An international team comprised of researchers from Freie Universität Berlin and the University of California, Santa Barbara have carried out the first-ever systematic analysis of all synaptic connections in the brain of an adult animal. This pioneering research focused on the connectome – a comprehensive map of neural connections in the brain – of the fruit fly Drosophila melanogaster. The results provide groundbreaking insights into the neuronal networks that enable visual navigation and were published in a special edition of Nature. The article, “Connectomic Reconstruction Predicts Visual Features Used for Navigation,” is available online at https://www.nature.com/articles/s41586-024-07967-z.

The research team, led by Professor Mathias Wernet (Freie Universität Berlin) and Professor Sung Soo Kim (University of California, Santa Barbara) was able to show that fruit flies have at least ten distinct parallel synaptic channels for processing visual information on its way to the central brain. “This is a remarkable discovery, showing that complex visual processing mechanisms are at work even in the brains of small organisms,” says Wernet, who leads a research group working on neural circuits at Freie Universität.

Three researchers are credited as first co-authors of the study: research associate Dustin Garner, PhD student Jennifer Yuet Ha Lai, (both University of California, Santa Barbara), and doctoral student Emil Kind (Freie Universität Berlin). Using electron microscopic data, the researchers were able to reconstruct more than 5,000 neurons in the brain of the fruit fly Drosophila melanogaster, including the chemical synapses between them. In doing so, the scientists created the first complete representation of all visual pathways to the central complex of a fruit fly’s brain. The central complex is an ancestral structure found in insects’ brains that plays an important role in making decisions related to navigation.

“The results of this groundbreaking work are allowing us to draw conclusions on the nature of the visual stimuli these flies are processing, as well as the functional qualities of the neurons involved,” explains Wernet. The team of international researchers was then able to confirm certain predictions in experiments using a 2-photon microscope that allows visualization in vivo.

Professors Wernet and Kim are also authors on a second article that was published in the same edition of Nature under the title “Neuronal Parts List and Wiring Diagram for a Visual System” (https://www.nature.com/articles/s41586-024-07981-1). This research was carried out in collaboration with professors Sebastian Seung and Mala Murthy (Princeton University), among others, and provides a more in-depth analysis of the neuronal components and circuitry that make up the visual system of the fruit fly.

The results of both studies represent an important basis for future research. “In the future, these connectomic data will serve as an important foundation for planning and interpreting physiological work or behavioral experiments aimed at better understanding navigation processes,” says Wernet.

Further Information

Publications

• Garner, D., E. Kind, J. Y. H. Lai, et al. “Connectomic Reconstruction Predicts Visual Features Used for Navigation.” Nature 634 (2024): 181–190. https://doi.org/10.1038/s41586-024-07967-z

• Matsliah, A., S. Yu, K. Kruk, et al. “Neuronal Parts List and Wiring Diagram for a Visual System.” Nature 634 (2024): 166–180. https://doi.org/10.1038/s41586-024-07981-1

 Contact

Prof. Dr. Mathias Wernet, Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Email: mathias.wernet@fu-berlin.de, Webpage: Wernet Group “Neural Circuits:” https://www.bcp.fu-berlin.de/en/biologie/arbeitsgruppen/neurobiologie/ag_wernet/index.html