P027 A functional network model for body column neural connectivity in Hydra
Wilhelm Braun*1,2, Sebastian Jenderny4, Christoph Giez5,6, Dijana Pavleska5, Alexander Klimovich5,
Thomas C.G. Bosch5, Karlheinz Ochs4, Philipp Hövel7, Claus C. Hilgetag1,3
1Institute of Computational Neuroscience, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
2 Faculty of Engineering, Department of Electrical and Information Engineering, Kiel University, Kaiserstraße 2, 24143, Kiel, Germany
3Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA, 02215, USA
4Chair of Digital Communication Systems, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, North Rhine-Westphalia, Germany
5Zoological Institute, University of Kiel, Christian-Albrechts-Platz 4, 24118 Kiel, Germany
6The Francis Crick Institute, London NW1 1BF, UK
7Theoretical Physics and Center for Biophysics, Saarland University, Campus E2 6, Saarbrücken, 66123, Germany
*Email: wilhelm_braun@icloud.com
Introduction
Hydrais a non-senescent animal with a relatively small number of cell types and overall low structural complexity, but a surprisingly rich behavioral repertoire. The main drivers ofHydra’s behavior are neurons that are arranged in two nerve nets comprising several distinct neuronal populations. Among these populations is the ectodermal nerve net N3 which is located throughout the animal. It has been shown that N3 is necessary and sufficient for the complex behavior of somersaulting [1] and is also involved inHydrafeeding behavior [2, 3]. Despite being a behavioral jack-of-all-trades, there is insufficient knowledge on the coupling structure of neurons in N3, its connectome, and its role in activity propagation and function.
Methods
We construct a model connectome for the part of N3 located on the body column by using pairwise distance- and connection angle-dependent connectivity rules. Using experimental data on the placement of neuronal somata and the spatial dimensions of the body column, we design a generative network model combining non-random placement of neuronal somata and the preferred orientation of primary neurites. Additionally, we study activity propagation in N3 using the simple excitable Susceptible-Excited-Refractory (SER) model and a more complex neuromorphic Morris-Lecar model.
Results
We show [4] that the generative network model yields good agreement with experimental data. We then show that the simple excitable dynamical SER model generates directed, short-lived, fast propagating patterns of activity. In addition, by slightly changing the parameters of the dynamical model, the same structural network can also generate persistent activity. Finally, we use a neuromorphic circuit based on the Morris-Lecar model to show that the same structural connectome can, in addition to through-conductance with biologically plausible time scales, also host a dynamical pattern related to the complex behavioral pattern of somersaulting.
Discussion
Our work provides a systematic construction of the structure of a subnetwork ofHydra’snervous system. By assuming that the ectodermal body column network inHydrais essentially two-dimensional, we designed a generative network model that is in agreement with measured
structural quantities and supports two different activity modes, each presumably controlling
different types of behavior inHydra. We speculate that such different dynamical regimes act as dynamical substrates for the different functional roles of N3, allowingHydrato exhibit behavioral complexity with a relatively simple nervous system that does not possess modules or hubs.
Acknowledgements
WB would like to thank Kayson Fakhar, Fatemeh Hadaeghi and Mariia Popova for helpful discussions. Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434434223 – SFB 1461.
References
[1]10.1016/j.cub.2023.03.047
[2]10.1016/j.cub.2023.10.038
[3]10.1016/j.celrep.2024.114210
[4]10.1101/2024.06.25.600563
