TV can be bad for you: Three years ago some 700 Japanese children watching a Pokemon cartoon suffered epileptic seizures. Now scientists have discovered what sorts of visual patterns are so unnerving for children with photosensitive epilepsy (PSE). The findings could guide the development of safer video game and TV graphics.
The most common form of epilepsy, PSE afflicts as many as 0.8% of children aged 4 to 14. The number of diagnoses has risen in recent decades with the growing popularity of flashy video games, which can trigger a seizure. Most kids grow out of PSE by the time they're in their late teens. Although the condition has been recognized for years, no one has pinpointed what sorts of patterns are most dangerous or why.
Neurophysiologist Vittorio Porciatti of the Italian Research Council's Institute of Neurophysiology in Pisa and his team decided to find out. They showed TV screens with moving black-and-white stripes to 11 PSE sufferers and 13 control subjects, all of whom were adolescents or young adults. Meanwhile, scalp electrodes monitored brain activity. First the researchers varied the speed at which the stripes crossed the screen and found a frequency that stimulated the strongest response in all the subjects. Then they fiddled with the contrast between the stripes, which could range from shades of gray to stark extremes of black and white. As the researchers upped the contrast for control subjects, they saw that the brain activity increased and then leveled off. In young people with PSE, however, the brain signal kept intensifying, until the activity was twice as high as for the other group, they report in the March Nature Neuroscience.
The study, says neurophysiologist Colin Binnie at King's College London, "is the first to identify a physiological abnormality in PSE patients." What's more, adds epilepsy expert Dorotheé Kasteleijn-Nolst Trenité of the Dutch National Epilepsy Center in Heemstede, "this gives us an idea about the underlying mechanism of how epilepsy in general--not just PSE--works." Until video game manufacturers incorporate this new information, Porciatti advises kids to reduce the contrast on their monitors.