Deep brain stimulation (DBS) can reduce movement problems caused by Parkinson’s disease and new research provides a clearer picture of why the treatment works. Scientists have found that its benefits appear to depend on the stimulation of 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 doctors from the university hospitals of Cologne and Düsseldorf, Harvard Medical School and Charité Berlin. Published in the magazine BrainThe 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.
Identify 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 showed that Parkinson’s disease can be best 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 relieving motor symptoms in people with Parkinson’s disease. The treatment uses implanted electrodes to send small electrical impulses to areas located deep in the brain.
Previous research has provided only part of the picture. Brain imaging studies have helped identify places 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 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 deep brain regions and areas closer to its surface.
Their analysis revealed that the important network connecting the subthalamic nucleus to the frontal areas of the brain largely communicates at a comparatively fast frequency (20-35 Hz). Importantly, the strength of this connection was associated with how much individual patients’ motor symptoms improved after electrode implantation.
A brain rhythm that may shape response to treatment
“These results suggest that a certain brain rhythm acts as a communication channel between the subthalamic nucleus and the cerebral cortex and can mediate the therapeutic effects of deep brain stimulation,” explains Dr. Bahne Bahners, first author of the study, who works at the University Hospital Düsseldorf. “By stimulating the regions that are connected to the identified network, we will likely be able to adjust DBS settings more precisely in the future, especially in patients who have not yet optimally benefited from DBS.”
The findings could therefore provide a basis 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.
The 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.