Objective: Dynamics in EEG activity such as slowing in low-frequency bands has been reported in Parkinson’s disease (PD). The objective of the present study was to find out the activity pattern (power and cortical sources)  in lower  bands of EEG in PD with or without dementia.

Background: In Parkinson’s disease, dysfunction in various cortical and subcortical pathways lead to the alteration in activity of brain depicted by EEG waves. Alteration in the EEG activity pattern and the sources of delta and theta bands may cause deficits in information processing in PD. Pathologically altered activity of these bands may predict the severity and stage of the disease and could serve as a noninvasive biomarker for early and accurate diagnosis of cognitive impairment as well as of dementia.

Methods: Parkinson’s Patients with MMSE scores ≤ 24 PD demented (PDD, n=28); MMSE score >24 as PD non-demented (PDND, n = 30) and Controls with MMSE score > 26 as Controls (Con, n=28) were taken for the study. EEG was recorded for 5 min each during Eyes closed and Eyes open conditions by using 128 channel EEG net . Absolute mean power was calculated using FFT algorithm in MATLAB. Source localization analysis was done using sLORETA software. Kruskal test followed by rank sum test in MATLAB was used. EEG sources compared by  t-tests. Significance was determined with a p-value of <0.05.

Results: At rest, EEG power in delta and theta bands was significantly higher  in PDD compared to Control as well as PDND. In PDND compared to Control, power was present in theta band only. In PDND compared to Controls, EEG sources in delta band showed higher activation in frontal, limbic, occipital, temporal and sub lobar lobes, except in parietal lobe (Precuneus gyri BA, 7) where predominantly lower activation was seen. In theta band higher activation was observed in Inferior Frontal Gyrus (BA 47), anterior cingulate gyrus (BA 24, 32), and lower activation in medial frontal gyrus (BA 6), middle frontal gyrus (BA 10). PDD compared to Control as well as PDND primarily had higher activation in medial frontal gyrus (BA 10) and middle temporal lobe (BA 21) in both delta and theta bands.

Conclusions: Higher power and differential pattern of cortical source activation in slow bands (delta and theta) is an indicator of altered brain activity in PDD patients. algorithms used for the present study could be used to differentiate the onset and progression of dementia from PDND to PDD.

References: W. Klimesch. EEG alpha and theta oscillations reflect cognitive and memory performance: a review and analysis. Brain Research Reviews, 1999; (29): 169–195

Bonanni L et al., EEG comparisons in early Alzheimer’s disease, dementia with Lewy bodies and Parkinson’s disease with dementia patients with a 2-year follow-up. Brain. 2008; 131(3):690-705

Caviness JN, Hentz JG, Belden CM, Shill HA, Driver-Dunckley ED, Sabbagh MN, et al. Longitudinal EEG changes correlate with cognitive measure deterioration in Parkinson’s disease. J Park Dis. 2015; 5(1):117–24

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MDS Abstracts - https://www.mdsabstracts.org/abstract/resting-state-modulations-of-eeg-low-frequency-bands-in-parkinsons-disease/