Circadian rhythm affects everything, even the day we see – Innovita Research

Our bodies function in a cycle called circadian rhythm. It is our internal biological clock, which determines when our body is taking its time to heal, when it is growing and when it is using its other functions. However, up until now we didn’t know that the circadian rhythm affects the way we see. A new research from the University of Helsinki showed that navigating in the dark also depends on the circadian rhythm.

Even if the lighting is the same, mice will use different methods to find visual clues during day and night times. Image credit: Michael Gäbler via Wikimedia (CC BY 3.0)

Your vision depends heavily on the lighting, right? Well, yes, but your eyes can get used to the dark, adapt and see a little bit better even when the lights are dim. However, it all depends if your internal clock thinks its night. Scientists let lab mice to go through a maze. This classic experiment this time was different – the maze was completely dark and there was just a single light at the end that mice had to follow to get out. Simple, right?

The environment was completely controlled. This means that every time the experiment was conducted the lighting was exactly the same, regardless of the time of day. The destination light was very dim, but mice had no problem seeing it. However, they had less problems navigating the maze when they were doing it at night. Why? Because their internal clocks prepared their eyes for the dark time of the day.

This isn’t about optical nerves and the function of the nervous system at all. It is actually about the preparation and the method. Scientists noticed that during the night mice searched for the light more effectively by scanning the environment by, for example, turning around more. If the experiment was repeated several time with the same mice, eventually they started incorporating those night-time moves during daytime. Sanna Koskela, one of the authors of the paper, said: “It's exciting to now show that even in the simplest of tasks – finding a light in the dark – animals can use vastly different behavioural strategies and, what’s more, we are able to quantify day/night differences in them”.

Many animals behave differently from night to day. This is all adaptation. For example, some animals hunt at night, which means they have to pay more attention to small clues that are more difficult to see in the dark. Survival at day and night is different and animals have to use different tools to achieve even the most simplest of tasks.

Scientists already laid out future experiments to research this phenomenon a bit more deeply. They want to see how the brain processes weak signals originating from increasing and decreasing light intensities in the retina at different times of day and night. This can further prove that it is not just about the nerves, but also about the behavioural traits.


Source: University of Helsinki