Form-similarity between phosphenes of adults and pre-school children's scribblings

WE reported earlier1,2 a method which permits reproducible electrical stimulation of phosphenes—that is subjective light patterns, visible with closed eyes—without surgery. It was shown that these patterns resembled line drawings of ‘geometrical’ forms, and that a great number of them could be stimulated within a rather small bandwidth (±10 per cent of the mean excitation frequency) within the electro-encephalographic frequency range. In the meantime, the dependence of this effect on the shape of the stimulating current3, the identification and lifetime of single phosphenes4 and the influence of hallucinogenic drugs on their shape5 have also been investigated. In addition, copies of 520 phosphenes observed by 313 subjects have been collected3: it was possible to classify these into 15 form groups (‘phosphene-Linnaeus’, 1–15, first two columns of Table 1).