RecruitingDevice studyEffect of Vagal Nerve Stimulation on Gastric Motor FunctionsThe specific aim of this study is to compare simultaneous assessment of gastric emptying and gastric accommodation in response to a caloric meal In patients who have previously undergone activation of left cervical VNS for the treatment of medication-resistant depression. Our hypothesis is that cervical VNS increases gastric accommodation and accelerates gastric emptying compared to a bank of healthy control data.