Reflexive system of the human eye
Human eye are not only for seeing, and also have other important biological functions, including automatic visual reflexes.
According to a new study from the University of Pennsylvania, the reflexive system of the human eye produces a conscious, visual experience. The researchers said, the high light sensitivity sometimes experienced by people with eye disease, migraine headaches and concussions.
However, researchers created a special pulse of light that stimulates only the melanopsin cells, a blue-light sensitive protein in the eye.
Melanopsin is a part of our visual system, it controls several important biological responses to light, said, lead author, Manuel Spitschan. If we have a visual experience that assists these reflexes, as the normal light that stimulates melanopsin will also stimulate the cone cells of the eye.
To solve this problem, the researchers developed a special kind of light pulse that stimulates melanopsin, but is invisible to the cones. These lights switch between computer-designed “rainbows” of light.
For testing, researchers recorded people pupil response who watches these light pulses. They confirmed that the light pulse invisible to the cones brings a slow, reflexive constriction of the pupil. They then measured brain activity and found that the visual pathway of the brain answer to the melanopsin stimulus.
“This was a particularly exciting finding,” said senior author Geoffrey K. Aguirre, MD, PhD, an associate professor of Neurology at Penn. A neural response within the occipital cortex suggests that people have a conscious experience of melanopsin stimulation is explicitly visual.
The research work can understand the experience of people with photophobia. “Research on mice makes us think that melanopsin contributes to the sensation of discomfort from a very bright light,” Aguirre said.
The new study found the melanopsin stimulus causing discomfort, and people with photophobia may also experience a stronger form of this response to melanopsin. So, the new tool helps us to better understand the excessive light sensitivity.
More information: [PNAS]