Association of VAgus Nerve Stimulation and Treadmill Training for GAit Rehabilitation in DE Novo Parkinson's Disease

The goal of this clinical trial is to learn if transcutaneous auricular vagus nerve stimulation (taVNS) can improve gait and brain function in people with diagnosis of idiopathic Parkinson's disease (PD) within 6 months. It will also help researchers learn about the safety and biological effects of taVNS when used together with physical therapy. The main questions it aims to answer are: * Does taVNS paired with physical therapy improve walking speed and gait performance in people with PD? * Does taVNS change brain activity or breain perfusion related to movement? * Does taVNS reduce markers of inflammation and neurodegeneration in blood and saliva? Researchers will compare active taVNS to sham (placebo) stimulation to see if active taVNS works better when paired with physical therapy. Participants will: * Attend 12 rehabilitation sessions over 4 weeks (three per week) * Receive either active or sham taVNS during each session while doing treadmill and conventional physical therapy * Undergo gait and cognitive testing, MRI scans, and blood and saliva collection before and after treatment * Return for a follow-up visit four weeks after therapy to check how long the effects last