愉快及非愉快气体激活相应脑区的功能磁共振成像实验研究

目的 采用功能磁共振成像（fMRI）观察和研究愉快及非愉快气体激活相应脑区的情况并对嗅觉中枢及其通路进行功能定位。方法12名右利手、无嗅觉障碍健康志愿者参加实验。采用乙酸戊酯为愉快刺激气体，吡啶为非愉快气体，组块设计，1．5T MRI行EPI序列扫描，用Matlab5．3及SPM99、Talairach等软件数据后处理。结果愉快及非愉快气体刺激海马回钩，丘脑内侧背核、眶额回皮质均出现明显激活，两种气味均表现为右侧大脑半球优势激活，即右侧额叶上、中、下回、右侧眶额回、右侧海马回钩以及右侧丘脑背内侧核均较左侧半球相应脑区激活明显；与情绪相关脑区亦发现激活，即额内侧回、海马旁回、扣带回、颢上回以及右侧额叶上、中、下回。愉快气体激活大脑前区为主，非愉快气体激活大脑后区明显。结论BOLD-fMRI是研究人类嗅觉功能的有效方法。本研究进一步验证了海马回钩、丘脑内侧背核和眶额回为嗅觉中枢及其重要通路，并且右侧大脑半球为嗅觉“优势半球”；气味嗅觉还引起与情绪相关脑区的激活，并且愉快情绪主要与大脑前部区域有关，不愉快情绪主要与大脑后部区域关系密切。

Functional MRI study on regional brain responses to pleasantand unpleasant odors

Objective To identify regional activation of the human cerebral cortex in response to pleasant and unpleasant odors with functional MRI (fMRI), and to localize the olfactory centers and pathways. Methods Twelve right-handed healthy volunteers were recruited in this study. Two kinds of odors were given to them through the personally developed instrument. One was amyl acetate, which was regarded as pleasant odor, and the unpleasant one was pyridine. Block design was adopted in this experiment, and EPI was performed on 1.5T MRI, the raw fMRI data were processed with Matlab 5.3, SPM 99 and Talairach tool softwares. Results Activation was present in the olfactory centers and important pathways during administration of pleasant and unpleasant odors, such as uncus of hippocampus, lateral medial nucleus of thalamus and orbitofrontal gyru. Both the two odors had more activation in the right hemisphere than the left. For example, the superior, middle, inferior gyrus of right frontal lobe, right orbitofrontal gyrus, right uncus of hippocampus and right lateral medial nucleus of thalamus were activated more prominently than the contralateral corresponding region. The mood related regions were also found to be activated, including medial frontal gyrus, parahippocampal gyrus, cingulate gyrus, superior temporal gyrus and the superior, middle, inferior gyrus of right frontal lobe. Further, it was found that the anterior part of the cerebrum was activated by the pleasant odor and that a more posterior part was activated by the unpleasant odor. Conclusion BOLD-fMRI is an useful method for studying of human olfactory system. The uncus of hippocampus, lateral medial nucleus of thalamus and orbitofrontal gyrus are further proved the olfactory centers and important pathways, and presented dominant in the right hemisphere. In the same time, odors can activate the mood related regions. The pleasant feeling is mainly concerned with the anterior part of the cerebrum, while the unpleasant feeling is involved in the posterior part of the cerebrum.