Vagal Nerve Stimulation for Interoception Modulation

Explore the effects of variable ingested volumes and auricular transcutaneous vagal nerve stimulation (taVNS) on brain and stomach outcomes in healthy adults.

Inclusion Criteria: * Male and female patients aged 18 and 65 years old (inclusive) * Comprehension of instructions * Avoidance of alcohol, nicotine, and caffeine for 25 hours prior to study session Exclusion Criteria: * BMI (Body Mass Index) more than 32 and/or weight \> 235 lbs. (limits of the MRI table) * Any other significant medical disease (systemic or CNS), psychiatric disorder, or chronic pain condition/s * Epilepsy or a prior history of seizures * Psychotropic medications or other medications that effect neurovascular coupling (i.e. fMRI) * Subjects taking illicit drugs or opioids * Allergy to pineapple (used in the test meal during MRI) * Contraindications for MRI: High magnetic fields may pose a serious health hazard to subjects with implanted ferromagnetic objects. Every subject in this study will be carefully screened before entering the high magnetic field shielded room to collect a precise outline of the subject's medical history. Subjects with the following characteristics/disease will not be eligible to participate in the study: -History of Head Trauma -Any metallic implants (e.g. braces or permanent retainers) -Tattoos with metallic ink above the nipple line -Surgical Aneurysm Clips -Cardiac Pacemaker -Prosthetic Heart Valve -Neurostimulator -Implanted pumps -Cochlear Implants -Metal rods, Plates -Screws -Recent Previous Surgery -IUD -Hearing Aid -Dentures (which might create NMR artifacts) -Metal Injury to eyes -Pregnancy or plans to become pregnant -Breast Feeding -Meniere's Disease -Transdermal (skin) patches such as NicoDerm (nicotine for tobacco dependence), Transderm Scop, or Ortho Evra (birth control) -Non-normally cycling females -Claustrophobia