This study explores the use of multifunctional, non-invasive spinal cord transcutaneous stimulation (scTS) to address axial motor symptoms, particularly gait dysfunction, in Parkinson's disease (PD). These symptoms, resistant to levodopa and inadequately managed by deep brain stimulation (DBS), arise from maladaptive spinal network changes. A non-invasive approach like scTS could overcome limitations associated with invasive spinal cord stimulation (SCS), which requires surgical implantation and lacks adaptability in stimulation site adjustments. Gait dysfunction in PD stems from disrupted interactions between spinal and supraspinal networks. scTS provides a non-invasive alternative, shown to enhance locomotor functions in conditions such as spinal cord injury, stroke, and cerebral palsy. This study hypothesizes that scTS applied at multiple spinal levels-cervical (C3-C4), thoracic (T11-T12), and lumbar (L1, L2-L3)-can synergistically activate locomotor central pattern generators (CPGs) and improve gait and postural control in PD. Additionally, it is hypothesized that proprioceptive input, combined with scTS, can counteract disruptions in spinal networks and restore voluntary movement. The primary goal is to evaluate the effects of scTS on stepping performance, postural control, and locomotor recovery in PD. Specific objectives include: 1. Enhancing Locomotor Networks * Determine optimal scTS parameters for inducing rhythmic stepping in PD patients. * Assess interactions between spinal and supraspinal networks during imagined stepping under scTS in a gravity-neutral setting. 2. Improving Postural Networks o Evaluate the effectiveness of scTS in restoring postural control and integrating postural-locomotor functions. 3. Facilitating Neuroplasticity for Movement Recovery o Combine scTS with activity-based recovery training to promote adaptive plasticity in spinal and cortical networks, reducing freezing of gait (FOG). The research will measure scTS's capacity to generate coordinated stepping and postural movements, integrate proprioceptive feedback, and induce long-term improvements in gait parameters. By targeting spinal locomotor and postural systems, scTS offers a novel, non-invasive approach to addressing gaps in the management of PD gait dysfunction. This work has the potential to significantly enhance the quality of life for individuals with PD, providing a safe, adaptable, and patient-centered therapeutic solution.