Less active brain waves may signal cognitive decline in Parkinson’s

Findings could lead to novel targeted therapies, biomarkers of cognitive function

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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People with Parkinson’s disease who are experiencing cognitive decline may show weaker low-frequency brain waves on an electroencephalogram (EEG), a recording of the brain’s electrical activity, according to a recent study.

Brain waves recorded at the front part of the brain were linked to measures of cognitive decline and executive function impairment.

“Our work provides insight into fundamental mechanisms of [Parkinson’s disease]-related cognitive dysfunction and could lead to novel targeted therapies and neurophysiological biomarkers for cognitive symptoms of [Parkinson’s disease],” researchers wrote.

The study, “Evoked mid-frontal activity predicts cognitive dysfunction in Parkinson’s disease,” was published in the Journal of Neurology, Neurosurgery and Psychiatry.

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Up to 80% of Parkinson’s patients will have cognitive problems

Parkinson’s occurs due to a loss of nerve cells in the brain, and its symptoms usually develop slowly over many years. While the disease is best known for its motor symptoms, there are also non-motor symptoms, which may range from mood changes to cognitive decline, including trouble with memory and thinking.

“Cognitive decline, including dementia, is a significant and underappreciated symptom of Parkinson’s disease. Around 30% of patients can have cognitive symptoms at the beginning of the disease, and up to 80% will have cognitive problems at some point in their disease,” Nandakumar Narayanan, MD, PhD, an associate professor of neurology at the University of Iowa and the study’s senior author, said in a university press release.

“Furthermore, although we have quite a few effective treatments for the motor symptoms of Parkinson’s, including medical therapies and deep brain stimulation, we have very few treatments for the cognitive aspects of Parkinson’s disease,” Narayanan said.

What exactly causes cognitive decline in Parkinson’s is unclear, but it’s possible that patterns of brain activity in the front part of the brain, which is home to areas involved in cognitive thinking, may be disrupted in people with the disease.

Cognitive decline, including dementia, is a significant and underappreciated symptom of Parkinson’s disease.

EEG is widely available, non-invasive way to record brain electrical activity

To test this idea, a team of researchers led by Narayanan used EEG, a widely available, non-invasive, and inexpensive method of recording the brain’s electrical activity, in a large group of Parkinson’s patients with different levels of cognitive function impairments.

“Traditional methods for diagnosing cognitive problems often involve time-consuming pen and paper tests … In addition, because these traditional tests can be ‘learned,’ they cannot be used repeatedly over time for the same patient,” Narayanan said. “In contrast, EEG can be done continuously over several hours or days. It can be applied in nursing homes, or patient’s homes, and it gives you a richly featured description of a patient’s cognitive status.”

The study included a total of 100 people with Parkinson’s, including 47 without cognitive impairments, 34 with mild cognitive impairment, and 19 with dementia, and 49 control individuals who were about the same age and had similar demographic features. All were asked to complete three different tasks to test how well they stayed focused, processed information, or made decisions.

The researchers wanted to see if patterns of brain activity could signal cognitive decline, and focused on two types of low-frequency electrical impulses, or brain waves, known as delta (1-4 Hz) and theta (4-7 Hz) waves. These brain waves were recorded by placing a single EEG electrode on the scalp at the front part of the brain while patients were performing the tasks.

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Patients with cognitive problems showed slower response times

People with Parkinson’s who were experiencing cognitive problems showed slower response times and lower-power delta waves across all tasks. This finding suggests that their brain may respond differently to these cues.

“The effect was seen simply because the patient was required to pay attention to a cue and respond. I think this is the deep insight into why Parkinson’s patients have cognitive problems: they fail to engage these basic response processes in the brain,” Narayanan said.

“That was very surprising to us, and it’s helpful because it means we might be able to get information about cognitive function using the simplest version of this task where there’s a cue, and the patient has to engage and respond,” he said.

The researchers also found that EEG data gathered via a single electrode was strongly correlated with the Montreal Cognitive Assessment score, a measure of cognitive function, and the National Institutes of Health Toolbox Executive Function score, which evaluates skills like self-control, planning, and decision-making.

“Our results provide insight into the nature of low-frequency frontal rhythms and suggest that [Parkinson’s disease]-related cognitive dysfunction results from decreased delta/theta activity,” the researchers wrote. “These findings could facilitate the development of new biomarkers and targeted therapies for cognitive symptoms of [Parkinson’s disease].”