Hemifield Red Flicker Stimulation in a Patient with Pattern‐Sensitive Epilepsy

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Abstract
The provocative effects of paroxysmal discharges (PD) by lateral, upper and lower hemifield red flicker stimuli were studied in a 24 yr old female patient with pattern-sensitive epilepsy, who showed a generalized photoconvulsive response. In this patient fullfield red flicker stimulation provoked generalized PD, whereas hemifield red flicker stimuli showed different characteristics. Left hemifield red flicker stimulation provoked focal PD in the right posterior regions. Right hemifield red flicker stimulation was apparently less effective than the left in provoking focal posterior PD in the contralateral hemisphere. Lower hemifield red flicker stimulation provoked focal posterior PD that were slightly more pronounced over the right side. No definite PD were provoked by upper hemifield red flicker stimulation. Red flicker from the left lower quadrant of the visual field may be the most potent stimulus in provoking focal posterior PD. The right occipital lobe may be more sensitive to red flicker stimulation than the left occipital lobe. In consideration of the retinotopic projection from the left lower quadrant of the visual field onto the visual cortex, the right upper lip of the visual cortex is presumed to be the most sensitive to red flicker stimulation. Hemifield red flicker stimuli might be useful for EEG examination of the visual cortex in patients with photosensitive epilepsy, who are particularly sensitive to red flicker stimulation.

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