Effects of anti-parkinsonian medication on gait during internal and external rhythmic auditory cueing in PD

Introduction: External and internal auditory cueing strategies improve gait function, including velocity and stride length, in people with Parkinson disease (PD). Further, internal cueing can reduce gait variability, a measure associated with falls. In the present study, we asked whether the efficacy of external and internal rhythmic cues depends on dopaminergic status, i.e., OFF vs. ON medication. This question is relevant to the real-world use of cueing, as dopaminergic medication responsiveness fluctuates for individuals. We measured gait while participants with PD walked with an external cue (music playing aloud) and with an internal cue (mentally singing) in both OFF and ON medication states. We hypothesized both cues would improve gait regardless of medication status. Methods: = 36) walked at a preferred pace without cues (Uncued), while a song played aloud at 120% of each participant's uncued cadence (Music), and while singing the same song in their head (Mental) in the OFF state and again after taking their normal dose of anti-PD medication. Variables were collected using Opal Sensors. Two, 2 (ON, OFF) × 3 (Uncued, Music, Mental) repeated-measures multivariate ANOVAs were conducted: one for mean gait outcomes (cadence, velocity, stride length, double limb support) and one for their linear variability. Results: Medication improved spatial measures of gait but did not change cadence. Both Music and Mental singing increased velocity, stride length, and cadence. For measures of linear variability, Music trials had statistically higher variability than Mental trials. There was an interaction effect between medication and cueing condition for double limb support; in the OFF-medication state, Music had longer double support times than Uncued and Mental singing. Conclusion: Cueing strategies improved gait regardless of medication status, suggesting they may be useful throughout the day despite medication fluctuations. However, internally-based mental singing cues produced greater benefits than external music cues, in both the ON and OFF state, for measures of gait variability. Further investigation of the efficacy of cues within and across anti-PD medication cycles would be helpful to understand their utility in the real world.