The artificial sweeteners are added in much food and drink as a low-calorie sweetener. These sweeteners were originally developed for the purpose of treatment for adiposity, diabetes and the metabolic syndrome. These sweeteners include saccharin, sucralose, aspartame and acesulfame K. However, it was reported recently that the excessive intake of the artificial sweetener causes an onset risk of diabetes by the enterobacterial flora change and excessive eating. By the rat experiment, the rat got to eat lots of the sweet diet and gained weight by intake of the artificial sweetener. But at all events I have not yet understood the detailed mechanism well. The functional MRI (fMRI) is laboratory procedure using the blood oxygenation-level dependent (BOLD) signal by MRI as change of the brain activity by noninvasive procedure. Therefore, fMRI might be useful tool for the examination of the brain function including brain activity of a taste stimulation. In this study, we compared the rats brain activity by the taste stimulation of acesulfame K against sucrose using fMRI. And then, the rat brain activity by acesulfame K stimulation was different from by sucrose.　In addition, the brain activity of the rats given sweeteners before for two weeks was different from the rats not given sweeteners.