Pattern‐Sensitive Epilepsy. I: A Demonstration of a Spatial Frequency Selective Epileptic Response to Gratings

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Abstract
Rare individuals suffer epileptic seizures when they view certain images, particularly stripes. Contrast-threshold functions (the ability to see faint stripes of various widths) were determined for 2 pattern-sensitive brothers, and the epileptogenicity of various patterns was assessed for 1 of them. Since wave grating contrast-detection thresholds for the 2 subjects were essentially normal, with lowest thresholds at approximately 2 cycles/degree (c/deg). Epileptiform discharges occurred maximally at 5 c/deg with a 1-octave 50% bandwidth. Pattern epileptogenicity was increased by the addition of a 3rd harmonic sine wave grating to its fundamental, but was unaffected by the phase relation of the 2 gratings. The frequency selectivity of epileptic responsiveness was quantitatively similar to a spatial frequency channel. Inhibitory interactions were not present. Relations are suggested between the phenomena of pattern-sensitive epilepsy and hypothesized spatial frequency channels.