Older adults, and particularly those with Parkinson disease (PD), may experience walking difficulties that negatively impact their daily function and quality of life. People that have PD plus dementia are also likely to experience walking difficulties. This project will examine the impact of music and mentally singing on walking performance, with a goal of understanding what types of rhythmic cues are most helpful. Pilot work from the investigators suggests that imagined, mental singing (i.e., singing in head) while while walking helps people walk faster with greater stability, whereas walking to music also helps people walk faster but with reduced stability.

In this study, the investigators will recruit people who have PD plus dementia. The investigators will compare walking while mentally singing and walking while listening to music, using personalized cues tailored to each person's walking performance. The investigators hypothesize temporal variability of gait will be lower in the mental singing and singing conditions compared to listening to music; and that mental singing, singing, and listening to music will elicit similar improvements in stride length.

During this observational study, participants will attend one visit in the laboratory. The visit will include participants wearing wearable sensors during the following tasks: walking with no cues (UNCUED), walking while listening to music (MUSIC), and walking while mentally singing (MENTAL SINGING). The wearable sensors will measure gait parameters including gait speed, stride length, and stride time variability.

Inclusion Criteria:

• at least 30 years of age
• diagnosis of idiopathic, typical Parkinson disease according to the UK Brain Bank Criteria
• Hoehn & Yahr stages 2-3 (mild to moderate disease severity)
• normal or corrected hearing
• stable on all PD medications for at least 2 months prior to study entry
• dementia as defined by a Clinical Dementia Rating (CDR) score of 0.5-1.0 (very mild to mild dementia)
• score of ≥ 1 on the MDS-UPDRS-III Item #10 indicating observable gait impairment
• a score of 1 or less on item #7 on the freezing of gait questionnaire
• able to walk for 10 continuous minutes independently

Exclusion Criteria:

• diagnosis of any other neurological condition
• unstable medical or concomitant illnesses or psychiatric conditions which, in the opinion of the investigators, would preclude successful participation
• cardiac problems that interfere with ability to safely participate (i.e., uncontrolled congestive heart failure, myocardial infarction in past 6 months, complex cardiac arrhythmias, significant left ventricular dysfunction, dyspnea on exertion, chest pain or pressure, resting tachycardia (>100 beats/min); uncontrolled BP (resting systolic BP >160 mmHg or diastolic BP >100 mmHg))
• orthopedic problems in the lower extremities or spine that may limit walking (i.e., severe arthritis, spinal stenosis)
• uncontrolled tremor or dyskinesia while on PD medications

During single lab visit that took a few hours

Monitoring in real time during single session during which participants were continually supervised