Older adults, and particularly those with Parkinson disease (PD), may experience walking difficulties that negatively impact their daily function and quality of life. 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. Our pilot work suggests that imagined, mental singing (i.e., singing in your 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 Aim 1, the investigators will compare walking while mentally singing to walking while listening to music, using personalized cues tailored to each person's walking performance. The investigators hypothesize stride time variability will be less in the mental singing condition compared to listening to music; and that mental singing and listening to music will improve gait speed similarly as compared to the uncued condition. The investigators will also test whether finger tapping, a rhythmic task similar to walking in many ways, responds similarly while mentally singing and listening to music.

In Aim 2, the investigator will investigate the brain mechanisms underlying the enhancements in movement performance seen with mental signing or listening to music. The investigators will use magnetic resonance imaging (MRI) to measure brain activity during finger tapping with and without various cues to understand which areas of the brain are more or less responsive to the cues. The investigators hypothesize individuals with PD will exhibit lesser activation of putamen and greater activation of cortical motor areas and cerebellum compared to controls in all tapping conditions; and internal, mental singing during tapping will elicit greater activation of the putamen and lesser activation of cortical motor areas in both groups compared to uncued tapping and tapping while listening to music.

During this observational study, all participants will attend two visits 4-10 days apart. At the first visit, all participants (participants with PD and age-matched controls) will wear wearable sensors during the following tasks: walking with no cues; walking while listening to music; and walking while mentally singing. The wearable sensors will measure gait parameters including gait speed and stride time variability. All participants will also conduct the following tasks while finger tapping on a keyboard: tapping with no cues; tapping while listening to music; and tapping while mentally singing.

At the second visit, all participants (participants with PD and age-matched controls) will perform the following tasks during imaging: uncued tapping; listening to music (no tapping); mentally singing (no tapping); listening to music and tapping; and mentally singing and tapping.

Inclusion Criteria for all participants:

• at least 30 years of age;
• willing and able to provide informed consent;
• right-handed or ambidextrous;
• normal hearing;
• weight less than 250 lbs; and
• able to walk for 10 continuous minutes independently.

Inclusion criteria for participants with PD also include:

• diagnosis of idiopathic, typical Parkinson disease according to the United Kingdom Brain Bank Criteria;
• Hoehn & Yahr stages 2-3 (mild to moderate disease severity);
• stable on all PD medications for at least 2 months prior to study entry;
• a score of 1 or less on item # 7 on the New Freezing of Gait Questionnaire; and
• score of ≥ 1 on the Movement Disorder Society - Unified Parkinson Disease Rating Scale (MDS-UPDRS)-III Item #10 indicating observable gait impairment.

Exclusion Criteria for both groups include:

• diagnosis of any other neurological condition;
• significant cognitive impairment;
• 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);
• contraindications for magnetic resonance imaging (e.g., metallic implants); or
• uncontrolled tremor or dyskinesia (while on PD medications if applicable).

Reporting results separately for group with PD and healthy controls, though both groups were assigned to same walking conditions

Monitoring of participants during two separate visits of a few hours each on 2 different days no more than 2 weeks apart.

Participants were supervised throughout their time in the two sessions so adverse events were monitored continuously