Evoked Potentials Analysis Of Magnetic Stimulation On Acupoint Of Shenmen (HT7)

Magnetic stimulation is a kind of stimulating therapy, it stimulates neural organization by injecting time-variant current and induces time-variant pulsed magnetic field to induces current in biological tissues. Because of advantages of painless, non-invasive and operating simply, it is widely used in the study of activity and cognitive function and related clinical treatment.Modern medicine has proved that acupoint has the physics and chemical relative specificity of acoustics, optics, electricity, magnetic, temperature, ion concentration etc. Acupoint can be seen as an actor which can not only accept information from out of body but also transfer information from body to outside. The acupuncture is familiar to us as a method of stimulation. Magnetic stimulation to acupoint also can be a new stimulation method, it can induce current in tissue to affect and control the information of body.Acupuncture imaging is a new subject which is popular in recent years. The feature of EEG in scalp or inside of brain are imaged in time or space domain by analyzing evoked EEG under stimulation on acupoints. It is a new way to evaluate traditional acupuncture effects by magnetic stimulation on acupoints.This thesis combined EEG analysis with magnetic stimulation on acupoints, compared EEG signals of different frequencies and different stimulation states using nonlinear analysis and brain source localization techniques, and analyzed and evaluated the effect of magnetic stimulation on Shenmen acupoint. Main tasks as follows:1. EEG induced by the magnetic stimulation of different frequencies was collected and analyzed by magnetic stimulation on Shenmen point. Experiments used three frequencies of 0.5Hz, 1Hz and 3Hz. In each frequency, four states of quiet, magnetic stimulation, mock stimulation and mock point are studied in order to compare the differences between them. The results show that magnetic stimulation as well as the other three states has a certain degree of specificity. It shows that magnetic stimulation on Shenmen has a certain impact on brain function obviously.2. Signals were processed in off-line after the experiment. Sample Entropy (SampEn) was calculated. The results showed that the SampEn of the 3Hz magnetic stimulation is significantly lower than that of the mock point stimulation, 1Hz and 0.5Hz samples have no statistical significance. Reduction of SampEn indicates that the complexity of the brain lower and the brain become more stable and orderly. Therefore, the results in the complexity point of view prove that 3Hz frequency magnetic stimulation on Shenmen can strongly inhibite the neural excitability.3. Evoked potentials of EEG in the experiment were extracted. EEG evoked potential amplitudes in three frequencies and four states were observed and compared. The results showed that all of four states in 3Hz magnetic stimulation have not evoked potentials, but 1Hz and 0.5Hz magnetic stimulation groups and mock point groups evoked P150 component on behalf of the major thinking process. P150 amplitudes of the stimulation group and the mock point group were analyzed. 1Hz magnetic stimulation amplitude was significantly higher than that of mock acupoint group, which indicated that 1Hz magnetic stimulation on Shenmen can induce more cognitive activities than mock point stimulation. 0.5Hz magnetic stimulation and mock point stimulation have no significant difference. Evoked potentials produced by 3Hz magnetic stimulation is too weak to reflect the effect of magnetic stimulation.4. Dipole tracing analysis was made with EEG evoked potentials at P150 component of 1Hz and 0.5Hz of the magnetic stimulation groups and the mock point groups. The results showed that 1Hz and 0.5Hz magnetic stimulation induced several dipoles in P150 component on cingulate gyrus on behalf of cognitive and emotional controlling, while the mock point stimulation induced P150 localized in the cingulate gyrus, left middle frontal gyrus and the central back. It shows that the brain function area focus on thinking, information processing area by magnetic stimulation on Shenmen for 1Hz and 0.5Hz. The 1Hz and 0.5Hz stimulation on mock point localized the brain source more diffused, positioning in the thinking process area, language area and sports areas. It implies that magnetic stimulation on Shenmen point may control the function target on thinking.