Department of Psychotherapy and Psychosomatic Medicine, TU Dresden Faculty of Medicine Carl Gustav Carus, Dresden, Germany.
Clinic for Diagnostic and Interventional Neuroradiology, TU Dresden Faculty of Medicine Carl Gustav Carus, Dresden, Germany.
Neuroimage. 2021 Apr 1;229:117782. doi: 10.1016/j.neuroimage.2021.117782. Epub 2021 Jan 23.
The human sense of smell is highly individual and characterized by a strong variability in the perception and evaluation of olfactory stimuli, depending on cultural imprint and current physiological conditions. Since this individual perspective has often been neglected in fMRI studies on olfactory hedonic coding, this study focuses on the neuronal activity and connectivity patterns resulting from subject-specific olfactory stimulation.
Thirty-one normosmic participants took part in a fMRI block designed paradigm consisting of three olfactory stimulation sessions. The most pleasant and unpleasant odors were individually specified during a pre-test for each participant and validated in the main experiment. Mean activation and functional connectivity analysis focusing on the right and left piriform cortex were performed for the predefined olfactory regions-of-interest (ROIs) and compared between the three olfactory conditions.
Individual unpleasant olfactory stimulation as compared to pleasant or neutral did not alter mean BOLD activation in the predefined olfactory ROIs but led to a change in connectivity pattern in the right piriform cortex.
Our data suggests that the individual pleasantness of odors is not detectable by average BOLD magnitude changes in primary or secondary olfactory brain areas, but reflected in temporal patterns of joint activation that create a network between the right piriform cortex, the left insular cortex, the orbitofrontal cortex, and the precentral gyrus. This network may serve the evolutionary defense mechanism of olfaction by preparing goal-directed action.
人类的嗅觉具有很强的个体差异，其对嗅觉刺激的感知和评估存在很大的可变性，这取决于文化印记和当前的生理状况。由于在 fMRI 嗅觉愉悦编码研究中经常忽略这种个体差异，因此本研究侧重于由特定于个体的嗅觉刺激引起的神经元活动和连接模式。
31 名嗅觉正常的参与者参与了一项 fMRI 块设计范式，该范式由三个嗅觉刺激阶段组成。在每个参与者的预测试中，单独确定了最愉快和最不愉快的气味，并在主要实验中进行了验证。针对预定义的嗅觉感兴趣区域（ROI）进行了平均激活和功能连接分析，并比较了三种嗅觉条件之间的差异。
与愉快或中性相比，个体不愉快的嗅觉刺激并未改变预定义嗅觉 ROI 中的平均 BOLD 激活，但导致右侧梨状皮层的连接模式发生变化。
我们的数据表明，气味的个体愉悦感不能通过初级或次级嗅觉脑区的平均 BOLD 幅度变化来检测，而是反映在共同激活的时间模式中，这些模式在右侧梨状皮层、左侧岛叶皮层、眶额皮层和中央前回之间形成了一个网络。该网络可能通过准备目标导向的行动来为嗅觉的进化防御机制提供服务。
