| Summary: | 碩士 === 逢甲大學 === 自動控制工程所 === 96 === The cerebrum is one of important organs for human. Recently there are many studies to discover brain function by traditional EEG and novel functional MRI (fMRI). The electrical signal of neural activity can directly recorded by EEG, but fMRI only measure the local blood oxygen level that effect by neural activity. A lot of researches point out the activated signal could be influenced by hypercapnia in fMRI study, due to the change of local blood flow during hypercapina. According our best knowledge, the relationship between hypercapnia and neural activity has not been fully investigated in human. In this study, we estimate the relationship by the change of visual evoked potential (VEP) under multi-level carbon dioxide concentration. Six healthy volunteers were recruited, each undergoing 4 separate experiments by inhaling gas mixtures with different fractions of CO2 (room air, 3%,5%, and 7%). Visual stimulation was given in each experiment contained 3 phases, prehypercapnic, hypercapnic, and posthypercapnic via a LED flashing. After comparing the results in different phases, we found the decreased amplitude of VEP with increase of inhaled CO2 fractions. It is not significantly different when inhaling 3% CO2 gas (Wilcoxon, P>0.05) but in 5% and 7% (Wilcoxon, P<0.01). However, the latency of VEP is not affected by hypercapnia in the experiment of transient visual evoked potential （Friedman, P>0.05）. Because the amplitude and latency reflect the neural activity, we suggest the effect of hypercapnia is necessary to be sufficient consideration in clinical cerebral functional research.
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