Pokemon on the Brain
March 11, 2000 Pokemon is the popular Japanese cartoon show that has swept across the world. Is watching Pokemon dangerous to your health? In 1997, one episode caused some serious problems for viewers in Japan and now scientists have an idea why.

Pokemon (episode #38) Packs a Punch On the evening of December 16, 1997, millions of people all over Japan gathered in their homes to watch Pokemon (episode #38). About 20 minutes into the program there was a scene of a rocket explosion that flashed red and blue lights at a rate of about 12 times per second. This explosion scene was mixed with about five seconds of flashing lights from the eyes of "Pikachu," a popular Pokemon character. Suddenly, viewers started to complain of blurred vision, headaches, dizziness and nausea. Some people even had seizures, convulsions and lost consciousness. A total of 685 children (310 boys, 375 girls) were taken to hospitals by ambulances. Although many children recovered during the ambulance trip, more than 150 of them were admitted to hospitals. Two people stayed in the hospital for over 2 weeks!

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The Cause and Solution Scientists believe that the flashing lights triggered "photosensitive seizures" in which visual stimuli such as flashing lights can cause altered consciousness. Although scientists know that approximately 1 in 4000 people (0.5 - 0.8% of children between 4-14 years old) are susceptible to these types of seizures, the number of people affected by this Pokemon episode was unprecedented. Soon after this unfortunate incident, Japanese television broadcasters and medical officials got together to find ways to make sure this never happened again. They established the following guidelines for future animated programs: Flashing images, especially those with red, should not flicker faster than three times per second. If the image does not have red, it still should not flicker faster than five times per second. Flashing images should be displayed for a total duration of less than two seconds. Stripes, whorls and concentric circles should not take up a large part of a TV screen. New Experiments from Italy Italian scientists have detailed an abnormal brain response to flashing lights in people who suffer from photosensitive seizures. For both normal volunteers (average age, 15.2 years) and photosensitive volunteers (average age, 18 years), they examined the brain's electrical response to changing light patterns. The researchers found that in normal volunteers, as the flickering lights increased in contrast, the response of the brain increased. At high contrast levels, the brain's response leveled out. The brain response in photosensitive people also increased with higher contrasts, but it did not level out at the highest contrast levels (see figure on the right; data adapted from Porciatti et al., 2000). This was especially apparent when the lights flashed at rates between 4 and 10 times per second. The scientists believe that the brains of photosensitive people have a defective or absent mechanism that controls the reaction to visual information. This may have caused the seizures associated with the Pokemon episode (#38).

If you have absolutely no idea what Pokemon is all about, visit the official Pokemon Web Site.

References and further information: Enoki, H., et al., Photosensitive fits elicited by TV animation: An electroencephalographic study, Acta Paediatrica Japonica, 40:626-630, 1998. Ishida, S., et al., Photosensitive seizures provoked while viewing "Pocket Monsters," a made-for-television animation program in Japan, Epilepsia, 39:1340-1344, 1998. Niijima, S-I., et al., Clinical electroencephalographic study of nine pediatric patients with convulsion induced by the TV animation, Pocket Monster, Acta Paediatrica Japonica, 40:544-549, 1998. Porciatti, V. et al., Lack of cortical contrast gain control in human photosensitive epilepsy, Nature Neuroscience, 3:259-263, 2000. Takada, H., et al., Epileptic seizures induced by animated cartoon, "Pocket Monster," Epilepsia, 40:997-1002, 1999. Takahashi, T. and Tsukahara, Y., Pocket Monster incident and low luminance visual stimuli: Special reference to deep red flicker stimulation, Acta Paediatrica Japonica, 40:631-637, 1998. CNN report - 12/17/1997