Analysis of the Effect of Variation of Reference Channel on Neuronal Activity for Motor Imagery Electroencephalography Signal

Objectives: Topographic map has been studied to observe the amount of neuronal activity at various electrode locations. Methods/Statistical Analysis: Electroencephalography (EEG) refers to recording of electrical activities (potential or current density) produced by neurons. A raw EEG signal obtained through electrodes placed in a specific pattern on the scalp. One of the electrodes needs to be selected as a Reference, relative to which electrical activity at all other electrodes shall be measured. It is usually said that electrodes at “inactive” regions of the scalp should be selected as the reference but this paper deals with analyzing what happens if any other electrode is selected as reference as there is no single best reference for all the purposes. The magnitude of electrical activity at various electrodes is indicated by color codes so that it is visually distinguishable. Findings: The difference in topography of EEG rhythms shall be observed and the extent up to which this is correct with different electrodes as reference would be seen. We observe that asymmetry arises if electrodes are at right or left rather than at Center line. We also observe that the electrodes which are at similar potential as that of the reference is indicated by Red color. Application/Improvements: The electrodes at very high potential than the reference are indicated by yellow whereas blue indicates medium activity w.r.t. the reference. These signals may be used for BCI application.