Department of Food Science and Technology, The Ohio State University, Columbus, OH, USA.
Chem Senses. 2018 Feb 26;43(3):197-203. doi: 10.1093/chemse/bjy007.
Odorants are perceived orthonasally (nostrils) or retronasally (oral cavity). Prior research indicates route of delivery impacts odorant perception, pleasantness, and directed behaviors thus suggesting differential processing of olfactory information. Adaptation is a form of neural processing resulting in decreased perceived intensity of a stimulus following prolonged and continuous exposure. The present study objective was to determine whether route of delivery differentially impacts olfactory adaptation and whether cross-adaptation occurs between orthonasal and retronasal pathways. Linalool (12%) or vanillin (25%) were delivered orthonasally [6 L/min (LPM)] and retronasally (8 LPM) in air phase through a custom-built olfactometer. Perceived odorant intensity was collected every 5 min over 10-min exposure. Immediately following the exposure period, cross-adaptation was assessed by shunting the delivery of the odorant from the nostrils to the oral cavity, or vice versa. A control study was also completed in which subjects underwent the orthonasal adaptation protocol using stimulus concentrations matched to the intensity of restronasal stimuli (e.g., 1.5% linalool and 6.25% vanillin). Following orthonasal delivery of both high and low vanillin concentrations, results showed perceived intensity decreased significantly at 5 and 10 min. High concentrations of orthonasal linalool similarly decreased significantly whereas lower concentrations decreased but did not reach statistical significance. Linalool and vanillin delivered retronasally did not adapt as perceived intensity actually increased significantly following a 10-min exposure. In addition, evidence of cross-adaptation was not obvious following extended odorant exposure from either delivery pathway. This study suggests that olfactory processing may be affected by the route of odorant delivery.
气味通过鼻前（鼻腔）或鼻后（口腔）途径被感知。先前的研究表明，传递途径会影响气味的感知、愉悦度和引导行为，这表明嗅觉信息的处理方式存在差异。适应是一种神经处理形式，表现为在长时间连续暴露于刺激物后，感知到的刺激强度降低。本研究的目的是确定传递途径是否会对嗅觉适应产生差异影响，以及鼻前和鼻后途径之间是否会发生交叉适应。芳樟醇（12%）或香草醛（25%）以空气相通过定制的嗅觉仪以 6 LPM（升/分钟）的流速鼻前（鼻腔）和鼻后（口腔）传递。在 10 分钟的暴露过程中，每 5 分钟收集一次感知到的气味强度。在暴露期结束后，通过将气味从鼻腔转移到口腔，或反之，来评估交叉适应。还完成了一项对照研究，其中受试者使用与鼻后刺激强度匹配的刺激浓度（例如，1.5%芳樟醇和 6.25%香草醛）进行鼻前适应方案。在鼻前输送高和低浓度的香草醛后，结果表明，在 5 分钟和 10 分钟时，感知到的强度明显降低。高浓度的鼻前芳樟醇也明显降低，而较低浓度的则降低，但未达到统计学意义。鼻后输送的芳樟醇和香草醛没有适应，因为在 10 分钟暴露后，感知到的强度实际上显著增加。此外，在从任一传递途径延长暴露于气味后，并没有明显的交叉适应证据。本研究表明，嗅觉处理可能受到气味传递途径的影响。
