Normalized Mutual Information in Phantom Model and Human Electroencephalogram Data for Emulation of Conventional Disc Electrode via the Outer Ring of Tripolar Concentric Ring Electrode

With some of the noninvasive electrophysiological measurement applications benefiting from simultaneous collection of data via both conventional disc electrodes and concentric ring electrodes, an emulation of the former by the outer ring of the latter was previously proposed and has since been used widely. Its effectiveness was validated using linear time and frequency domain signal synchrony measures (cross-correlation and coherence respectively) on both phantom model data and resting electroencephalogram from six healthy human subjects. However, application of a nonlinear signal synchrony measure (normalized mutual information) in this study resulted in mean values of less than 0.7 on both phantom model and human electroencephalogram datasets indicating that the outer ring of a tripolar concentric ring electrode may not be as suitable as an emulation of the disc electrode as previously suggested. Therefore, alternative options like the central disc or the middle ring will need to be assessed in the future work.