| 【Background and objective】In the human sensory system, researchs of visual andauditory are common. But the olfactory system, which is the most directly and closelycontact with the brain, because of its complexity, there has not been able to find aappropriate methods to explore its pathway and mechanism. The animal experimentproved that eugenol and rosewood can improve the learning and memory function ofmice and relieves their depression-like behaviors. This function is achieved by olfactorypathways such as hippocampus, amygdala, hypothalamus and some other brain areas.The change of human brain function activated by olfactory can be evaluated byfunctional imaging and nerve electrophysiology. Among this, PET-CT combined thePositron Emission Tomography (PET) and computer tomography(CT).This technologycan directly reflected the activation of brain cells through the use of physiological tracerin brain imaging, so it has a unique advantage on olfactory research compared withother technologies.This experiment use eugenol and citral as the smell stimulation. compare the brainactivation level under the influence through the PET-CT technology, and apply theStatistical patametric mapping(SPM) for data processing. We aimed to build a model ofthe correlation between the sense of smell and brain function and discusses the brainfunction inhalated by aromatic substances. At the same time,we use SPM to analyze thebrain glucose metabolism changes of Alzheimer’ s disease(AD),and discussed therelationship between olfactory pathway and AD.【Methods】（1）Six healthy volunteers participated in the test. First time all subjests were scanned without inhalation. The results were recorded as a blank control. Thengive volunteers eugenol and citral as the stimulation. All subjects were scanned twice.The data were processed with Matlab6.5, SPM2, MRIcro. The group of eugenol andcitral were compared with the blank group,and summarized their imagingcharacteristics.（2）Ten AD patients were compared with ten healthy volunteers,who matched inage,sex and education years by SPM. We aimed to analysis the changes in cerebralglucose metabolism in patients with AD.【Results】（1）After smell eugenol,activation were presented in the frontal lobe(BA10), orbitofrontal gyrus (BA11), the medial temporal lobe (BA37,38), cingulatedgyrus (BA25,32).In the frontal lobe,the activation in the right hemisphere were largerthan in the left.After smell citral,activation were presented in the frontal lobe (BA9,10),orbital frontal cortex (BA11,46,47), superior temporal gyrus (BA22), cingulate gyrus(BA23,31). There were no significant dominant hemisphere founded.（2） In the AD patients,there were decreasing cerebral glucose metabolism in Frontallobe(BA5,9), parietal lobe(BA13,20), temporal lobe (BA7,40), cingulate gyrus (BA23)and occipital area.And the decreasing in the left hemisphere were larger than in theright.【Conclusions】The imaging technology are important methods to analysis therelationship between olfactory and human brain function, According to the results ofthis research, after smell fragrant, activation were presented in the front lobe,orbitofrontal cortex, the medical temporal lobe and cingulated gyrus. It showed that theodor awaked the emotional brain regions, and this effect is achieved by olfactorypathway. Combined with the previous animal studies, it confirms that the odor activesthe mood, learning and memory related brain regions through the olfactory pathway. AD is closely associated with olfactory system. According to the results of thisresearch, the reduced brain regions in AD patients are associated with the activationpresented by inhalation. It showed the possibility of the prevention and treatmentthrough the olfactory pathway. |
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