Research On Dipole Source Locolization Of Brain Wave

The inverse problem or the source localization problem of brain wave which is oriented to find out the source in the brain based on EEG recorded from scalp is of great significance in both neuroscience research and clinical application.The development of the inverse problem of brain wave was investigated firstly. The two main methods were compared:cortical imaging technique (CIT) and low resolution electromagnetic tomography (LORETA). The current trends of this field is to acquire the current density of dipole distribution rather than a few dipoles . Based upon that,a new model was proposed-dipole layer localization method (DLLM):spherical dipole layer was used as source model,on which dipoles were distributed by equilateral triangles;three concentric inhomogeneous sphere was used as head model,which contains scalp,skull and cortex with different conductance. The dipole distribution and scalp potential tomography were obtained with singular value decomposition (SVD). Three dimensional imaging was also realized.In the simulation study,the parameters of dipoles were given,it would be considered whether it could be recovered correctly by DLLM based on scalp potential sampling with a set of electrode array. It was also examined that how electrode number influenced the recovered quality of dipole parameters.The simulation showed that the number,position and strength of dipole set were greatly close to the original condition;the shallower the dipoles were,the higher the precision of source localization was;the optimal depth of dipole layer was greatly close to the ideal position;the accuracy ofsource localization was increasing when more electrodes were used. The above result of the simulation suggests that this model is effective.The event-related potential (ERP) of 29 channels were analyzed with DLLM. The result were compared before and after special filter (Hjorth transformation). The acquired dipole distribution reflects different cognitive process.