Resting-state Alpha Reactivity Is Reduced in Parkinson's Disease and Associated With Gait Variability

Background
The extent to which the cholinergic system contributes to gait impairments in Parkinson’s disease (PD) remains unclear. Electroencephalography (EEG) alpha reactivity, which refers to change in alpha power over occipital electrodes upon opening the eyes, has been suggested as a marker of cholinergic function. We compared alpha reactivity between people with PD and healthy individuals and explored its potential association with gait measures.
Methods
Eyes-closed and eyes-open resting-state EEG data were recorded from 20 people with idiopathic PD and 19 healthy individuals with a 64-channel EEG system. Alpha reactivity was calculated as the relative change in alpha power (8-13 Hz) over occipital electrodes from eyes-closed to eyes-open. Gait spatiotemporal measures were obtained with an electronic walkway.
Results
Alpha reactivity was reduced in people with PD compared to healthy individuals (U = 105, P = .017); the rank-biserial correlation of .447 indicated a moderate effect size. When controlling for global cognition (Mini Mental State Examination), the group difference in alpha reactivity was no longer significant. Alpha reactivity associated with measures of gait variability only (ρ = −.437 to −.532).
Conclusions
Resting-state alpha reactivity is reduced in PD, suggesting impaired cholinergic function. Reduced alpha reactivity was associated with greater gait variability, indicating a role of the cholinergic system in the mechanisms underlying gait variability. Therefore, the cholinergic system may represent a target for treatments aiming to reduce gait variability and alpha reactivity should be further explored as an endpoint for clinical trials.