On Dec. 16, 1997, at exactly 6:50 p.m., 685 people in Japan, most of them children, simultaneously suffered epileptic seizures. When doctors around the country began looking into the cause of the outbreak, a surprising culprit emerged: Every one of the seizure victims, at the fateful hour, was watching the TV cartoon "Pocket Monsters."
Since 1997 we've known that "Pocket Monsters" caused the seizures. Now we know why. Japanese researchers have found evidence that the seizures were provoked by rapid changes of blue and red in the cartoon's color, and with this discovery, they believe they may have pinpointed a new type of epilepsy related to color sensitivity. Their report is published in the June issue of the journal Annals of Neurology.
Flickering lights -- strobe lights, for example -- can trigger epileptic seizures. Patients who experience such seizures are said to suffer from "photosensitive epilepsy." Rapid shifting between light and dark causes nerve cells in the brain to fire electrical impulses more rapidly than usual. In people with photosensitive epilepsy, the resulting havoc in the brain can lead to muscular convulsions or blackouts.
Something similar happened to the "Pocket Monsters" watchers. Dr. Shozo Tobimatsu, along with colleagues in the neurology department at Kyushu University in Japan, studied four boys who had suffered seizures during the cartoon. Like most of the other victims, they had never suffered from epilepsy prior to the "Pocket Monsters" episode, although two of the boys had a family history of epilepsy.
The researchers measured EEG responses as the boys watched the cartoon -- first in black and white, then color. Only two of the boys showed sensitivity to the black and white version, but all four boys experienced abnormal, epilepsy-like brain trouble when exposed to the color version. After further testing, Tobimatsu concluded that rapid color changes between blue and red in the cartoon were most significant in triggering the seizures.
In Britain in 1993, three viewers experienced seizures while watching a cartoon called "Pot Noodles." A 1998 report on those color-induced seizures revealed a sensitivity to rapid color changes similar to that experienced by the "Pocket Monsters" watchers. Based on the findings of both reports, the Japanese team is proposing a new subcategory of photosensitive epilepsy called "chromatic sensitive epilepsy."
Tobimatsu says, "Fortunately, this tragedy was only reported in Japan. The research committee of the Japanese Ministry of Health and Welfare estimated that about 10 percent of children have had visual symptoms or seizures," resulting from photosensitive epilepsy.
"Pocket Monsters" was yanked from Japanese TV after the seizure epidemic, but now it's back on the airwaves -- after editors ditched the offending episode and winnowed out all strobing segments from other episodes. The show now runs in syndication in the United States, too, on stations that carry children's programming. No further problems have been reported.
But it may not be the last time this kind of problem pops up. So should TV animators be held accountable for the health effects of their creations? "Sure, they need some regulations on TV animations," Tobimatsu says. "Before this episode, only the U.K. [had] such guidelines. Since this episode, Japanese TV companies have also prohibited the use of rapid color changes in the animation."
Cartoons aren't the only potential offenders, though. In 1991, American Dianne Neale suffered seizures when listening to the voice of "Entertainment Tonight" co-host Mary Hart. Neale suffered from a rare form of epilepsy called temporal lobe seizure, and the mere sound of Hart's electronically transmitted voice triggered abnormal discharges in her brain.
Further proof that mom was right: TV can be bad for you.