Effects of Vagal Dysfunction on Gastrointestinal and Inflammatory Pathways in HIV

Inclusion Criteria : * Greater than or equal to18 years old (18 to 64 Years, 65 Years and Over) * Documentation of HIV-1 infection * Stable CART for greater or equal to 3 months * HIV-1 viral load \<100 copies/ml (within 3m) * No diagnosis known to cause autonomic or GI dysfunction other than HIV (e.g. Parkinson's disease, diabetes, peptic ulcer disease, infectious diarrhea) * Willing to refrain from nicotine use for 24h prior to all testing * No contraindication to autonomic testing (e.g. uncontrolled glaucoma, heart rate not under sinus control) * No medications with significant autonomic or GI effects (e.g. sympathomimetics, prokinetics, anti-diarrheals, antibiotics) * Urine test negative for stimulants and opiates/opioids and pregnancy test (if applicable) Exclusion Criteria: * Dysphagia to food or pills * Known or suspected obstructive disease of the GI tract (e.g. bezoar, strictures, fistulae, physiologic GI obstruction) * GI surgery within 3m, Crohn's disease, diverticulitis, any electromechanical medical device (e.g. pacemaker, infusion pump). * Contraindication to pyridostigmine (e.g. mechanical intestinal or urinary obstruction, hypersensitivity to pyridostigmine, cardiac arrhythmias, asthma, chronic obstructive pulmonary disease); use of pyridostigmine within the past 6m. * History of intracranial aneurysm/hemorrhage, brain tumor, abnormal neck anatomy, or implants or metal hardware near site of stimulation; exposure to VNS within the past 6m.