Zang Yunpeng, Chen Ben, Hummel Thomas
Smell and Taste Clinic, Department of Otorhinolaryngology, TU, Dresden, Germany; Department of Otorhinolaryngology, The Affiliated Hospital Xuzhou Medical University, Xuzhou, China.
Smell and Taste Clinic, Department of Otorhinolaryngology, TU, Dresden, Germany; Department of Psychiatry, The Affiliated Brain Hospital of Guangzhou Medical University (Guangzhou Huiai Hospital), Guangzhou, China.
J Neurosci Methods. 2020 Jul 15;341:108754. doi: 10.1016/j.jneumeth.2020.108754. Epub 2020 May 4.
Numerous studies investigated the central-nervous processing of olfactory information in humans, often based on functional MRI studies. However, when describing the olfactory perception, the course of olfactory sensations over time has received little attention although this constitutes a fundamental portion of the experimental paradigm. Hence, the aim of this study was to evaluate overall perception and the perception of odors over the time course of repeated odorous stimulation under different conditions of stimulus presentation.
Twenty-eight subjects with a normal sense of smell were asked to lie in a mock MRI scanner during the experiment. Three conditions of odor presentations were Tubing, (odors presented intranasally with separate tubing for each nostril), mask (odors presented to a mask covering the subject's nose) and vacuum (odors presented into the bore of the sham scanner). A pleasant odor (peach) and an unpleasant (fish) odor were presented using a computer-controlled olfactometer. Participants were asked to evaluate intensity and pleasantness of the odors. They also rated the comfortability of each presentation mode. For the vacuum and mask conditions, subjects were tracked with the time course of the odor intensity.
For all sessions, intensity was influenced by conditions (F = 29.6, p < 0.001, ηp² = 0.8, mask > tube > vacuum) and odors (F = 11.8, p = 0.003, ηp² = 0.4, fish > peach). Pleasantness was influenced by odors (F = 26.2, p = 0.001, ηp² = 0.593, peach > fish), comfortability was significantly influenced by conditions (F = 9.3, p = 0.002, ηp² = 0.5, vacuum > mask > tube). For peach odor, pleasantness was positively correlated with intensity (r = 0.3, p = 0.03) and negatively with fish odor intensity (r = -0.4, p < 0.001). Overall, the onset latency of intensity ratings (mean = 3.5 s, SD = 2.6) was significantly longer than the offset latency (mean = 1.6 s, SD = 0.8) (t = 3.5, p = 0.001). For the amplitude, conditions had a significant effect (F = 4.5, p = 0.04, ηp² = 0.2, mask > vacuum).
Perceived odor intensity was affected by the odor presentation being strongest in the mask condition, whereas this was not different for odor pleasantness. The vacuum condition was rated as most comfortable. Within the present design, the latency of onset and offset does not seem to be influenced by conditions, odors and blocks. Models of fMRI analyses should be adjusted to account for this shift in odor intensity perception.
众多研究探讨了人类嗅觉信息的中枢神经处理过程，这些研究通常基于功能磁共振成像（fMRI）研究。然而，在描述嗅觉感知时，嗅觉感受随时间的变化过程却很少受到关注，尽管这是实验范式的一个基本部分。因此，本研究的目的是评估在不同刺激呈现条件下，重复进行气味刺激过程中气味的整体感知以及随时间变化的感知情况。
28名嗅觉正常的受试者在实验过程中躺在模拟磁共振成像扫描仪中。气味呈现的三种条件分别是：管道法（通过单独的管道将气味经鼻内分别输送到每个鼻孔）、面罩法（将气味施加到覆盖受试者鼻子的面罩上）和真空法（将气味输送到假扫描仪的孔腔内）。使用计算机控制的嗅觉计呈现一种愉悦气味（桃子味）和一种不愉快气味（鱼腥味）。要求参与者评估气味的强度和愉悦度。他们还对每种呈现方式的舒适度进行评分。对于真空法和面罩法条件，记录受试者对气味强度随时间的变化情况。
在所有实验环节中，强度受条件影响（F = 29.6，p < 0.001，ηp² = 0.8，面罩法 > 管道法 > 真空法）以及气味影响（F = 11.8，p = 0.003，ηp² = 0.4，鱼腥味 > 桃子味）。愉悦度受气味影响（F = 26.2，p = 0.001，ηp² = 0.593，桃子味 > 鱼腥味），舒适度受条件显著影响（F = 9.3，p = 0.002，ηp² = 0.5，真空法 > 面罩法 > 管道法）。对于桃子味气味，愉悦度与强度呈正相关（r = 0.3，p = 0.03），与鱼腥味强度呈负相关（r = -0.4，p < 0.001）。总体而言，强度评分的起始潜伏期（平均值 = 3.5秒，标准差 = 2.6）显著长于终止潜伏期（平均值 = 1.6秒，标准差 = 0.8）（t = 3.5，p = 0.001）。对于振幅，条件有显著影响（F = 4.5，p = 第0.04，ηp² =第0.2，面罩法 > 真空法）。
气味呈现方式会影响所感知的气味强度，面罩条件下最强，而气味愉悦度不受此影响。真空条件被评为最舒适。在当前设计中，起始和终止潜伏期似乎不受条件、气味和实验分组的影响。功能磁共振成像分析模型应进行调整，以考虑气味强度感知的这种变化。
