Quantification of abnormal coordination of brain activity during an auditory task in epilepsy

Brain electrical activity acquired under cognitive paradigms is quantified using several different methods. To compare the elicited response to an auditory oddball task between normal subjects and a group of refractory epilepsy patients, event-related synchronization/ desynchronization (ERS/ERD) was analyzed in this study. Our objective is to test whether such a quantitative parameter can be a feature to distinguish the epilepsy group from the healthy controls, and thus examine its possible use for diagnosis and therapy evaluation purposes. Hence, we investigated ERS/ERD in standard electroencephalographic (EEC) frequency bands for target and non-target stimuli in both groups. According to our results, several differences between the responses of the two groups are observed in the theta band. The main distinction is that in the control group large amplitudes of non-phase-locked theta activity occurred, which is more pronounced in the frontal midline electrode positions, as response to both stimuli, whereas in the patient group this activity was not observed. Thus, we conclude that ERS/ERD in the theta band can be used as a quantitative parameter for diagnosis and therapy evaluation in epilepsy.