Modulating Gamma Oscillations with Deep Brain Stimulation Improves Motor Symptoms in Parkinson’s Disease
Post by Amanda McFarlan
What's the science?
Deep brain stimulation is a commonly used treatment for improving motor symptoms in individuals with Parkinson’s disease. This treatment consists of stimulating the subthalamic nucleus (nucleus within the basal ganglia that contributes to the control of involuntary movement) via implanted electrodes to help regulate brain activity and improve motor function. It has been shown that deep brain stimulation leads to a reduction in pathologically enhanced beta oscillations in the brain. Additionally, recent findings have suggested that modulations in gamma oscillations may also play a role in the improvement of motor deficits following deep brain stimulation. This week in Brain, Muthuraman and colleagues investigated the effect of deep brain stimulation on resting state oscillatory activity in the brain in individuals with Parkinson’s disease.
How did they do it?
The authors recruited 31 participants who were diagnosed with Parkinson’s disease and had received chronic treatment with deep brain stimulation for 6-12 months prior to the study. For half of the participants, deep brain stimulation was optimal when it was delivered at 130 Hz, while the other half experienced optimal results when deep brain stimulation was delivered at 160 Hz. All participants received a preoperative MRI brain scan and a postoperative CT scan. The authors recorded 10-minute periods of resting state electroencephalography (EEG) activity in four conditions: (1) deep brain stimulation off, (2) deep brain stimulation at clinically effective frequency, (3) deep brain stimulation 20 Hz below the clinically effective frequency, and (4) deep brain stimulation 20 Hz above the clinically effective frequency. The authors performed post-hoc analyses examining beta and gamma frequency bands to determine the effect of deep brain stimulation on oscillatory activity during resting state.
What did they find?
The authors determined that motor impairments were only significantly reduced following clinically effective deep brain stimulation. They found that clinically effective deep brain stimulation also significantly reduced beta power and increased gamma power in cortical regions of the brain that form connections to the basal ganglia. The beta and gamma power for these regions were negatively correlated with one another while the deep brain stimulation was on, but were not significantly correlated when the stimulation was off. Furthermore, the authors observed cross-frequency coupling of gamma oscillations during clinically effective deep brain stimulation in the cortico-basal ganglia brain network. The cross-frequency coupling of gamma oscillations was also shown to be negatively correlated with motor deficits.
What’s the impact?
This study demonstrates that oscillatory activity within the cortico-basal ganglia network is altered following clinically effective deep brain stimulation. The authors showed that alterations in gamma oscillations may play an important role in improving the motor deficits associated with Parkinson’s disease. Together, these findings provide insight into the network-level effects of deep brain stimulation which may be useful in future studies for optimizing treatment for Parkinson’s disease using deep brain stimulation.
Muthuraman et al. Cross-frequency coupling between gamma oscillations and deep brain stimulation in Parkinson’s disease (2020). Access the original scientific publication here.