularly when existing DBS settings do not provide the desired level of symptom relief.
Researchers now plan to investigate more directly how deep brain stimulation causes changes within brain networks. Studies examining these causal effects are currently underway.
The study was largely funded by the Professor Klaus Thiemann Foundation.