University of Tübingen: Our emotions determine what we see

International research team decodes connection between mood and visual perception
The pupil size of the eyes is not only affected by light, but also by a person’s inner, emotional state. An international research team consisting of neuroscientists from the Universities of Göttingen and Tübingen and the Baylor College of Medicine in Houston has now been able to provide initial answers to the question of why the pupil size changes with the inner state and whether these rapid, mood-dependent changes in the pupil Changing the way we perceive our surroundings. The results were published in the renowned journal ” Nature “.

State of mind changes pupil size
The eyes are also popularly called the “windows to the soul”. In fact, there is a grain of neurobiological truth behind it. Pupil size is not only influenced by sensory stimuli such as sunlight, but also by our current state of mind such as fear, excitement or concentration. Interestingly, these mood-dependent changes in
pupil size are observed not only in humans but in many other vertebrate species.

Artificial intelligence for data analysis
In experiments, the researchers investigated how mood-dependent changes in pupil size affect the vision of mice. Not only the eyes are decisive for the interpretation of visual impressions, but especially the visual cortex, an important part of the brain that is responsible for visual perception. While the researchers showed the mice different colored images in experiments, they recorded the activity of thousands of individual neurons within the visual cortex. Using state-of-the-art artificial neural networks, the researchers were able to use this data to create a computer model that simulated the actually measured neurons in the brain. They then used this computer model to

Effects on visual perception
These investigations revealed something amazing: When the mice enlarged their pupils due to an alert state of mind, the color sensitivity of the neurons changed from green to blue light within seconds. This was particularly true for neurons that process upper hemisphere stimuli used by mice to observe the sky.

With the help of eye drops that dilate the pupil, the researchers were able to simulate the higher sensitivity to blue light even in a calm brain state. “These results clearly show that dilation of the pupils due to a wakeful brain state can directly affect visual sensitivity and probably visual perception as well. The mechanism here is that a larger pupil lets more light into the eye and this has a direct effect on the recruitment of the photoreceptors in our retina and thus indirectly on the color sensitivity in the visual cortex,” explains Dr. Katrin Franke, research group leader at the Research Institute for Ophthalmology at the University of Tübingen and first author of the study.

But what are the benefits of changing visual sensitivity? Konstantin Willeke, member of the research group led by Prof. Dr. Fabian Sinz, who is also the first author of the study, sheds some light on the matter: “We were able to show that the higher neuronal sensitivity to blue light probably helps the mice to better recognize predators when the sky is blue.” created, still prove to be useful in many ways: “We assume that our model can be used for further experiments to understand visual processing.”

“In addition, such models can be used in the long term to reduce the number of animal experiments,” Willeke continues. “The use of artificial intelligence to evaluate large experimental data sets opens a new era in research. This makes it possible to build ‘digital twins’ of real biological systems. This allows us to run an unlimited number of simulations to generate hypotheses that can then be verified in the biological system.”

The finding that mood-related changes in pupil size affect visual sensitivity has implications for our understanding of vision well beyond predator detection in mice. Further research questions now arise as to how perception in numerous other animals is influenced by this effect. The pupils in our eyes could thus not only be a window into the soul, but also change the way we perceive the world from moment to moment depending on our inner state of mind.