Cortical Activation Induced By Intra-oral Stimuli With Cold & Heat Water In Humans: Evidence From FMRI

The perception of intra-oral foodstuffs involves a complex interaction of gustatory, olfactory, tactile and thermal information. A full understanding of the cerebral processing of intra-oral perception requires a determination of how each of these perceptual characteristics is represented within the human brain. Thermal sensory is one of the most important oral sensory. The temperature of food in the mouth is important to their palatability. All of unique features of intra-oral thermo-sensory make it significant for the insight of its central processing. Recently, studies of intra-oral thermo-sensory transmission pathway were paid close attention to.2005 year, foreign scholars first report the representation in any primate cortical area of oral temperature. This representation of temperature is likely to be involved in the regulation of food and fluid intake. Moreover, dysfunction of this system in cortical area of oral temperature is likely to lead to abnormal sensations produced by oral stimuli. This will provided new thinking for etiology studying of oral sensation system illness and provided therapy strategy for abnormal oral sensations. However there is no reports that reflected the intra-oral thermo-sensory pathway in the level of cerebral cortex in humans.Functional magnetic resonance imaging (fMRI) is an advanced non invasive neuroimaging technique which has high spatial and temporal resolutions, and has been rapidly developed these years. The emerging of fMRI allows investigators to assess functional -anatomical concordances bilaterally and three-dimensionally and it provided advanced techniques for insight into intra-oral thermo-sensory cortical representation in humans. However, cortical areas of the human brain activated bycold and hot water stimuli with fMRI technique is remain unknown.Data demonstrate the ability of fMRI technique to study gustation in humans. However, the neural representations of intra-oral stimulation with water have received little attention. Cortical area of the human brain activated by the delivery of small quantities of water to the mouth with fMRI is remained unknown.In this study, we first employed advanced high spatial resolution neuroimaging method fMRI techniques to explore cerebral activation in intra-oral thermal stimulation with cold, warm and hot water through self-made water delivery device. This may provide bases for clinical study. Intra-oral thermo-sensory perception is an complex process involving reward behavioral factors. So in this study, we will study this respect involving in intra-oral water temperature .This study consists of the following three parts: 1. Cortical responses of intra-oral water stimulation measured with fMRIObjective: To discuss the neural representations of in normal humans intra-oral stimulation with 23°C water with non-invasive fMRI measurements, provide a contrast for intra-oral cold and hot water sensory study. Methods: Six healthy right-handed subjects (of which 3 were males) participated in the study to receive 23°C deionized distilled water stimuli in mouth (group W-g-L). The experimental protocol consisted of a block-design using 5 stimulus. Water stimuli were delivered to the subject's mouth through self-made polythene tubes that were held between the left of lips. BOLD functional MRI scan covering the whole brain was carried out. The fMRI data were analyzed by SPM99 software with statistic t-test to generate the activation map. Results: Increased BOLD signals during intra-oral 23°C water stimulation were found bilateral significantly activations within the peri-sylvian including pre/post-central gyrus (BA3/1/2/43/4 ),and Rolandic cortices, the largest magnitude of activation was found in left insular/ operculum BA44, also in the right OFC(BAll) as well as middle frontal gyrus. BOLD signals were also increased unilaterally in right ACC (BA24) ,parietal lobule (BA7)and midbrain red nucleus, in left insular(BA13) and parietal lobule (BA40).Conclusions: much of the activityinduced by water reflects intra-oral somatosensory or motor processing. Water's ability to activate nonspecific somatosensory, thermal or taste processing in the insular/operculum region and OFC involved in pleasantness of water. These findings highlight the complex and distributed processing of different aspects of intra-oral perception, and emphasize the importance of controlling for the effects of water and other non-gustatory factors when investigating the functional neuroanatomy of taste or temperature.2. Functional activity mapping during intraoral stimuli with cold water: evidence from fMRIObjective: To evaluate the feasibility of fMRI on the location of brain regions related to cold stimulated with water. Distinguish the different brain regions between intra-oral 4°C cold and 23°C water sensation. Methods: 6 healthy volunteers selected to perform the fMRI study, all of which are right handed.4°C (group C-g-L) deionized water Stimuli were delivered to the subject's mouth through polythene tubes that were held between the left of lips. Group W-g-L is as a control. Block designed fMRI scan covering the whole brain was carried out. Comparison of the fused cross-sectional map of the two groups C-g-L /W-g-L. Results: The group C-g-L showed significant bilateral activations OFC(BAll)and BA44,pre/post-central gyrus oral sensory/motor (BA3/1/2/43/4) and parietal lobule (BA7,40) ,PMC(BA6) especially in insula/SII;BOLD signals were also found unilaterally in right ACC (BA24),lingual gyrus and temporal lobe, midbrain red nucleus and occipital lobe. Compared groups C-g-L/W-g-L, overlapping brain areas included pre/post-central gyrus oral sensory/motor, ACC, insula/operculum. Conclusions: l.The volume of activation was remained significantly when cold water was contrasted with warm water. This indicates that specific functional regions of the human brain cortex can be activated in fMRI study when the cold water stimulated;2.Cold water's ability to activate OFC involved in hedonic or reward value of water. 3 Cerebral activation during intra-oral stimuli with heat water: fMRIObjective: To evaluate the feasibility of fMRI on the location of brain regionsrelated to hot stimulated with water. Distinguish the different brain regions between intra-oral 56°C and 23°C water sensation. Methods: 6 healthy volunteers selected to perform the fMRI study, all of which are right handed. 56°C (group H-g-L) deionized water Stimuli were delivered to the subject's mouth through polythene tubes that were held between the left of lips. Group W-g-L is as a control. Block- designed fMRI scan covering the whole brain was carried out. Comparison of the fused cross-sectional map of the two groups H-g-L/W-g-L. Results: The group H-g-L showed robust activations in left thalamus and bilateral activations insular/operculum, pre/post-central gyrus oral sensory/motor, Signals in motor language area(BA44) ,PMC(BA6) ,parietal lobule(BA40,7) were strong, BOLD signals were also found unilaterally right frontal Lobe, striatum and precuneus. Compared groups H-g-L/W-g-L, brain areas including pre/post-central gyrus (oral sensory/motor), ACC, insular/operculum are overlapping. Conclusions: The magnitude and volume of activation was remained significantly when hot water was contrasted with warm water. This indicates that specific functional regions of the human brain cortex can be activated by intra-oral hot water stimuli in fMRI study.4 Comparison of human cerebral activation patterns during intra-oral warmth, cold and heat.Objective: This study aimed to investigate the comparative cerebral activation to non-painful warm and cold stimuli, to determine whether there are differences in the spatial pattern and intensity of activity within human brain when different forms and intensities of innocuous thermal stimuli are experienced.Methods: 12 healthy volunteers were selected to receive 4°C, 23°C and 56°C deionized water stimuli the subject's mouth through polythene tubes that were held between the lips. Block design were adopted, fMRI scan covering the whole brain was carried out. Scanning and analysis procedure were same as experiment one and two. In addition, volumes of interest (VOI) were chosen on the basis of the results of previously somatotopic thermal perception fMRI studies.. Comparison of the fused cross-sectional map of the two group W-g-L/C-g-L, W-g-L/H-g-L and C-g-L/H-g-L. Results: Comparedgroup C-g-L/W-g-L and H-g-L/W-g-L, overlapping brain area were included pre/post-central gyrus oral sensory/motor, ACC, insular/operculum is overlapping. Comparisons of rCBF response magnitude were made among stereotactically concordant brain regions that showed significant responses in three group of this study. Six regions were responsive in both the heat and cold conditions: the insula, bilateral pre/post-central gyrus oral sensory/motor, parietal lobule (BA7, 40) , premotor cortex PMC(BA6), Motor language area(BA44) ,anterior cingulate cortex, except in right lingual gyrus, midbrain red nucleus in cold conditions, in the left ventral posterior thalamus and bilateral activations parietal lobule in hot conditions. These regions showed a higher increase in rCBF response magnitude in the heat group than in the cold group. Highly significant increases in rCBF were found in the left thalamus in hot, OFC in cold. Conclusions: 1 These results agree with previous neuroimaging findings in somatotopic thermal perception, except for that motor cortex including OFC and BA44 have strong signals during cold or heat water stimuli;Intra-oral stimuli with hot water can activate especially thalamus and cold water can activate especially OFC.2 This suggests that similar neural networks may process warm and cold sensory inputs and the differential patterns may be activated by the qualities of thermal stimuli.3 This activity appears to represent a specific neural correlate of thermal stimulation, and may reflect gustatory.