Cortical Representation Of Sweet And Salty Taste In Human Brain Studied With FMRI

Taste is a special and basic function of oral. The flow of taste information from taste receptors in the oral is not only to modulate food intakes through projection on subcortical area, but also conduct conscious sensation and discrimination of taste on cerebral cortex area, so as to influence emotional and mental activation of human, Taste function and brain function are closely related.Although tradition neurophysiology and neuroanatomy have accumulated a lot of knowledge and theory about the formation of taste organ, anatomic constitution of taste pathways, transduction of taste signal and classification of tastants through electrophysiological, clinical and anatomical research, but most of the fundamental questions about the central organization of taste are still unanswered, for most of the traditional technique are harmful and cannot be applied to human. With the rapid development of functional imaging techniques, basic change took place in the field of brain research in the last 10 years, and many insights have been gained about the sensory function of brain. But compared with some other sensory such as olfaction, vision and audition, taste attracted much less attention. And research work in this area has just set out in our country.fMRI-BOLD is one of the functional imaging techniques now in widespread use for its better spatial resolution, temporal resolution and completely noninvasivc. Some research work has already been done about gustatory, but the results were not identical. The most great progress in fMRI method recently is the development of event related design, which can avoid many factors interfering with block design, and the latter has been adopted by most of the taste experiment performed so far.In order to find the localization of basic taste cortical area in human brain and make further understanding about the relationship between taste function and brain function, the representation of sweet and salty taste in human brain cortical was investigated with specially designed event- related fMRI in this study. The research can be divided into three parts:Part 1. Cortical representation of sweet taste studied with fMRIObjective: Our purpose was to use fMRI-BOLD to measure brain activation in response to sweet taste stimulus, to find the localization of sweet taste cortical areas in human brain.Materials and methods: fMRI-BOLD scan covering the whole brain was performed on 11 healthy human subjects during event- relate designed stimulation with sweet taste and tasteless control .The fMRI data was analyzed by SPM99(Statistical Parametric Mapping) software with statistic t-test to generate the activation map.Result: Activations were found in bilateral insula and operculum , right prefrontal cortex , bilateral cingulate gyrus, bilateral superior parietal lobule , Wernicke's areas of bilateral parietal lobule ,left superior temporal lobule and premoter cortex of left middle frontal gyrus. Strongest signal was found in right insula and operculum, but the biggest area activatied was in cingulate gyrus. Conclusion: 1. Activations were found not only in insula and operculum and prefrontal cortex described as primary ami secondary gustatory areas by previous anatomical and electrophysiological studies, but also in some other parts besides, indicating the complexity of human gustatory pathways. 2. Activations in insula and operculum and prefrontal cortex were more right cerebral lateralized.Part2. Cortical representation of salty taste studied with fMRIObjective: Our purpose was to use fMRI-BOLD to measure brain activation in response to salty taste stimulus, to find the localization of salty taste cortical areas in human brain.Materials and methods: fMRI-BOLD scan covering the whole brain was performed on 11 healthy human subjects during event- relate designed stimulation with salty taste and tasteless control .The fMRI data was analyzed by SPM99 software with statistic t-test to generate the activation map. Result: activations were found in bilateral insula and operculum , bilateral cingulate gyrus ,claustrum and premoter cortex of left middle frontal gyrus. Strongest signal was found in right insula and operculum, and the biggest area activatied was in cingulate gyrus. Conclusion: 1 Activations were found in primary gustatory areas insula and operculum but not in secondary gustatory areas prefrontal cortex. 2. Activations were also found in some other parts beside traditional gustatory areas, indicating the complexity of human gustatory pathways. 3. Activations in insula and operculum and prefrontal cortex were right cerebral lateralized to some extend.Part3. Comparative study between Cortical representation of sweet and salty taste with fMRIObjective: Our purpose was to use fMRI-BOLD to measure brain activation in response to sweet taste and salty taste stimulus, to find the similarity and difference between localizations of sweet and salty taste cortical areas in human brain and make further understanding about the central organization of taste. Materials and methods: fMRI-BOLD scan covering the whole brain was performed on 11 healthy human subjects during event- relate designed stimulation with sweet taste, salty taste and tasteless control .The fMRI data was analyzed by SPM99 software with statistic t-test to generate the activation map. Result: Activations induced by both sweet and salty stimuli were found in bilateral insula and operculum, bilateral cingulate gyrus and premoter cortex of left middle frontal gyrus. Right prefrontal cortex, bilateral superior parietal lobule , Wernicke's areas of bilateral parietal lobule ,left superior temporal lobule was found only activated by sweet stimulus,whereas claustrum was found only activated by salty stimulus .Strongest signal was found in right insula and operculum,but the biggest area activatied was in cingulate gyrus by both stimuli.