Retinal circuitry in the European robin

• Applicant: Dr. Anja Günther
• Subject Area: Experimental and Theoretical Network Neuroscience ; Sensory and Behavioural Biology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 508628753

Although birds are highly visual animals, it is surprising how little is known about the connectivity between different cell types within the avian retina. With their tetrachromatic vision and an additional type of rods and double cones, birds developed one of the most complex visual systems among vertebrates. To identify retinal circuits that are evolutionary conserved in all vertebrates or specific to only one vertebrate class, an analysis of species from all major vertebrate classes is needed. Analysing retinal circuits that are responsible for e.g., direction-selectivity, colour vision or high-acuity vision, this project aims to analyse the detailed wiring of all major neuronal cell classes in the European robin retina. The European robin was chosen as model organism because it allows the investigation of as many retina related questions as possible, e.g. in contrast to chicken, the European robin has a central fovea allowing the analysis of high-acuity vision in addition to other retinal circuits such as colour vision or direction-selectivity. The detailed analysis of the morphology and synaptic connectivity between cells in a bird retina requires large high resolution electron microscopic datasets which were very daunting to obtain in the past but can now be provided by an advanced electron microscopic technique called serial section multibeam scanning electron microscopy. The only volume electron microscopic dataset from any bird retina exists from a peripheral part of the chicken retina. To identify common circuits in the bird retina it is important to analyse more than one bird species. Therefore, in preparation to this proposal, I acquired a volume electron microscopic dataset of a peripheral part of the European robin retina. One aim of this proposal is to analyse the synaptic connectivity of retinal cells within this newly obtained dataset and compare it to the already existing chicken dataset. Such a comparison will allow me to investigate general structures or circuits in the bird retina and identify species-specific differences that might be caused by adaptations to different environments. A second aim of this proposal is to acquire a large electron microscopic dataset located in the central area of the European robin retina A large volume is needed to be able to reconstruct retinal cell types with large dendritic or axonal fields such as ganglion cells or amacrine cells. Due to regional changes in the shape and abundance of retinal cell types, a comparison between different retinal regions is needed to get a broader view on fundamental circuits in the retina. Additionally, it will only be possible to analyse the high-acuity circuit in a central part of the retina.

• DFG Programme: WBP Position