Computer simulation and tank experimental verification of concentric ring electrodes

Brain activity generates electrical potentials that are spatio-temporal in nature. EEG is the least costly and most widely used non-invasive technique for diagnosing many problems related to the brain. It has very good temporal resolution, but does not poses high spatial resolution primarily due to the blurring affects of the volume conductor. The surface Laplacian enhances the spatial resolution and selectivity of the surface electrical activity as it takes the second spatial derivative of the potential. In an attempt to increase the localization and spatial selectivity a five point finite difference method has recently been used in a bipolar electrode configuration. Here we report on a nine point finite difference method as a model for the tripolar electrode configuration. We have designed a computer simulation to model electrode properties and a dipole at various depths below the electrode surface. A tank experimental was setup to verify the computer simulated potentials. In the simulation and tank experiment, a concentric ring electrode of 2 cm diameter was used. We found that the tripolar electrode configuration has significantly better localization and signal to noise ratio than the bipolar and quasi-bipolar configurations.