Estimation of photoparoxysmal response elicited by half-field visual stimulation.

We examined photoparoxysmal responses (PPRs) elicited by half-field visual stimulation with deep-red flicker light to determine the neurophysiological features of photosensitive epilepsy (PSE). EEG revealed two types of PPRs. One had the focal spike in the occipital region and the other in the temporo-occipital region at the contralateral hemisphere. The equivalent current dipoles of these types were located at the occipital cortex and the inferior temporal (IT) cortex, respectively. These cortices comprise one of the main pathways in the visual system, and they play important roles in color discrimination. Thus, we propose that the visual system, especially the occipital cortex and the IT cortex, might be involved in the generator mechanism of PSE.