BOLD fMRI assessment of the functional response to taste stimulation in rat brain

Introduction In mammals, the process of encoding taste information into taste perception extends from the receptor level to the primary gustatory cortex. The neurons in the gustatory cortex are multimodal; they respond not only to the 5 basic tastes—salty, sour, bitter, sweet, and umami—but also to the textures, temperature, and viscosity of foods. Thus, the neurons in the gustatory cortex are involved in the complex processing of a tastant. Electrophysiological examination has long been used to investigate the gustatory system [1], and recently, optical imaging using intrinsic signals has been used to identify the in vivo encoding process for basal tastants in rat and pig gustatory cortex [2, 3]. However, because of the spatial limitations of these techniques, some aspects of taste information processing have not been conclusively clarified, such as the process by which the gustatory cortex uses spatial codes in the cortical taste area to characterize taste information. In this study, we performed BOLD fMRI measurements at 7 T in an animal system to investigate the process by which taste information is encoded in this system.