Why Some Images Trigger Seizures

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In people with photosensitive epilepsy, flashing lights are well known for their potential to trigger seizures. The results can be quite stunning. For instance, a particular episode of Pokémon sent 685 people in Japan to the hospital. But seizures can be triggered by certain still images, too. Now, researchers reporting in Current Biology on May 8 who have conducted an extensive review of the scientific literature think they know what it is about some static pictures that can trigger seizures.

The key, they propose, is a particular repetitive pattern of neural activity in the brain known as gamma oscillations that occurs when people view certain images, such as black and white bar patterns, and not others. In fact, the researchers say, it’s possible that those kinds of images are responsible for other problems, such as migraine headaches, particularly in people who are generally sensitive to light.

“Our findings imply that in designing buildings, it may be important to avoid the types of visual patterns that can activate this circuit and cause discomfort, migraines, or seizures,” says Dora Hermes of the University Medical Center (UMC) Utrecht in the Netherlands. “Even perfectly healthy people may feel modest discomfort from the images that are most likely to trigger seizures in photosensitive epilepsy.”