Mass General - Division of Clinical Research

Age 18-65 years old (inclusive) - Ability to give written consent and participate in behavioral intervention in English - Willingness to attend weekly treatment sessions over live video, daily self-administered transcutaneous auricular vagus nerve stimulation (taVNS) sessions, and engage in homework during treatment - Avoidance of alcohol, nicotine, and caffeine for 24 hours prior to study session - Diagnosis according to the Rome IV criteria for both epigastric pain syndrome and postprandial distress syndrome subtypes - Stable medical treatment for functional dyspepsia (FD) during 1 month before the study and during the study period

• Previous receipt of cognitive behavioral therapy (CBT) for gastrointestinal symptoms - Enteral or parenteral feeding - Previous gastrointestinal surgery, electrolyte disturbances, kidney dysfunction, renal insufficiency, or iron overload disorders - Estimated Glomerular Filtration Rate (eGFR) < 60 - Medications that affect gastrointestinal motility in addition to medications or products containing tetrahydrocannabinol (THC) will be stopped at least 7 days prior to the start of the study and for the duration of the study. However, anti-depressants (SSRI's, TCA's) may be allowed in order to reduce the risk of worsening neuropsychiatric disease, though it will be up to the study team and the Principal Investigator whether subjects on anti-depressants will be able to participate in the study - Intellectual disability by history - Diabetes, mitochondrial disease, severe autonomic dysfunction, and small fiber polyneuropathy - No active clinical acupuncture therapy - Illicit drugs or opioid usage - History of arrhythmias - Current pregnancy/breastfeeding - Contraindications for magnetic resonance imaging (MRI) (implanted ferromagnetic objects, claustrophobia) - Weight > 450 lbs. (limit of the MRI table) - Allergy to pineapple (used in the test meal during MRI) - Any other condition interfering with study requirements, according to the Investigator