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fMRI during active GPi DBS uncovers target-specific networks.
Brendan Santyr1, Clement Chow1, Jürgen Germann1,2,3
1Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, ON, Canada.
NPJ Parkinson'S Disease
|July 14, 2026
Summary
Deep-brain stimulation (DBS) for Parkinson's disease modulates brain networks, not just focal regions, improving symptoms. Network changes are linked to specific motor improvements, showing target-dependent effects.
Area of Science:
- Neuroscience
- Neurology
- Medical Imaging
Background:
- Deep-brain stimulation (DBS) is a key treatment for Parkinson's disease (PD).
- Understanding how DBS affects brain activity and networks is crucial for optimizing treatment strategies and target selection.
- Previous research has focused on focal effects, but network-level changes are increasingly recognized.
Purpose of the Study:
- To investigate the network-level effects of active DBS in the subthalamic nucleus (STN) and globus pallidus internus (GPi) in Parkinson's disease patients.
- To correlate brain network modulation with clinical improvements in motor and cognitive symptoms.
- To explore target-specific differences in network engagement and their impact on outcomes.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to study brain activity in 36 PD patients during active DBS.
- Patients underwent DBS targeting either the STN or GPi.
- Network modeling was employed to analyze functional connectivity and its relationship with clinical symptom severity.
Main Results:
- Active DBS induced widespread cortical modulation associated with clinical improvement at the group level.
- Somatomotor network modulation was significantly linked to gait improvement (p<0.03) and bradykinesia improvement (p<0.06).
- Unexpectedly, somatomotor network modulation showed a nominal association with verbal fluency (p<0.08), while language and cognitive networks had minimal impact. STN-DBS did not show similar verbal fluency associations.
Conclusions:
- DBS therapeutic effects in Parkinson's disease are best understood as the modulation of distributed brain functional networks, rather than isolated focal regions.
- The findings highlight symptom-specific network coupling, with somatomotor network engagement being crucial for motor improvements.
- Target-dependent network modulation may explain differential cognitive and motor outcomes observed with STN-DBS versus GPi-DBS.
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