模拟脑电节律磁场对记忆的影响(英文)

Effect of magnetic field simulating electroencephalogram rhythm on memory

背景:近年来研究结果表明经颅磁刺激对学习记忆能力产生影响,一些研究也开始探讨在模拟脑电节律条件下的磁场对记忆能力的影响。目的:探讨磁场对记忆再现能力的影响及其作用机制。设计:随机对照实验。单位:天津医科大学医学影像学系和天津大学精密仪器及光电子工程学院。材料:实验于2002-02/2004-02在天津大学生物医学工程实验室及天津医科大学电镜中心完成,25只Wistar大鼠和5只家猫由天津医科大学实验动物中心提供。干预:将25只Wister大鼠,随机分为5组,4个实验组和1个对照组,每组5只大鼠。实验1～4组接受调制脉冲磁场刺激,但各组作用时间及调制频率变化规律不同。实验1组接受α节律(10Hz)调制脉冲磁场刺激;实验2组接受β节律(20Hz)调制脉冲磁场刺激;实验3组采用先α节律后β节律波刺激;实验4组采用先β节律后α节律波刺激。记录大鼠记忆再现能力和脑内神经递质的变化。5只家猫先采用先α节律后β节律的脉冲磁场作用20min,比较磁场作用前后家猫的脑电节律的变化。主要观察指标:①采用改良“十”字迷宫法测试大鼠长时空间记忆再现能力的变化。②用高效液相色谱仪检测磁场作用后大鼠脑海马神经递质。③利用多导生理记录仪记录家猫脑电功率的变化。结果:25只Wistar大鼠和5只家猫均进入结果分析。①大鼠记忆再现能力比较:弱磁场刺激后5h实验2组、4组明显高于对照组犤(11.81±2.80,16.39±3.09,5.77±2.41)s,(P<0.05,P<0.01)犦。②大鼠脑海马多巴胺含量:实验组明显高于对照组犤(192.72±18.66,148.17±24.52)ng/g,(P<0.05)犦。③家猫β节律变化功率变化:脑电β频率段在功率谱中的面积百分比与刺激前相比显著增加(23.0±3.4,14.2±1.3)%。结论:大多数模拟脑电节律的弱磁场作用明显降低大鼠长时记忆再现能力,但特殊节律的弱磁场可能会提高大鼠记忆再现能力。这些影响与受钙离子内流及突触小泡调控的海马神经递质释放有关。

BACKGROUND： Recently, many researches suggest that transcranial magnetic stimulation has effect on learning and memory. Moreover, the effects of magnetic fields simulating electroencephalogram （EEG） rhythm on memory have been investigated. OBJECTIVE： To explore the effect of magnetic field simulating EEG rhythm on memory retrieval ability and its mechanism. DESIGN： Randomized controlled study. SETTING： Department of Medical lmaging, Tianjin Medical University, and School of Precision Instrument ＆ Photoelectronie Engineering, Tianjin University. MATERIALS： The experiment was conducted at the Electroscopic Center of Tianjin Medical University and Laboratory of Biomedical Engineering Department of Tianjin University from February 2002 to February 2004. Totally 25 Wistar rats and 5 domestic cats were selected from the Experimental Animal Center of Tianjin Medical University. INTERVENTIONS： All the 25 Wister rats were randomly divided into 5 group, 4 experimental groups and one control group with 5 rats in each group. Magnetic field simulating EEG rhythm was used to stimulate Wistar rats in the 4 experimental groups, but the time and frequency rate were different. Group 1 was stimulated by weak magnetic field with frequency in α rhythm （10 Hz）; Group 2 was stimulated by weak magnetic field with frequency in β rhythm （20 Hz）; Group 3 was stimulated by weak magnetic field with frequency changing from α to β rhythm; and Group 4 was stimulated by weak magnetic field with frequency changing from β toα rhythm. Memory retrieval ability and changes of neurotransmitters in the brain were reeorded. Five cats were treated with weak magnetic field with frequency changing from α to β rhythm for 20 minutes, and the changes of EEG power spectra before and after stimulation were compared. MAIN OUTCOME MEASURES： ① Retrieval ability of spatial information from long-term memory was tested with modified cross maze; ② content of neurotransmitters after magnetic field stimulation in hippoeampus of the rats was measured with high performance liquid chromatography; ③ changes of EEG power in the cats were recorded with multiple-channel electrophysiological recording device. RESULTS： Totally 25 Wister rats and 5 cats entered the final analysis. Comparison of memory retrieval ability： Memory retrieval ability in Group 2 and Group 4 was obviously higher than that in control group 5 hours after simulation [（11.81±2.80, 16.39±3.09, 5.77±2.41） s, P〈 0.05, P〈0.01]. Contentofdopamine （DA） in rats＇ cerebral hippocampus： It was obviously higher in the 4 experimental groups than in control group [（192.72±18.66, 148.17±9432） ng/g, P〈0.05].③Changes of arhythm power： The area percentage of power spectrum of β rhythm was increased after stimulation [（23.0±3.4, 14.2±1.3） %.]. CONCLUSION： Most of the weak magnetic fields simulating EEG rhythm of human brain can decrease the retrieval of long-term memory, but magnetic fieht with special rhythm may increase memory retrieval ability. All the effects are related to the release of hippocampal neurotransmitters which is mediated by the change of intracellular calcium （[Ca^2＋]i） and synaptie vesicle.