Nature Neurosci. doi:10.1038/nn.2475 (2010)

For many migraine sufferers, light makes the pain worse. Rami Burstein of Harvard Medical School in Boston, Massachusetts, and his colleagues began their quest to figure out the neural mechanism behind this by studying 20 blind migraine sufferers. Those who could detect light reported heightened pain when exposed to it.

The researchers then examined the posterior thalamus — the brain region containing neurons that fire during migraines — of anaesthetized rats. They found that projections from a specific group of retinal cells converge on other cells that process both migraine pain and light signals. Most of the retinal cells involved can respond to light but cannot form images and are still functional in some blind people.