Diagnostic and Interventional Neuroradiology, University Hospital, RWTH Aachen University, Pauwelsstraße 30, 52074, Aachen, Germany.
Scent and Care, Symrise AG, Holzminden, Germany.
Brain Struct Funct. 2021 Jan;226(1):247-261. doi: 10.1007/s00429-020-02178-4. Epub 2020 Dec 23.
Exploring the potential of eucalyptol as a masking agent for aversive odors, we found that eucalyptol masks the olfactory but not the trigeminal sensation of ammonia in a previous study. Here, we further investigate the processing of a mixture consisting of eucalyptol and ammonia, two olfactory-trigeminal stimuli. We presented the two pure odors and a mixture thereof to 33 healthy participants. The nostrils were stimulated alternately (monorhinal application). We analyzed the behavioral ratings (intensity and pleasantness) and functional brain images. First, we replicated our previous finding that, within the mixture, the eucalyptol component suppressed the olfactory intensity of the ammonia component. Second, mixture pleasantness was rated differently by participants depending on which component dominated their mixture perception. Approximately half of the volunteers rated the eucalyptol component as more intense and evaluated the mixture as pleasant (pleasant group). The other half rated the ammonia component as more intense and evaluated the mixture as unpleasant (unpleasant group). Third, these individual differences were also found in functional imaging data. Contrasting the mixture either to eucalyptol or to both single odors, neural activation was found in the unpleasant group only. Activation in the anterior insula and SII was interpreted as evidence for an attentional shift towards the potentially threatening mixture component ammonia and for trigeminal enhancement. In addition to insula and SII, further regions of the pain matrix were involved when assessing all participant responses to the mixture. Both a painful sensation and an attentional shift towards the unpleasant mixture component complicates the development of an efficient mask because a pleasant perception is an important requirement for malodor coverage.
我们研究了桉叶油醇作为厌恶气味掩蔽剂的潜力，发现桉叶油醇在前一项研究中掩蔽了氨的嗅觉但没有掩蔽三叉神经感觉。在这里，我们进一步研究了由桉叶油醇和氨两种嗅觉-三叉神经刺激物组成的混合物的处理。我们向 33 名健康参与者呈现了两种纯气味和混合物。鼻孔被交替刺激（单鼻孔应用）。我们分析了行为评分（强度和愉悦度）和功能脑图像。首先，我们复制了之前的发现，即在混合物中，桉叶油醇成分抑制了氨成分的嗅觉强度。其次，混合物的愉悦度因参与者而异，具体取决于哪种成分主导他们对混合物的感知。大约一半的志愿者认为桉叶油醇成分更强烈，并评估混合物更愉悦（愉悦组）。另一半则认为氨成分更强烈，并评估混合物不愉快（不愉快组）。第三，这些个体差异也在功能成像数据中发现。与桉叶油醇或两种单一气味相比，只有在不愉快组中发现混合物的神经激活。在前脑岛和 SII 中的激活被解释为对潜在威胁的混合物成分氨的注意力转移和三叉神经增强的证据。除了脑岛和 SII，在评估所有参与者对混合物的反应时，还涉及疼痛矩阵的其他区域。当评估所有参与者对混合物的反应时，不仅有疼痛感，而且对不愉快混合物成分的注意力转移也使高效掩蔽变得复杂，因为愉悦的感觉是掩盖恶臭的一个重要要求。
