【作者】 熊红川；

【导师】 尧德中；

【作者基本信息】 电子科技大学 ， 生物医学工程， 2010， 博士

【摘要】 脑电信号的节律性在介观和宏观尺度上都有明显的表现。不同节律的脑电在脑功能中被认为具有不同的作用。越来越多的研究表明,由于大脑的极端复杂性和内部系统间的相互作用,即使是在最简单的脑功能作用时,不同节律也存在复杂的变化。本文着重研究了其中alpha节律的相关问题,从理论模型、行波、成像、MRI直接检测等多个方面考察研究alpha节律。主要内容如下:1.利用脑电皮层丘脑模型(corticothalamic model),对脑电功率谱密度进行了仿真,考察了alpha波谱峰分裂现象,认为模型中神经冲动传导的非均匀延时是产生alpha节律功率密度谱分裂的基础,而皮层与丘脑间的反馈连接的强度变化则是分裂现象只在少数人中观测到的重要原因。2.利用脑电质心的概念,研究了alpha节律的行波现象。对alpha行波的轨迹进行了研究。考察了滤波对轨迹的影响。提出了质心极值(extrium points of center of mass)的概念。其分布总是出现在枕区和前额区。这个结果较好地描述了alpha波的空间分布特性。3.计算了不同参考电极对脑电电位“质心”计算的影响。用仿真和实际数据计算比较了平均参考、连接耳参考、头顶参考和近期出现的近似零参考技术REST(reference electrode standardization technique),结果表明,采用REST可使得电位“质心”的计算误差在多数情况下更小。说明在进行“质心”等与脑电波形相关的计算的时候,采用近似的零参考技术可以获得更真实的结果。4.利用脑电质心概念,发展了脑电质心分布概率密度成像方法,并提出用梯度和标准差对此种图像均匀性进行分析和评估。将该成像方法应用于睁闭眼状态下的脑电alpha频段,其均匀性分析和分区统计能很好地刻画alpha波阻塞现象,表明该方法是一种可行的脑电分析手段,为脑电分析提供了一种新的途径。5.用理论仿真的方法研究了树突电流模型的神经活动磁场(neuronal magnetic field,NMF),并测算相关神经磁场利用磁共振成像(magnetic resonance imaging, MRI)方法直接检测的可能性;设计了用nc-MRI(neuronal current MRI)检测EEG中alpha波活动的实验,即利用睁眼阻断alpha波的现象,探讨用nc-MRI信号检测alpha波的可行性。结果表明,所得MR信号在alpha频段有明显的变化,且主要在alpha活动明显的枕区有比较一致的变化,从而初步证明了在特定的条件下,应用nc-MRI检测神经电流活动信号是可能的。更多还原

【Abstract】 EEG rhythm exists in the meso-and macro-scale. EEG with different rhythms was considered to be of different brain functions. More and more studies have shown that the extreme complex internal interactions result in different rhythms with complicated changes, even in the simplest role of brain function.This dissertation focuses on studies of the alpha rhythm and the relevant issues, such as its theoretical model, traveling wave, imaging, MRI direct detection, etc. The main contents are as follows:1. Simulation study of the EEG power spectral density has been carried out under the EEG corticothalamic model to research alpha-wave splitting phenomenon. We put forward that the non-uniform delay of the nerve impulse conduction in this model is the basis of division of the alpha rhythm density spectra, and that the intensity change of the feedback connections between cortex and thalamus results in such phenomenon that the splitting occurs only among a few persons.2. A research of the traveling waves of alpha rhythm by means the EEG mass center. Through the research of the tracks of the alpha traveling waves, the impact of the filtering on the tracks was analyzed. And then we put forward a concept“Extrium Points of Center of Mass”, which is distributed in the occipital area and the prefrontal cortex, and such result just illustrates the typical feature of spatial distribution of alpha waves.3. An analysis of the impact of different reference electrodes on the calculation of EEG mass center. We compared the average reference, linked mastoids reference, the vertex reference and the lately developed infinity reference (REST:reference electrode standardization technique) with simulated and real data. The results show that the application of REST can reduce the calculation errors of mass center of the potential in many cases. It proves that the application of the approximate neutral reference (REST) can make the result closer to the truth in the calculation of mass center and other EEG waveform related analysis.4. Based upon the concept of EEG mass center, we developed a new imaging technique based on the probability density distribution of the EEG mass center, and further provided two evaluation indexes of the image uniformity: gradient and standard deviation of the imaging map. This imaging technique is applied to the analysis of the EEG alpha frequency band with eye opened and eye closed. The uniformity analysis and subarea statistic can successfully interpret the phenomenon that alpha rhythm was blocked. The results prove the feasibility of this new EEG-analysis technique.5. Based upon a theoretic simulation model, we investigated the NMF (neuronal magnetic field) of a dendrite current model, and tested the possibility of the direct detection of the neural magnetic field by MRI (magnetic resonance imaging). We designed an nc-MRI (neural current MRI) experiment to test the phenomenon that alpha rhythm was blocked with eye opened. The results show that there are obvious changes of MR signals in alpha frequency band, and such changes mainly occur in regions of alpha activity. Such results prove the feasibility of applying nc-MRI to test or detect the neural current signals.更多还原