Albrecht Jessica, Kopietz Rainer, Frasnelli Johannes, Wiesmann Martin, Hummel Thomas, Lundström Johan N
Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA 19104, USA.
Brain Res Rev. 2010 Mar;62(2):183-96. doi: 10.1016/j.brainresrev.2009.11.001. Epub 2009 Nov 11.
Almost every odor we encounter in daily life has the capacity to produce a trigeminal sensation. Surprisingly, few functional imaging studies exploring human neuronal correlates of intranasal trigeminal function exist, and results are to some degree inconsistent. We utilized activation likelihood estimation (ALE), a quantitative voxel-based meta-analysis tool, to analyze functional imaging data (fMRI/PET) following intranasal trigeminal stimulation with carbon dioxide (CO(2)), a stimulus known to exclusively activate the trigeminal system. Meta-analysis tools are able to identify activations common across studies, thereby enabling activation mapping with higher certainty. Activation foci of nine studies utilizing trigeminal stimulation were included in the meta-analysis. We found significant ALE scores, thus indicating consistent activation across studies, in the brainstem, ventrolateral posterior thalamic nucleus, anterior cingulate cortex, insula, precentral gyrus, as well as in primary and secondary somatosensory cortices-a network known for the processing of intranasal nociceptive stimuli. Significant ALE values were also observed in the piriform cortex, insula, and the orbitofrontal cortex, areas known to process chemosensory stimuli, and in association cortices. Additionally, the trigeminal ALE statistics were directly compared with ALE statistics originating from olfactory stimulation, demonstrating considerable overlap in activation. In conclusion, the results of this meta-analysis map the human neuronal correlates of intranasal trigeminal stimulation with high statistical certainty and demonstrate that the cortical areas recruited during the processing of intranasal CO(2) stimuli include those outside traditional trigeminal areas. Moreover, through illustrations of the considerable overlap between brain areas that process trigeminal and olfactory information; these results demonstrate the interconnectivity of flavor processing.
我们在日常生活中遇到的几乎每种气味都有产生三叉神经感觉的能力。令人惊讶的是，很少有功能成像研究探索鼻内三叉神经功能的人类神经元相关性，而且结果在某种程度上并不一致。我们利用激活可能性估计（ALE），一种基于体素的定量元分析工具，来分析用二氧化碳（CO₂）进行鼻内三叉神经刺激后的功能成像数据（功能磁共振成像/正电子发射断层扫描），二氧化碳是一种已知专门激活三叉神经系统的刺激物。元分析工具能够识别各研究中共同的激活情况，从而能更确定地进行激活映射。九项利用三叉神经刺激的研究的激活焦点被纳入元分析。我们在脑干、丘脑腹后外侧核、前扣带回皮质、脑岛、中央前回以及初级和次级体感皮层中发现了显著的ALE分数，表明各研究间激活情况一致，这些区域是一个以处理鼻内伤害性刺激而闻名的网络。在梨状皮质、脑岛和眶额皮质（已知处理化学感觉刺激的区域）以及联合皮质中也观察到了显著的ALE值。此外，将三叉神经ALE统计数据与源自嗅觉刺激的ALE统计数据直接进行比较，结果显示激活情况有相当大的重叠。总之，这项元分析的结果以高统计确定性描绘了鼻内三叉神经刺激的人类神经元相关性，并表明在处理鼻内CO₂刺激过程中所募集的皮质区域包括传统三叉神经区域之外的区域。此外，通过说明处理三叉神经和嗅觉信息的脑区之间存在相当大的重叠；这些结果证明了味觉处理的相互关联性。
