Field mapping of EEG by unbiased polynomial interpolation.

The technique for field mapping of EEG using interpolation by an unbiased estimator of two-dimensional isotropic higher-order polynomial is developed. Assuming that the observed EEG contains noise, this method permits free positioning of the electrodes and does not reveal artificial oscillations as large as those of the Gibbs' phenomenon as in the case of the widely used Fourier interpolation. In the example of RMS (root mean square) amplitude at anesthesia, the onset of the fast activities began to appear clearly in the frontal and occipital area. By this method, not only RMS amplitude, but also instantaneous amplitude, such as visual evoked potential and somatosensory evoked potential, can be mapped.