The ability of frogs to distinguish colors in the dark clearly surpassed even the fairly good vision of man.

Frog distinguishes colors better when fleeing than when mating, and the mouse perceives dim lights better at night than during the day. Thus, the sensitivity of vision depends on the behavioral task, according to a recent study by the University of Helsinki and Aalto University. dissertation research.

Petri Ala-Laurilan and Kristian Donnerin a research group led by led to find out what things limit the sensitivity of vision in low light and how close to the absolute limits set by physics visual performance can get.

Neuroscientist at the University of Helsinki Sanna Koskela says that vision is limited in low light, especially by two factors.

Light is divided into individual particles, or photons, and the stars in the night sky, for example, become only a few photons for the light-sensing cells of the eye. Light is quantized, that is, sometimes a flash of light becomes three photons and sometimes six. Such random variation sets the first physical limit on vision.

According to Koskela, however, this limit is almost impossible to achieve, as biological noise brings an additional challenge to night vision. It inevitably arises in all mechanisms of the nervous system, as there is some random variation associated with each molecule and biological process.

In studies it turned out that the vision of experimental frogs and mice in the dark reached surprisingly close to the absolute limits set by physics.

For example, the ability of frogs to distinguish colors in the dark clearly exceeded the quite good performance of the human visual sense under the right conditions.

However, performance depends on the context and the behavioral task, ie whether there has been an evolutionary need to push biological performance to the extremes, says Koskela.

The first study tested the color vision of frogs in near pitch black.

The frogs were selected as experimental animals because, unlike other vertebrates, they have two types of rod light sensory cells for night vision. At least two types of photosensitive cells are required for color vision, corresponding to different wavelengths of light, i.e. colors.

Color vision was tested in three different behavioral tasks: predation, pair selection, and escape. In the predation task, the frogs had to choose between two objects of different colors in the dimming lighting, and if chosen correctly, they were rewarded with a worm.

In the escape mission, the frog was enclosed in a light-tight container from which they tried to escape by jumping towards a light source on the roof. In previous experiments, it had been found that frogs prefer to jump towards the blue light because they interpret it as the sky.

The researchers compared the frogs jumps between two different colored light sources and found that in the escape mission, their night vision reached close to the extremes set by physics. This did not happen in other positions.

A frog in the rainforest of Borneo.Picture: SCUBAZOO / SCIENCE PHOTO LIBRARY

Similar observation was also made in mice. In the experiment, the mouse was swam into a pitch-dark labyrinth with dim light at the labyrinth exit. Mice were taught that light directed out of the maze, and slowly the light was dimmed. The experiment was repeated both night and day.

The researchers found a difference in behavior: mice found light better at night than during the day. The difference between the times of day was as much as tenfold.

To the researchers surprise, the difference was not explained by changes in the photosensitivity of the mices eyes but by the animals behavioral strategy. In nocturnal experiments, mice seek light more efficiently by turning more. The mice also observed the light source for a longer time before deciding where to go swimming in the maze.

When mice that participated in the night experiment did the same experiment during the day, they took advantage of this better strategy and cleared the maze more efficiently than mice that had not performed the experiment at night.

Never before have animal behavioral strategies been analyzed with such precision.

Koskelan according to one of the key challenges in neuroscience is to understand how neural calculations of neural networks determine animal behavior.

It is often almost impossible to study this, as there are billions of neural networks and calculations relevant to each behavioral state. It is therefore difficult to find out which neural networks are active at any given time and are responsible for a particular behavioral task.

For example, the retinal neural network makes an enormous number of calculations of light distribution to provide an idea of colors, shapes, and movements before this information is sent along the optic nerve to the brain.

Twilight vision simplifies these problems, because in pitch black, neural calculations mainly answer the simple question of whether you saw or did not see, says Koskela.

In the future, he would like to find out more about what causes different behavioral strategies in the brain according to task and time of day.

My own hypothesis is that these are areas of the brain that affect alertness and decision-making.

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Neuroscience The frog sees better when fleeing than when mating The animal's vision depends on what vision is needed at any given time - Pledge Times