Resting-state alpha reactivity is reduced in Parkinson disease and associated with gait variability

BackgroundThe extent to which the cholinergic system contributes to gait impairments in Parkinsons 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. MethodsEyes-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. ResultsAlpha reactivity was reduced in people with PD compared to healthy individuals (U = 105, p = 0.017); the rank-biserial correlation of 0.447 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 (rho = -0.437 to -0.532). ConclusionsReduced alpha reactivity in PD is driven by levels of global cognition and suggests impaired cholinergic function in PD. 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.