Bispectral analysis of EEG during non-convulsive seizures

In this research, the normalized third order spectrum called the bi-coherence has been utilized to study the quadratic phase coupling (a manifestation of non-linearity) in 3 epileptic patients. Simple statistical features of the bi-coherence in the principal domain of the bi-frequency plane and in each of the combination of different frequency band (example: delta-delta, theta-gamma etc.) in the bi-frequency plane were calculated. All the features were then ranked according to the area under curve (AUC) of the ROC curve. The best nine features were used for both subject dependent and subject independent classification. The subject independent classification, using a linear classifier, trained with three seizures (data belonging to patient 1) yielded 100% detection of the two test seizures (data belonging to patient 2) with a latency of 7 and 5 seconds respectively and specificity of 89.33%.