Dilated pupils: a window on perception – Attractive Area

The eyes are often called the “windows to the soul”. In fact, there is a grain of neurobiological truth to this. An international research team from the universities of Göttingen and Tübingen, Germany, and Baylor College of Medicine in Houston, is now able to provide answers on why pupil size is influenced not only by sensory stimuli. like light, but also by our internal state such as fear, excitement or attention.

The conclusions, published in the current edition of Naturehelp explain whether these rapid, state-dependent changes in pupil size, found not only in humans but also in other vertebrates, affect the way we perceive our environment.

Artificial intelligence for data analysis

The researchers began their work by studying how state-dependent changes in pupil size affected vision in mice.

“While the eyes convert light into neural activity, it is the brain that is crucial for the interpretation of visual scenes,” said Dr. Katrin Franke, research group leader at the Ophthalmology Research Institute of the University of Tübingen and first author of the study.

In their experiments, the researchers showed mice different colored images and recorded the activity of thousands of individual neurons in the visual cortex, a brain area particularly relevant to visual perception. Based on these recordings, they used deep neural networks to create a computer model as a digital twin of the cortex, simulating the responses of a large number of neurons in the brain. They then used this computer model to identify the optimal visual light stimulus for each neuron, i.e. each neuron’s “preferred image”.

Effects on visual perception

This model revealed something quite interesting: when the mice dilated their pupils due to an alert state of mind, the color sensitivity of the neurons changed from green to blue within seconds, which means that the neurons were more sensitive to green in a calm state and became more UV. sensitive to the active state.

This was especially true for neurons that sample upper hemisphere stimuli used to observe the sky. In subsequent experiments, they were able to verify that this also occurs in real biological neurons.

Using eye drops that dilate the pupil, the researchers were then able to simulate the greatest sensitivity to blue light even for a calm brain state.

“These results clearly demonstrate that pupil dilation due to an alert state of the brain can directly affect visual sensitivity and probably also visual perception. The mechanism here is that a larger pupil lets more light into the eye, recruiting different types of photoreceptors in our retina and thus indirectly altering color sensitivity in the visual cortex,” Franke said.

But what are the benefits of this change in visual sensitivity? Konstantin Willeke, co-first author of the study and member of the research group led by Baylor Assistant Professor of Neuroscience, Dr. Fabian Sinz, said: “We were able to show that the higher neural sensitivity to blue light probably helps mice recognize predators better against blue skies. »

The computer model created by the researchers may also prove useful in many ways. The researchers hope that others could use this model for further experiments to understand visual processing.

“Combining high-throughput experimental data with AI modeling opens a new era in neuroscience research. They allow us to extract data from precise digital twins of real-world biological systems,” said Sinz, who is currently a professor at the University of Göttingen and one of the principal investigators of the study. “With these digital twins, we can perform a virtually unlimited number of experiments in a computer. In particular, we can use them to generate very specific hypotheses about the biological system that we can then test in physiological experiments. »

Dr Andreas Tolias, also the study’s principal investigator and Professor and Director of the Center for Neuroscience and Artificial Intelligence at Baylor, said: “The finding that changes in pupil size related to the state of the brain affect visual sensitivity has implications for our understanding of vision. far beyond the detection of predators in mice. Further research questions now arise as to how the perception of many other animals is influenced by this effect. The pupils of our eyes could therefore not only be a window to the soul, but also change the way we perceive the world from moment to moment depending on our inner state of mind. »

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Dilated pupils: a window on perception – Attractive Area

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