EEG-fMRI measures of functional brain connectivity in epilepsy

A study of the epileptic seizure dynamics using simultaneous recording of electroencephalography correlated functional magnetic resonance imaging (EEG-fMRI) data from 5 focal epilepsy patients undergoing pre-surgical evaluation was realised with the aim of identifying the focus and propagation network seizure-involved. A method based on the General Linear Model (GLM) at different neurophysiology regressor lags (LasgM), a connectivity model-based method, Dynamic Causal Modelling (DCM), and a data-driven method, Granger Causality (GC) were investigated. DCM analysis provided meaningful and significant results when a sufficient number of seizure events was recorded, but suffered from the generally poor data signal-to-noise ratio (SNR). The concordance between the LagsM results and the clinical expectation suggests that LagsM can be useful as a complementary approach. Intending to establish the validity of a GC approach for the problem addressed, a simulation study was performed and the results showed that it is not appropriated.