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Neurobiology: How mice see their habitat

Researchers from Munich and Tübingen have developed an open-source camera system that maps the natural environment as rodents see it.

During evolution, animals have adapted to their respective environments to increase their species' chances of survival and reproduction. This also affected how they perceived their environment in the first place. Such evolutionary adaptations include, for example, the positioning of the eyes or the shape of retinal areas with high visual acuity.

But so far, knowledge about this is far from complete. "In the last ten to 15 years, the mouse has established itself as a model for visual information processing," says Professor Laura Busse from the Department of Biology II at LMU. "This was surprising in that it was previously thought that these rodents tended to use mainly their tactile hairs or sense of smell for orientation." Which colours creatures recognise influences their ability to find food, choose a mate or protect themselves from predators.

"We noticed that we don't actually know exactly how the mouse perceives its natural visual environment," Busse tells us. She has been researching this issue as part of the Collaborative Research Centre (SFB) 1233 "Robustness of Vision", together with Professor Thomas Euler from the University of Tübingen, where the SFB is coordinated. "Robustness of vision" alludes to the fact that humans and animals can draw conclusions from limited visual information even in a variable environment. "Together we are investigating visual input in mice and the processing of neuronal signals," says Busse.

Recording the mouse view of the world with a special camera

Mice are dichromats. This means that they have special cones in their retina. These sensory cells perceive electromagnetic radiation in the green (510 nanometres (nm)) as well as in the ultraviolet range (350 nm). "We wanted to know what colour information is available to the mouse in its natural environment and whether the colour statistics in natural scenes are sufficient to explain the function of circuits in the retina," says Busse.

Together, Thomas Euler and Laura Busse's teams have developed a low-cost open-source camera system. Unlike standard cameras, their technology covers the relevant spectral range of rodents in the green and ultraviolet well. A gimbal, i.e. a special suspension for camera systems, makes movements smoother when used in the field and helps to avoid jerkiness.

The scientists used this camera to make recordings in fields when mice were present, at different times of the day. "Until now we knew that in mice the part of the retina with which they perceive the sky is particularly UV-sensitive," says Busse. "The other part, which is more directed towards the ground, has a stronger green sensitivity." The LMU neuroscientist found that precisely such colour differences are common in rodents' natural habitats. The adaptation to this could be a result of evolution - and help the mouse to recognise predators in the sky, for example. Investigations in artificial neuronal networks confirm the assumption.

Scientific contact person:

Prof. Dr. Laura Busse
Phone: +49 (0)89 / 2180-74305 / 74357
Email: busse[at]biologie.uni-muenchen.de
https://www.neuro.bio.lmu.de/members/system_neuro_busse/busse_l/index.html

Original publication:

Qiu Y et al: Natural environment statistics in the upper and lower visual field are reflected in mouse retinal specializations. Current Biology 2021
https://www.sciencedirect.com/science/article/abs/pii/S096098222100676X
https://doi.org/10.1016/j.cub.2021.05.017