Study was stopped due to technical issues with the ANSAR equipment, lack of research personnel caused by COVID-19 restrictions imposed at our site, and recent departure of the PI and study chair from our research institute.

Gastroparesis Patients and Healthy Controls ages 20-49 will be asked to participate in an observational study measuring vagal activity following food ingestion in order to establish parameters of autonomic nerve/vagal function in healthy human subjects compared to those with gastroparesis. Information generated from this study may be used in the future to establish what is normal and abnormal enteric vagal tone and how much vagal nerve stimulation treatment may be required to help patients with gastroparesis.

Impaired function of the vagus nerve has been documented in many chronic diseases such as diabetes, heart disease, and chronic pain, as well as gastrointestinal diseases such as irritable bowel syndrome, inflammatory bowel disease, and delayed stomach emptying (gastroparesis).

Current technology only allows for measurement of vagal nerve activity that regulates the heart and diagnostic tests focus specifically on cardiac vagal activity. Measuring vagal nerve activity as it pertains to the gastrointestinal system is an unmet medical need. Its importance will continue to grow since vagal nerve stimulation is being used increasingly in a myriad of different diseases, and currently there is no way of knowing if patients are getting too little or too much stimulation.

In this study, the gastrointestinal vagus nerve will be activated using normal stimulants like food ingestion and vagal activity will be measured using current non-invasive technology. Patients with gastroparesis and healthy controls will be asked to come in fasting, fill out surveys, and complete eating challenges while being connected to an autonomic function testing machine. Exploratory outcomes will also be measured - Participants will be connected to a Peripheral Intravenous Line in order to collect four vials of blood throughout the two hour clinic visit so that hormonal changes can be studied. Also, exploratory non-invasive electrogastrograms will be recorded remotely both during the autonomic function test and for three consecutive days as participants go about their daily lives.

The investigators' goal is to establish a protocol for measuring gastrointestinal evoked vagal activity and correlating activity with digestive function in both healthy people and gastroparesis patients.

Inclusion Criteria

1. Male or female.
2. Age 20-49 years old.
3. Healthy volunteer or established diagnosis of idiopathic gastroparesis as per AGA (American Gastroenterology Association) guidelines.
4. Participant is capable of giving informed consent.
5. Gastroparesis patients must be on stable doses of medications for gastroparesis for preceding 4 weeks prior to enrollment (including cholinergics, anti-cholinergics, dopamine and serotonin receptor agonists/antagonists, motility agents, neuromodulators, herbals).

Exclusion criteria.

1. Diagnosis of systemic autonomic nerve dysfunction (i.e. POTS, CAN).
2. Surgical-related gastroparesis
3. Extrinsic myopathy or neuropathy causing gastroparesis.
4. Use of narcotic pain medications in the preceding 2 weeks of study enrollment.
5. Patients with enteric feeding tubes or requiring parenteral nutrition.
6. Patients with severe disease flare requiring hospitalization or frequent emergency room visits (last within 3 months or less of enrollment).
7. Untreated significant depression or suicidal thoughts.
8. Pregnant or breast-feeding women.
9. History of gastric pacemaker implantation.
10. Patients with prior gastric surgery, including fundoplication, partial/total gastrectomy, pyloroplasty, or gastric bypass.
11. Patients with implantable electronic devices.
12. Dairy, wheat, or egg allergy/intolerance.
13. Allergy to commercial clinical adhesive for EKG stickers.
14. Non-English speaker and/or hearing impaired (as participants need to follow English verbal commands and cues for the experiment).

60 Patients (20 Gastroparesis and 40 Controls) between the ages of 20-49.