Uncomfortable sight from an ancient reflex of the eye
Reflexive system of the human eye also produces a conscious visua
The eyes are for seeing, but they have other important biological functions, including automatic visual reflexes that go on without awareness. The reflexive system of the human eye also produces a conscious, visual experience, according to a new study from researchers in the Perelman School of Medicine and School of Arts and Sciences at the University of Pennsylvania. The findings, reported today in the Proceedings of the National Academy of Sciences, may provide insight into the excessive light sensitivity sometimes experienced by people with eye disease, migraine headaches and concussions.
The study addressed the properties of melanopsin, a blue-light sensitive protein in the eye that establishes the rhythm of the day-night cycle and the familiar constriction of the pupil to bright light. The researchers created a special pulse of light that stimulates only the melanopsin cells of the eye. They showed this light pulse to people and measured their pupil response and brain activity, as well as asked them what they saw. Remarkably, they found that people have brain activity and a visual experience in response to a light that is invisible to the parts of the eye normally used for seeing.