Study Of The Reference Independent Techniques

Electroencephalogram (EEG) is an important tool for the study of human brain. EEG may provide the information of the electrophysiological activity of the human brain by measuring the electromagnetic field on the head surface, which is resulted from the neural active in the brain. EEG can help people to discover the secret of human brain. As the effect of an active reference is unavoidable in EEG practice, it is important to study the reference independent techniques.Based on the boundary element method (BEM) and a realistic head model, investigated are the reference electrode standardization technique (REST), moderate scale Laplacian of high-resolution EEG, based on spline function or radial-basis function, and high order difference approximation of surface Laplacian. Both REST and Laplacian are belonging to reference independent techniques.The details and results are shown as follows1) Reference electrode standardization techniqueTo solve the problem of the effect of an active reference in EEG recording, the reference electrode standardization technique was studied for a realistic head model, REST is based on the equivalent distributed source model to obtain the potentials with a reference at infinity from the potentials with a scalp point reference or with the average reference. Both simulation results and real human visual evoked potential data confirmed the effect of REST.2) Moderate scale LaplacianThere are generally two categories of the Laplacian estimate. One is the local approach and the other is the global approach. Both the local and global approaches have their own advantages and disadvantages.