Summary: Data from a single EEG electrode might predict cognitive decline, including dementia, in patients with Parkinson’s disease.

Researchers discovered that reduced strength of specific low-frequency brain waves, known as delta and theta waves, was strongly linked to cognitive dysfunction in these patients. The non-invasive and inexpensive nature of EEG makes it a potential tool for diagnosing cognitive impairment in Parkinson’s patients.

The findings also suggest the EEG measurements might help monitor and adjust cognitive side effects of Parkinson’s treatments.

Key Facts:

1. Cognitive decline is a significant symptom in Parkinson’s disease, with up to 80% of patients experiencing cognitive problems at some point in their disease progression.
2. The EEG data suggests a strong link between diminished strength of delta and theta brain waves during cognitive engagement and cognitive dysfunction in Parkinson’s patients.
3. The EEG measurements may provide a cost-effective, non-invasive way to monitor cognitive side effects of Parkinson’s treatments, and potentially to determine the effectiveness of new treatments.

Source: University of Iowa

A few minutes of data recorded from a single electrode placed on top of the head may be sufficient to predict thinking problems, including dementia, in patients with Parkinson’s disease (PD).

The finding from a new University of Iowa study might help improve diagnosis of cognitive disability in PD and develop new biomarkers and targeted therapies for cognitive symptoms of the disease. 

“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,” says Nandakumar Narayanan, MD, PhD, associate professor of neurology at the UI Carver College of Medicine and senior author of the new study, which is published in the Journal of Neurology, Neurosurgery & Psychiatry.

“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.” 

EEG: a potential tool for predicting cognitive function in Parkinson’s 

The brain recordings were made using a very old, widely available technology called electroencephalography (EEG), which measured low-frequency brain waves, known as delta and theta waves, in the frontal region of study participants’ brains.

The UI team found that reduced strength of these specific brain waves when a patient is required to engage in thinking is strongly linked to cognitive dysfunction in PD. The findings suggest that EEG, which is also inexpensive and non-invasive, might be useful for diagnosing cognitive impairment in PD patients. 

“Traditional methods for diagnosing cognitive problems often involve time-consuming pen and paper tests and require a neurologist to administer and interpret the tests. In addition, because these traditional tests can be ‘learned,’ they cannot be used repeatedly over time for the same patient,” says Narayanan, who also is a neurologist with UI Health Care and a member of the Iowa Neuroscience Institute.

“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 EEG measurements might also be useful for monitoring and fine tuning the cognitive side effects of medications and brain simulation used to treat for Parkinson’s disease. Eventually, EEG could even provide a basic assay to determine whether new treatments for PD are effective at improving cognitive function. 

Diminished brain signal linked to cognitive problems in Parkinson’s 

Lastly, the study, which is one of the largest to date, involving 100 PD patients across the full spectrum of cognitive function from healthy to dementia, and 49 demographically similar control participants, reveals a fundamental insight into the role of the brain signal being measured by the EEG electrode.  

All the participants completed three different tasks that are commonly used to assess cognitive control, and while they were doing the task, a single EEG electrode measured the strength of the low frequency delta and theta brain waves from their frontal cortex. 

Narayanan’s team found that diminished cognitive function was correlated with diminished strength of low frequency brain waves while the patient was doing a task. Importantly, it did not matter which cognitive task the patient was doing during the measurement.  

“Surprisingly, 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 explains.  

“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.

“That process— cue, engage, respond—might be enough to determine where patients are on the cognitive status scale and whether they have the potential to improve.” 

Narayanan says this insight might also be an opportunity to help patients. Potentially “cueing” Parkinson’s patients to engage in a task— whether it’s walking, talking or thinking, might improve how well they perform the task. If this is true, it would have important implications for the way rehabilitation, occupational, and speech therapists help patients with PD. 

The next steps for Narayanan’s team are to investigate the mechanisms that link diminished delta and theta brain waves to worse cognition in PD, and to better understand how EEG technology might be used to improve diagnosis or even treatment of cognitive dysfunction in patients with PD. 

In addition to Narayanan, the research team included Arun Singh, PhD, at University of South Dakota; Rachel Cole, Arturo Espinoza, and Jan Wessel at the UI; and James Cavanagh at the University of New Mexico.

Funding: The research was funded in part by grants from the National Institute of Neurological Disorders and Stroke. 

About this Parkinson’s disease research news

Author: Jennifer Brown
Source: University of Iowa
Contact: Jennifer Brown – University of Iowa
Image: The image is credited to Neuroscience News

Original Research: Open access.
“Evoked mid-frontal activity predicts cognitive dysfunction in Parkinson’s disease” by Nandakumar Narayanan et al. Journal of Neurology Neurosurgery & Psychiatry

Abstract

Evoked mid-frontal activity predicts cognitive dysfunction in Parkinson’s disease

Background

Cognitive dysfunction is a major feature of Parkinson’s disease (PD), but the pathophysiology remains unknown. One potential mechanism is abnormal low-frequency cortical rhythms which engage cognitive functions and are deficient in PD. We tested the hypothesis that mid-frontal delta/theta rhythms predict cognitive dysfunction in PD.

Method

We recruited 100 patients with PD and 49 demographically similar control participants who completed a series of cognitive control tasks, including the Simon, oddball and interval-timing tasks. We focused on cue-evoked delta (1–4 Hz) and theta (4–7 Hz) rhythms from a single mid-frontal EEG electrode (cranial vertex (Cz)) in patients with PD who were either cognitively normal, with mild-cognitive impairments (Parkinson’s disease with mild-cognitive impairment) or had dementia (Parkinson’s disease dementia).

Results

We found that PD-related cognitive dysfunction was associated with increased response latencies and decreased mid-frontal delta power across all tasks. Within patients with PD, the first principal component of evoked electroencephalography features from a single electrode (Cz) strongly correlated with clinical metrics such as the Montreal Cognitive Assessment score (r=0.34) and with National Institutes of Health Toolbox Executive Function score (r=0.46).

Conclusions

These data demonstrate that cue-evoked mid-frontal delta/theta rhythms directly relate to cognition in PD. Our results provide insight into the nature of low-frequency frontal rhythms and suggest that PD-related cognitive dysfunction results from decreased delta/theta activity. These findings could facilitate the development of new biomarkers and targeted therapies for cognitive symptoms of PD.