This observational study's main goal is to learn more about the neural mechanisms during movement in Parkinson's disease. Furthermore, it aims to inspire personalised treatment options.

Participants will undergo a protocol that involves walking and gait-related motor tasks, such as seated stepping. During the protocol, brain activity will be recorded.

Parkinson's Disease (PD) is the second most common neurodegenerative disease accompanied by motor impairment [1]. Although symptomatic treatments like medication with Dopamine equivalents and deep brain stimulation (DBS) are available, the effects are very heterogeneous among patients and often cease over time.

This study aims to generate insights into the neural mechanisms of PD by determining neural biomarkers for gait. The insights of this study may further inspire personalised treatment approaches.

The primary objective is to identify neural biomarkers for gait. It is hypothesised that characteristic neural oscillations are underlying kinematic patterns in healthy participants and PD patients.

The secondary objective is to compare the neural activity during gait and a seated lower limb motor task between healthy participants and PD patients. To this end, the investigators hypothesise that neural correlates of gait and of a seated lower limb motor task differ between healthy participants and PD patients.

60 participants will be included, 30 healthy participants and 30 PD patients. All participants must be older than 18 years and give informed consent. Potential participants will be pre-screened and will be informed about the study via phone call/email. Before any study procedure, participants will give informed consent as documented by signature. Afterwards, inclusion/exclusion criteria, medical history and participant characteristics will be assessed. PD patients must be of postural instability and gait difficulty sub-type.

The study consists of one session of approximately 2.5 hours. During this session, electroencephalography (EEG) in healthy participants and EEG + local field potentials of the subthalamic nucleus from implanted DBS-electrodes in PD patients will be recorded during standardised gait sequences and a seated lower limb motor task. Furthermore, a short-term neuromodulation task will be investigated.

Gait-related parameters will be recorded using motion capture, surface electromyography (EMG) and accelerometers. Gait characteristics, including symmetry, coordination, variability, and resilience will be assessed. All recording devices are approved on the market. The protocol of the session slightly differs between healthy participants and PD patients since no DBS electrodes are implanted in healthy participants, but still allows for comparison between the groups.

Inclusion Criteria:

All participants

• must have given informed consent as documented by signature
• agree to comply with the study procedures

Healthy control group

• no neurological, orthopedic, or rheumatologic disease history
• no identified sensory impairment.
• no epilepsy and self-diagnosed acute or chronic psychiatric disorders

Parkinson's Patients

• non-tremor dominant idiopathic PD patients
• presence of postural instability (UPDRS >1 for postural instability [17]), gait disturbance, and absence of other causes of reduced balance
• Implanted with Percept™ PC neurostimulator
• Able to be in the stimulation OFF

Exclusion Criteria:

• Relevant cognitive impairment, with a score on Montréal Cognitive Assessment (MoCA) < 20
• History of physical or neurological condition that interferes with study procedures
• Social and/or personal circumstances interfering with the ability to come to the session

Participants will be recruited among students, employees and associated persons of ETH Zürich, the University of Zürich, the University Hospital of Zürich, and Balgrist University Hospital and other centers.