Effects of Transcutaneous Vagus Nerve Stimulation in Parkinson´s Disease

This study aims to determine whether electrical stimulation of the ear, when combined with physical and speech therapy, can improve symptoms in subjects diagnosed with Parkinson´s disease, by comparing two different application sites. Each subject will undergo an initial in-person screening and provide consent before participating in the study. The main questions to answer are: * Does transcutaneous electrical nerve stimulation (tVNS) in the ear paired with physical and speech therapy improve speech and voice-related problems, airway protection, salivation, and swallowing? * Does tVNS paired with physical and speech therapy improve tremor, walking speed, and balance in people with PD? * Does tVNS paired with physical and speech therapy improve heart rate and heart rate variability in people with PD? * Do its effects persist at 8 weeks? Participants will: Attend 12 rehabilitation sessions over 4 weeks (three per week). During each session, participants received either active or sham tVNS, accompanied by speech therapy (once per week), physical therapy (once per week), or conducted alone (once per week). Undergo speech, voice, swallowing, respiratory, gait, balance, tremor, heart rate variability, and cognitive testing, as well as questionnaires regarding the quality of life, before and after treatment. Return for a follow-up visit eight weeks after therapy to check how long the effects last.