ipRGCs

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Studies on migraine headaches, which are often exacerbated by bright lights, are revealing another role of ipRGCs in the human brain. Harvard headache researcher Rodrigo Noseda had observed that light could trigger migraines even in blind people; he therefore theorized that the headaches might be triggered by ipRGCs. To explore the idea, he dissected the brains of rats, staining both ipRGCs and pain-signaling neurons to trace their paths.The ipRGCs connect to pain neurons in the thalamus, he found, suggesting that exposure to light could disturb pain-signaling neurons as well. Light sensitivity can be devastating for some migraine sufferers. They can’t drive, write, or even read. Once researchers understand the pathway well enough to manipulate it pharmacologically, such patients might find relief.

Unfortunately, switching off the ipRGCs entirely is not a viable option. These neurons are now known to extend into the thalamus, a region of the brain known for promoting awareness. Presumably they deliver some kind of essential information there. When neuroscientists find out what kind of message it is, they will make real progress—perhaps toward fighting pain, and definitely toward getting a better look at our secret selves.