Neural encoding of color and magnetic fields in the pigeon.

• Applicant: Dr. Simon Nimpf
• Subject Area: Cognitive, Systems and Behavioural Neurobiology ; Sensory and Behavioural Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 570793845

Birds rely extensively on vision for retrieving information about their surroundings. Tracking of prey, foraging, communication with con- and heterospecifics and navigational behaviour, all depend on optical systems with high spatiotemporal acuity and precise color discrimination. The natural ecology of birds demands a visual sense that is far superior to that of humans and other mammals and reveals a world of colors that we do not have access to. As humans, our experience of color vision is limited to a trichromatic space ranging from violet to red, defined by the spectral sensitivity of our 3 cone photoreceptor types in the retina (~400–700 nm). Some animals, such as birds, have 5 cone-types permitting them to detect light in the UV spectrum, which is invisible to the human eye (~350-700 nm). Consequently, the ultraviolet reflections of a male pigeon’s breast plumage appear different to us compared to a female pigeon it is attempting to court. Interestingly, research has shown that another sensory modality, elusive to the human observer, called magnetoreception, might be intimately linked to the visual system and the detection and processing of light of different wavelengths. European robins, for example, display proper migratory behavior towards the seasonally appropriate magnetic field direction in the presence of light in the blue-green spectrum but fail to do so under red light. How do birds process color information and magnetic field information? While substantial progress has been made in understanding the neural encoding of color in mammals, the central processing of color in tetrachromatic animals, such as birds, remains mostly unexplored. Moreover, how magnetic fields are processed and encoded in the bird brain and if the processing is linked to the presence of certain wavelengths of light is not well understood. Our main objective is to elucidate the operating principles of color coding on the single neuron and the population level in the terminal station of the thalamofugal visual pathway of pigeons, and explore if, and how, this might be influenced by magnetic stimuli. Using newly developed state-of-the-art in vivo two-photon calcium imaging methodology and high-density, multi-channel Neuropixels silicon probes, we aim to expand our knowledge of the neuronal computations underlying color and magnetic field processing in pigeons.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr. Laura Busse