- Sixty normal subjects, males and females within the ages of 18 to 65 years, will be studied. Normal control subjects will be recruited for voluntary participation through poster advertisements. A normal subject is defined as a person with no gastrointestinal (GI) symptoms; no prior history of peptic ulcer disease or irritable bowel disease; no previous history of a GI motility disorder (including, but not limited to, achalasia, gastroparesis); on no medications for GI disorders; no history of prior surgery on the GI tract (esophagus, stomach, large or small intestine); and a normal physical examination.