| Theme |
Functional and Organic Changes of Brain Observed in Dialysis Patients |
| Title |
The methods for analyzing the evoked potential |
| Author |
Yoshiaki Takanashi |
Department of Neurology and Geriatrics, Institute for Neurological Diseases and Gerontology, Kyoto Prefectural University of Medicine |
| Author |
Keisuke Toyama |
Department of Physiology, Kyoto Prefectural University of Medicine |
| [ Summary ] |
The most important aim of measuring cerebral evoked potentials is to identify the localization of the generator sources of different kinds of evoked potentials. We reviewed two methods of identifying generator sources, i.e., 1) current source density analysis (CSD) and 2) dipole tracing methods (DT). CSD is a method of determining source localization from the distribution of potentials, and is advantageous in that little attention is required for the reference electrodes. This CSD mapping is based on computation with the Laplaciean equation, recognized as an operator subtracting the average potential in the vicinity of the potential at any given point. However, this method has not often been applied in the clinical setting, since it requires complicated computation from measured potentials and a large number of electrodes. The DT method is based on the measurement of a 3-dimensional head model and localization of a single or two equivalent current dipoles using the method of least squares of the difference between the potential recorded from the scalp and that calculated from the equivalent current dipoles. The DT method reviewed here in has an advantage in that the difference in conductivity between the surfaces, including those of the scalp, skull and brain, can be taken into account in estimating the dipole location. |