Frasnelli Johannes, Schuster Benno, Hummel Thomas
Cognitive Neuroscience Unit, Montreal Neurological Institute, Montreal, Quebec, Canada.
Cereb Cortex. 2007 Oct;17(10):2268-75. doi: 10.1093/cercor/bhl135. Epub 2006 Dec 5.
The olfactory and the trigeminal systems have a close relationship. Most odorants also stimulate the trigeminal nerve. Further, subjects with no sense of smell exhibit a decreased trigeminal sensitivity with unclear underlying mechanisms. Previous studies indicated that single stages of trigeminal processing may differently be affected by olfactory loss. A better knowledge of adaptive and compensatory changes in the trigeminal system of subjects with acquired anosmia (AA) will improve the understanding of interactive processes between the 2 sensory systems. Thus, we aimed to assess trigeminal function on different levels of processing in subjects with AA. Subjects with AA showed larger electrophysiological responses to irritants obtained from the mucosa than healthy controls. On central levels, however, they exhibited smaller event-related potentials and psychophysical measures to irritants. Over 9 months, they exhibited an increase in trigeminal sensitivity. Subjects with recovering olfactory function showed an even more increased peripheral responsiveness to irritants. These data suggest dynamic mechanisms of mixed sensory adaptation/compensation in the interaction between the olfactory and trigeminal systems, where trigeminal activation is increased on mucosal levels in subjects with AA and amplified on central levels in subjects with a functioning olfactory system.
嗅觉系统和三叉神经系统关系密切。大多数气味分子也会刺激三叉神经。此外，嗅觉丧失的受试者三叉神经敏感性降低，但其潜在机制尚不清楚。先前的研究表明，三叉神经处理的单一阶段可能会因嗅觉丧失而受到不同影响。更好地了解获得性嗅觉丧失（AA）受试者三叉神经系统的适应性和代偿性变化，将有助于增进对这两个感觉系统之间交互过程的理解。因此，我们旨在评估AA受试者在不同处理水平上的三叉神经功能。与健康对照组相比，AA受试者对从黏膜获取的刺激物表现出更大的电生理反应。然而，在中枢水平上，他们对刺激物的事件相关电位和心理物理学测量结果较小。在9个月的时间里，他们的三叉神经敏感性有所增加。嗅觉功能正在恢复的受试者对刺激物的外周反应性增加得更多。这些数据表明，在嗅觉系统和三叉神经系统的相互作用中，存在混合感觉适应/代偿的动态机制，其中AA受试者的黏膜水平上三叉神经激活增加，而嗅觉系统功能正常的受试者在中枢水平上三叉神经激活增强。
