Objective We used functional magnetic resonance imaging (fMRI) to explore the effects of noxious coldness and non-noxious warmth on the magnitude of cerebral cortex activation during intraoral stimulation with water.Methods Six male and female subjects were subjected to whole-brain fMRI during the phasic delivery of non-noxious hot (23 ℃) and noxious cold (4 ℃) water intraoral stimulation. A block-design blood oxygenation level-dependent fMRI scan covering the entire brain was also carried out.Results The activated cortical areas were as follows: left pre-/post-central gyrus, insula/operculum, anterior cingulate cortex (ACC), orbital frontal cortex (OFC), midbrain red nucleus, and thalamus. The activated cortical areas under cold condition were as follows: left occipital lobe, premotor cortex/Brodmann area (BA) 6, right motor language area BA44, lingual gyrus, parietal lobule (BA7, 40), and primary somatosensory cortex SⅠ. Comparisons of the regional cerebral blood flow response magnitude were made among stereotactically concordant brain regions that showed significant responses under the two conditions of this study. Compared with non-noxious warmth, more regions were activated in noxious coldness, and the magnitude of activation in areas produced after non-noxious warm stimulation significantly increased. However, ACC only significantly increased the magnitude of activation under noxious coldness stimulation.Conclusion Results suggested that a similar network of regions was activated common to the perception of pain and nopain produced by either non-noxious warmth or noxious coldness stimulation. Non-noxious warmth also activated more brain regions and significantly increased the response magnitude of cerebral-cortex activation compared with noxious coldness. Noxious coldness stimulation further significantly increased the magnitude of activation in ACC areas compared with noxious warmth.
