Effects of Internal and External Cues on Brain Activity and Gait in Parkinson's Disease: Findings From BARC-PD.

BackgroundInternal and external cueing strategies are often applied to alleviate gait deficits in Parkinson's disease (PD). However, it remains unclear which type of cueing strategy is most effective at different disease stages. The underlying neural mechanisms of response to cueing are also unknown.ObjectiveTo investigate the immediate response of multiple brain cortical regions and gait to internal and external cueing in people at different stages of PD.MethodsPeople with PD (n = 80) were split into groups dependent on their disease stage (Hoehn and Yahr [H&Y] stage I to III). Participants performed a baseline walk without cues followed by randomized cued walking conditions (internal and external [visual, auditory and tactile] cues). A combined functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) system assessed cortical brain activity while walking. Wearable inertial sensors assessed gait.ResultsCue-related gait improvements were not influenced by H&Y stage; moderate or large effect sizes were only observed for internal cueing and external visual cueing. fNIRS findings suggested cortical response was similar across H&Y stages, with increased activity in the prefrontal cortex with internal cues; and increased activity in the primary motor and visual cortices with external cues. However, EEG showed that people with PD in H&YIII had higher parietal alpha power than those in H&YI in the auditory, tactile, and visual cueing conditions.ConclusionGait improvement with cueing was similar across PD stages and underpinned by cognitive, motor, and/or sensory neural processing within selective brain regions that may be influenced by PD stage (i.e., parietal cortex).