Central Alpha Bicoherence Is Reduced in Photosensitive Subjects

The photic driving response is known to induce epileptiform activity in photosensitive subjects and a recent hypothesis suggests that a reduced inhibitory effect of the alpha oscillations may be associated to this phenomenon. In this work, we studied the linear and non-linear spectral characteristic of the physiological alpha rhythms during a visual stimulation protocol in a group of twelve healthy and eight treated photosensitive subjects. Results confirmed the desynchronization of the individual alpha power during stimulation over the occipital region in both the groups and over the central for the PS subjects. A reduced bicoherence of the central alpha rhythm in PS subjects was found, suggesting the presence of a different behavior in the cortical structures involved in the generation of the alpha oscillations, both at rest and during visual stimulation.