Researchers have discovered that irregular brain signals, previously dismissed as ‘noise’, track Parkinson’s symptoms more accurately than traditional markers.
The finding could help improve deep brain stimulation (DBS), a treatment that uses mild electrical pulses to ease symptoms by modulating abnormal brain activity.
Scientists at the Max Planck Institute in Germany, working with teams from two other German universities and two in the UK, analysed brain recordings from 119 people with Parkinson’s who had undergone DBS surgery at five European hospitals.
The patients had a mean age of 63 and had lived with the disease for almost 10 years on average. Motor tests showed moderate to severe impairment.
For years, scientists have focused on rhythmic brain waves called beta waves, repeated electrical patterns that occur when groups of nerve cells fire together in a coordinated way.
In Parkinson’s, these beta waves become unusually strong and have been linked to symptom severity.
However, when the team examined these rhythmic waves, they found the link to symptoms was weaker than expected.
“We wondered why earlier studies from different centres had produced such mixed results,” said Vadim Nikulin, principal investigator at the Max Planck Institute.
“Did the patient groups differ, the recording equipment, or the analysis methods?”
The researchers then analysed the brain’s background electrical activity, irregular signals often dismissed as ‘noise’.
Unlike the neatly repeated beta patterns, this noise reflects more uncoordinated firing of different nerve cells.
By separating the rhythmic from the non-rhythmic components, they found this irregular signal tracked patients’ motor symptoms much more closely than beta waves.
“You can imagine the brain as a concert hall full of musicians before a rehearsal,” said Moritz Gerster, a doctoral student at the Max Planck Institute who led the study.
“Some groups play together, creating a distinct rhythm. Others practise on their own, merging into a non-rhythmic ‘noise’.
“If you only measure the overall volume, you miss this distinction.”
Because Parkinson’s affects each person differently and DBS is only used in advanced disease, the study had no healthy control group.
Instead, the team used the fact that Parkinson’s typically affects one side of the body more than the other.
“That gave us the idea to compare the more affected hemisphere with the less affected one,” Gerster said.
“This way, each patient could practically serve as their own control.”
The hemisphere controlling the more affected side showed much higher levels of irregular activity, suggesting an increased firing rate of nerve cells.
The team said this non-rhythmic signal could serve as a biomarker, a kind of personal electrical fingerprint that tracks symptom severity over time.
The newly identified electrical signature may help make DBS more precise.
Instead of delivering continuous stimulation, adaptive electrodes already available could monitor brain activity in real time and apply stimulation only when needed, the researchers said.
