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When people suffer from a migraine, they often retire to a cave-like dark room. But exactly why does bright light hurt the migraine sufferer? A possible answer was published this week in the online issue of journal Nature Neuroscience. A big clue was that even some of the blind migraine victims avoid light.

Migraine pain is thought to come from irritation¹ of the meninges, membranes² around the brain and central nervous system. So researchers took two groups of blind migraine sufferers. One group was totally blind. The other group was legally blind but could still make out light and dark.

The totally blind group did not suffer from what's called photophobia. But light did aggravate³ the migraines of the legally blind group. Researchers thus suspected a group of light-sensing retinal cells that help regulate sleeping and waking, because these are the only active light receptors in the legally blind group.

Working with animals, the investigators⁴ discovered that those retinal cells send signals through the optic nerve to the brain—and to a specific group of neurons that are kicked into action during a migraine. The scientists hope the findings lead to therapies that can give migraine sufferers a brighter future.

—Cynthia Graber