Objective: To examine the relationship between spectral power of resting state EEG (rsEEG) and cognition in Parkinson’s disease (PD).

Background: Alzheimer patients have reduced rsEEG power in the alpha band but increased theta power. Similar effects have been reported for PD patients with mild cognitive impairment (PD-MCI). The current study compared rsEEG in PD patients, classified as meeting or not meeting criteria for mild cognitive impairment (PD-MCI; PD-N).

Method: Fifty-five PD patients were recruited from a Movement Clinic and diagnosed as showing PD-MCI (N=25; MDS Level II criteria) or as PD-N (N=30). A group of age-matched healthy controls (N=27) was also recruited. Participants undertook a 10-min resting state EEG session (wakeful eyes-closed session; 64 electrodes). Visual inspection and automated algorithms were used to identify and reject artefacts. EEG was re-referenced to common average of all electrodes and spectral power was calculated using FFT with a Hanning window from 2-s EEG segments. Hierarchical Bayesian regressions, accounting for age, sex, and education, were used to examine EEG (1) across groups and (2) a global cognition score derived from comprehensive testing across 5 cognitive domains.

Results: For alpha, we found lower spectral power for the PD-MCI group compared to HC (-0.4; 95% credible intervals (CI): -0.2, -0.6), accounting for total power, but no difference in the PD-N group. Only the PD-MCI group also had lower individual alpha frequency (IAF; peak frequency). IAF was positively associated with the global z-score across all PD patients (β=0.30, CI: 0.1–0.59); this was prominent in both anterior and posterior regions. By contrast, global power for theta was higher (0.67, 95% CI: 0.07–1.77) in the PD-MCI group than the HC group; The PD-N group had intermediate values. Increased theta power in PD-MCI was most evident in the left anterior region and bilateral posterior regions. The transition frequency from theta to alpha band had a non-significant association with global cognition (β=0.18, 95% CI: -0.02­­–0.37).

Conclusion: By adding a group of PD-N patients, and using detailed neuropsychological assessments, we confirm prior work that decline in cognitive function is associated with a reduction in peak frequency and power in the alpha frequency band. Further evidence on the slowing of synchronized activity in PD as cognition declines, particularly longitudinal studies, may enhance the value of rsEEG as a biomarker in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/resting-state-eeg-spectral-power-in-parkinsons-disease/