Hummel T, Iannilli E, Frasnelli J, Boyle J, Gerber J
Department of Otorhinolaryngology, University of Dresden Medical School, Smell & Taste Clinic, Dresden, Germany.
Ann N Y Acad Sci. 2009 Jul;1170:190-5. doi: 10.1111/j.1749-6632.2009.03910.x.
Although numerous fMRI studies have been performed on the processing of olfactory information, the intranasal trigeminal system so far has not received much attention. In a pilot study stimulants were presented within a constantly flowing airstream birhinally to activate the olfactory (phenylethyl alcohol, H(2)S) or the trigeminal (CO(2)) nerves. Both olfactory and trigeminal stimulation activated the ventral insular cortex. Intranasal trigeminal stimulation additionally led to an activation of the midbrain, superior temporal gyrus, anterior caudate nucleus, and the dorsolateral orbitofrontal cortex. Cerebellar activation was reduced relative to odorous stimuli. For all stimuli, right-sided activity was more pronounced. These results suggested that processing of intranasal activation follows a pattern which is, at least to some degree, similar for both trigeminal and olfactory stimulation. This and results from several other studies emphasize the fact that there is a high degree of interaction between the different aspects of the chemical senses, also in the sense that chemosensory-induced activation in the nasal cavity is processed in similar cortical networks. Interactions between the olfactory and trigeminal system can also be seen in patients with acquired olfactory loss, who exhibit reduced trigeminal sensitivity, possibly due to the lack of a central-nervous interaction. Both the orbitofrontal cortex and the rostral insula appear to be of significance in the amplification of trigeminal input, which is missing in patients with olfactory loss.
尽管已经进行了大量关于嗅觉信息处理的功能磁共振成像（fMRI）研究，但鼻内三叉神经系统迄今为止尚未受到太多关注。在一项初步研究中，刺激物在持续流动的气流中双侧鼻腔给予，以激活嗅觉神经（苯乙醇、H₂S）或三叉神经（CO₂）。嗅觉和三叉神经刺激均激活了腹侧岛叶皮质。鼻内三叉神经刺激还额外导致中脑、颞上回、尾状核前部和背外侧眶额皮质的激活。相对于气味刺激，小脑激活有所减少。对于所有刺激，右侧活动更为明显。这些结果表明，鼻内激活的处理遵循一种模式，至少在某种程度上，三叉神经和嗅觉刺激的模式相似。这一结果以及其他几项研究的结果强调了这样一个事实，即化学感觉的不同方面之间存在高度的相互作用，也就是说，鼻腔内化学感觉诱导的激活在相似的皮质网络中进行处理。嗅觉和三叉神经系统之间的相互作用也可见于后天性嗅觉丧失的患者，他们表现出三叉神经敏感性降低，这可能是由于缺乏中枢神经系统的相互作用所致。眶额皮质和嘴侧岛叶在放大三叉神经输入方面似乎都具有重要意义，而这在嗅觉丧失的患者中是缺失的。
