The development of a novel automated taste stimulus delivery system for fMRI studies on the human cortical segregation of taste

fMRI indicated that the primary taste cortex is activated not only by taste but also by non-taste information from oral stimuli. Head movements caused by swallowing are very critical problem in fMRI and inherent difficulties to modulate taste stimuli in the mouth exist to elucidate functional segregation of human brain. We developed a novel automated taste stimulus delivery system for fMRI studies to segregate the pure taste area in the primary taste cortex in humans. As a novel intra-oral device, an elliptic cylinder was attached to an individual mouthpiece and then subject placed the tongue tip in it. Using a computer-controlled extra-oral device, the solutions ran through the intra-oral device in constant conditions. Three adult volunteers participated in the experimental session, alternately consisting of 30 pairs of taste stimuli (0.5 mol/l sucrose solution) and control (water) blocks. The typical findings of the three subjects revealed activation only in the primary taste cortex (P < 0.001), and none in the secondary taste cortex. This is the first system that delivers the taste stimuli automatically to a standardized area on the subject's tongue under constant conditions, thus allowing us to successfully segregate the pure taste area in the primary taste cortex in humans.