Can timing brain stimulation suppress Parkinson's beta waves?
Timing electrical pulses to match specific points of a patient's abnormal brain waves can successfully dampen those waves.
Source
Phase-Dependent Suppression of Beta Oscillations in Parkinson's Disease Patients
What they did
Researchers recorded brain activity from eight Parkinson's disease patients during awake brain surgery while delivering low-amplitude electrical stimulation near the subthalamic nucleus. They delivered pulses that drifted naturally across the phases of the patients' abnormal beta-frequency brain waves. They measured how delivering multiple consecutive pulses at specific wave phases affected local brain wave size, neuron firing, and synchronization with the cortex.
What they found
Delivering three to five consecutive electrical pulses at a highly specific, patient-customized phase of the beta wave reduced the wave's amplitude by up to 46.8 percent. This targeted stimulation also decreased the rhythmic firing of nearby populations of neurons by 18.7 percent after four consecutive pulses. Furthermore, suppressing local beta waves weakened the abnormal synchronization between the subthalamic nucleus and the cerebral cortex.
The limits
What it doesn't show
The study did not test whether suppressing these brain waves actually improves patients' physical movement symptoms, as no behavioral tasks were performed. The results are based on a small sample of eight patients under temporary intraoperative conditions that extended their surgery by 15 to 30 minutes, meaning the long-term effects of this stimulation are unknown. Additionally, because the electrical pulses drifted naturally rather than being actively tracked and locked in real-time, the researchers could only observe short bursts of phase-locked stimulation lasting between 50 and 300 milliseconds.
Key terms
- Beta oscillations
- Brain waves in the 15 to 30 Hertz frequency range that are abnormally elevated and synchronized in patients with Parkinson's disease.
- Subthalamic nucleus (STN)
- A small structure in the basal ganglia of the brain that plays a critical role in controlling movement and is a common target for Parkinson's deep brain stimulation therapies.
- Local Field Potential (LFP)
- An electrical signal recorded from extracellular space that represents the summed synaptic activity of a local population of neurons.
- Phase-dependent stimulation
- A technique where electrical pulses are precisely timed to coordinate with a specific point, such as the peak or trough, of an ongoing brain wave.
- Background Unit Activity (BUA)
- A measure of the high-frequency electrical output generated by a population of nearby neurons, distinct from individual single-neuron recordings.
- Corticosubthalamic synchrony
- The degree to which electrical oscillations in the cerebral cortex and the subthalamic nucleus align and coordinate with each other.
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Quiz yourself
In the study, why was one patient excluded because their peak beta frequency differed from the stimulation frequency by more than 5 Hz?
Common questions
Why did the researchers have to target a patient-specific phase instead of using the same phase for everyone?
The optimal phase for suppressing the brain waves varied between patients because of differences in electrode placement, individual brain anatomy, and the unique ways each person's neural circuits reacted to the electrical current.
Did the stimulation change how fast the neurons were firing overall?
No, the low-amplitude stimulation did not change the average firing rate of the neurons, but it did shift when those neurons fired, disrupting their abnormal rhythmic synchronization.
How is this different from standard Deep Brain Stimulation (DBS) used for Parkinson's?
Standard DBS delivers high-frequency electrical pulses continuously without considering the brain's ongoing waves, whereas this experimental method times individual pulses to specific points on the patient's existing brain waves to suppress them more selectively.
How did the researchers remove the massive electrical artifact caused by the stimulation itself?
They used a mathematical algorithm called a Kalman filter to predict and cleanly subtract the electrical stimulation artifact from the recordings without distorting the underlying brain waves.
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