It is well known that computerized EEG ＆ EP mapping systems improve the diagnosis of human brain disease. In addition, this system is a very important instrument to study the human cognitive process. In this paper, 12 channel computerized HBPMAS( Human Brain Potential Measurement and Analysis System ) has been developed for the basic research of human brain. The instrument consists of EEG-amplifier, Filter, A/D Converter, EEG-PC Interface, Stimulator and 3-Dimensional Digitizer. The analysis S/W is composed of FFT, Frequency Filtering, Evoked Potential Detection(using ensemble average method), Interpolation and so on. This system is expected to enable us to study the human brain function and improve the result of diagnosis.
The accurate localization of electrical sources in the brain is one of the most important tasks in EEG, especially in the analysis of evoked responses and of epileptiform spike activity. All kinds of the source localization method find the neuron activity on the assumption that equivalent current dipole is only one or two. However, we generally don't know about how many equivalent dipoles are created in the human brain.
This paper presents the theory and experiments of finding the functional region of human brain using single current dipole model for the neuron activity and concentric triple shell model for the head shape. A study of estimating the number of equivalent dipole based on measured potential itself using Laplacian operation is given. We found out that the Laplacian operation of theoretic human brain potential revealed the number of equivalent dipole, the solid angle and the radial polarity. To confirm this method, we calculate the Laplacian in the case of real experimental evoked potentials which are caused by visual and finger movement excitation. The similarities between estimated positions of neural excitation(visual and finger movement) and physiological brain function regions are verified.
