 20-70 year-old volunteers who hold legitimate licenses were recruited to have gastroscopy or colonoscopy under intravenous anesthesia with propofol, and before endoscopy using driving simulator and NCT to measure patients driving ability and cognitive function as a baseline, in the same way, assessing patients driving ability and cognitive function after 2h, 4h of the endoscopy , meantime collecting blood samples and separating blood plasma, using HPLC High Performance Liquid Chromatography to measure blood concentration of propofol. 