Study On Electroencephalic Alpha Rhythm

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.