Introducing the brain: pupil size control (Introduction)

by David Turell , Monday, October 03, 2022, 17:27 (570 days ago) @ David Turell

Depends on the state of the brain's alertness in mice:

https://medicalxpress.com/news/2022-09-pupil-dilation-window-perception.html

"The eyes are often referred to as 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, are now able to provide answers as to why pupil size is influenced by not only sensory stimuli like light, but also by our internal state such as fear, excitement or attention.

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"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 light within seconds, meaning neurons were more green sensitive in a quiet state and became more UV sensitive in an active state.

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

"With the help of eye drops that dilate the pupil, researchers were then able to simulate the higher sensitivity to blue light even for a quiet brain state.

"These results clearly demonstrate that pupil dilation due to an alert 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, recruiting different types of photoreceptors in our retina and thus indirectly changing the 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 adjunct professor of neuroscience at Baylor Dr. Fabian Sinz, said, "We were able to show that the higher neuronal sensitivity to blue light probably helps the mice to better recognize predators against a blue sky.'"

Comment: it is not surprising the brain has feedback loop controlling pupil size. This did not develop by chanced mutations but by clever design.