Case report: responses to stripe width changes and to complex gratings of a patient with pattern-sensitive epilepsy

A pattern-sensitive subject's ability to see faint gratings of several different stripe widths (spatial frequencies) was essentially normal, with the greatest sensitivity occurring for gratings with 2 cycles of light and dark stripes per degree of visual arc (c/deg). Epileptiform discharges, however, occurred maximally at a narrower stripe width, 5 c/deg. The 50% bandwidth of the epileptic response was approximately one octave, which is similar to postulated 'spatial frequency channels' in the visual system. Hypothesized inhibitory interactions between the 5 c/deg grating and a 15 c/deg grating were not observed.