Do you know why your vision is the sharpest in twilight and dawn?

If you have ever been awake in the dawn of a dawn or are still out there when it is dusk, you may have noticed that your vision is sharper than usual

A German study says this is because your brain changes the way in which it interprets the visual signals of sunrise and sunset, according to an article in New Scientist magazine.

The author of the study, Christian Kell, explained that our brain always works in the background. But when it comes to dawn or dusk, this continuous background activity moves into a visual cortex, a part of the brain that interprets visual information.

Thanks to this noise reduction in the signal and background ratio, the human visual cortex can focus on the perception of poorly lit environments and objects. So we could see it better despite the low light level at that time.

"Your brain is becoming more sensitive. A weak signal comes in that will have a higher signal and noise ratio, "explains Kell, a neuroscientist at the Goethe University.

He and his colleagues determined this with an experiment with 14 men. They asked participants to watch a mildly bright orange cross on a black background at different times of the day. They reported that the participants had the most success in their task at 8 am and 8 pm.

Ancient people should improve their vision during the dawn and dusk in order to avoid predators

The research team of Goethe University scanned the brain's participants six times from 8 am to 11 pm. They discovered that the brain excludes background activity in the visual cortex during the day at a time between 8 am and 8 pm

Kell said that this mechanism that changes perception makes driving a car easier during dawn and dusk. But our ancestors developed it to spot potential predators, such as lions, who hunted during these hours of reduced light.

"He would surely have kept us in critical times when night predators appeared. The brain also suppresses activity in the brain's brain region, which could explain why hearing is better in these times, "said Kell.

The participants were certainly better in the visual test at those times when background activity in the brain fell. They were asked to press the button when the poorly visible orange cross detected. They average 32 times 33 times during 8 am and 8 pm

In other times, the participants managed to score 30 times out of 33. Their vision proved to be the weakest at 2 pm, at a time when there is an abundance of natural light.

The human brain improves vision in the days of the day with little natural light

Kell said that the circadian rhythm - a 24-hour cycle that serves as an internal watch of our body - is well documented and researched.

However, previous studies have not yet identified which biological mechanism improves vision at the time of day when there is very little light.

The researchers published their findings in the Nature Communications journal. Their work describes people as a daily active species, which mainly relies on the sense of vision when they are oriented.

In spite of this, people tend to stay active in the morning and evening hours during the twilight, at times when natural light sources are the weakest. This applies to people who have unreliable access to artificial light, such as fire or electric light today.

• 10 May, 2018
• 1334 views