Spectral and Coherence Analysis of EEG during Intermittent Photic Stimulation in Patients with Photosensitive Epilepsy, International Journal of Bioelectromagnetism,

Objective: The aim of this study is to assess changes in the EEG dynamics preceding the transition to the photo-paroxismal response (PPR) in photosensitive patients Methods: Occipital EEG derivations were considered in 10 photosensitive patients and 10 controls, both at rest and during intermittent photic stimulation (IPS) at 14, 3, 5, 10, 20 and 40 Hz. The two EEG signals were analysed by means of an autoregressive (AR) bivariate parametric model, and the correspondent autospectra and coherence function were qualitatively and quantitatively assessed. Results: At rest, the coherence function showed an higher number of peaks in the patients compare with the controls, mostly in the gamma band. Also, during IPS at 14 at 10 Hz, where stimulus was more effective in producing PPR, high frequency iper-synchronization in the patients group was enhanced before the appearance of the paroxysmal response. The same did not happen at those frequencies not able to bring about to PPR Conclusion: Results indicate an increased synchronization, mostly in beta and gamma bands, present at those frequencies able to sustain paroxysmal responses.