If you are someone like me who suffers with Migraine headaches then you would understand this research better. Every time I have the horrible headache, I shut myself down in dark room and wait for the medicine to work. Finally scientists have a better idea on why bright light affects migraine.
The article “A neural mechanism for exacerbation of headache by light” by Rodrigo Noseda, Vanessa Kainz, Moshe Jakubowski, Joshua J Gooley, Clifford B Saper, Kathleen Digre & Rami Burstein published in Nature Neuroscience sheds light on the reasoning. Read the article here.
The article talks about the study on two groups of blind people migraine sufferers – one completely blind and the other legally blind but still perceptive to light/dark. Interestingly, the totally blind group did not suffer from what’s called photophobia. But light did aggravate 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 investigators 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. (from here)
The patients in the first group, who couldn’t sense light, showed no worsening of their headaches when exposed to light. Those in the second group described increased pain in light.
“This suggested to us that the mechanism of photophobia must involve the optic nerve, because in totally blind individuals, the optic nerve does not carry light signals to the brain,” Burstein said.
The scientists knew that the second group of blind individuals didn’t maintain normal sleep-wake cycles, which are dictated by light, while the other group did. So perhaps, they thought, retinal cells that control biological functions like sleep and wakefulness are involved in this light-headache phenomenon. These retinal cells contain melanopsin.
They tested out these ideas in a lab, by injecting dyes into the eyes of rats with migraine headaches. By following the dyes, the researchers traced the path of the melanopsin retinal cells through the optic nerve to the brain, where they found a group of brain cells that became electrically active during migraines.
“When small electrodes were inserted into these ‘migraine neurons,’ we discovered that light was triggering a flow of electrical signals that was converging on these very cells,” Burstein said. “This increased their activity within seconds.”
And even when the light was removed, Burstein said, these neurons remained activated. “This helps explain why patients say that their headache intensifies within seconds after exposure to light, and improves 20 to 30 minutes after being in the dark.”Source: www.foxnews.com
Hopefully, this study will help future researchers to understand Migraine better and maybe one day eradicate it from human sufferings.