Altered cortical synchronization in photosensitive idiopathic generalized epilepsy
Alessandro Benedetto, Cecilia Steinwurzel, Francesco Turco, Enrica Bonanni, Roberto Cantello, Gionata StrigaroAbstract
Objective
To characterize cortical excitability and synchronization dynamics in patients with idiopathic generalized epilepsy (IGE) and photosensitivity by assessing steady‐state visual evoked potentials (SSVEPs) elicited by intermittent photic stimulation.
Methods
SSVEPs were recorded from the occipital cortex (Oz) in patients with IGE and photoparoxysmal response and in age‐matched healthy subjects (HSs) during stimulation at 8 and 16 Hz, with eyes open and closed. We analyzed evoked (phase‐locked) and induced (non–phase‐locked) responses, inter‐trial phase clustering (ITPC), broadband electroencephalographic energy, and resting‐state spectral and alpha‐peak dynamics.
Results
Compared with HSs, patients showed consistently greater electroencephalographic energy at stimulation frequencies and across the broadband spectrum, particularly for induced SSVEP responses. Despite this increased amplitude, patients exhibited reduced phase coherence, reflected by significantly lower ITPC across all conditions. Resting‐state analyses revealed heightened broadband power but unstable alpha oscillations, with greater variability in individual alpha‐peak frequency. Together these findings indicate enhanced cortical responsiveness accompanied by impaired temporal precision in neural synchronization.
Significance
Photosensitive IGE is characterized not only by exaggerated visual cortical excitability but also by disrupted synchronization dynamics, suggesting a state of strong but temporally unstable neural activity that may facilitate transitions toward photically induced paroxysms. SSVEP‐based measures and alpha‐variability metrics may serve as functional biomarkers of network instability in photosensitive epilepsy.