Studying the pathophysiology of late stage Parkinson’s disease (PD) – after the patients have experienced severe neuronal loss – has helped develop various symptomatic treatments for PD (e.g., deep brain stimulation). However, it has been of limited use in developing neuroprotective disease-modifying therapies (DMTs), because DMTs require interventions at much earlier stages of PD when vulnerable neurons are still intact. Because PD patients exhibit various non-motor prodromal symptoms (ie, symptoms that predate diagnosis), understanding the pathophysiology underlying these symptom could lead to earlier diagnosis and intervention. In my talk, I will present a recently elucidated example of how PD pathologies alter the channel biophysics of intact vagal motoneurons (known to be selectively vulnerable in PD) to drive dysautonomia that is reminiscent of prodromal PD. I will discuss how elucidating the pathophysiology of prodromal symptoms can lead to earlier diagnosis through the development of physiological biomarkers for PD.