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Sensory processing in the medicinal leech 1 Sonja Meiser , 1 Alexander Trende , Gerrit 2 Hilgen , Jutta 1Computational Neuroscience, University of Oldenburg, 1 Kretzberg 26111 Oldenburg, Germany 2Institute of Neuroscience, Newcastle University, NE1 7RU, United Kingdom [email protected], [email protected], [email protected], [email protected] The medicinal leech as a model organism for establishing the neuronal base of behavior Assumption: Common strategies for producing behaviors can be found in all species with a structured nervous system. βΊUse simple systems like the segmented medicinal leech to study how the properties of the neurons and their interconnections produce a behavior [1]. Identify the connectivity and functionality of the involved neurons by using experimental and theoretical methods Mechanoreceptors T, P and N-Cells Interneurons Electrophysiology (Voltage-sensitive-dye Imaging [5]) Motorneurons Causality Analysis Compare the cell responses with various statistical methods to find directed connectivity. Precise behavior: Local Bend-Reflex [2,3] πΏπβπ Fig. 1: The medicinal leech. The leech is a segmented annelid with 21 ganglia. The ventral side of a ganglion contains 400 neurons. The three different sensory neurons are colored in yellow (T-Cell for touch perception), blue (P-Cell for pressure perception) and green (N-Cell for nociception). Fig. modified from [1,4]. During the local-bending-behavior, the leech bends away from the touch location. Fig. Modified from [3] Fig. 2: VSD-Set-Up to record the activity of around 100 neurons How is sensory information processed? It was shown in [6] that a skin stimulation activates a large number of cells. Among others, the pressure sensitive P-Cell and a cell of unknown function, the AP-Cell, were active. ππ = πππ πππ Possible Network Analysis To fully understand how a certain behavior is 4 produced, we have to find out how many and which R2 cells are active. Statistical Connection? AP 1 and machine learning based R1 P 3 2 methods are applied. A Fig. 4: Multiple active Cells B ο¬ο¬ο¬ p=7.5e-06 To find directed connectivity causality analysis methods like Granger Causality are applied. These Fig. 5: Cell response for two different cells This C Fig. 3: P-AP-Connection. (A) Stimulation of the P-Cell with 1.5 nA current leads to a visible and (B) significant increase in the spike rate of the AP-Cell in comparison to the spontaneous activity. (C) Morphology of the APCell. The main process goes contralaterally / posteriorly before it splits and leaves the ganglion via the roots like a motorneuron. Scale bar : 100 µm Filled with Neurobiotin and detected with Streptavidin Cy3. Image Processing: confocal laser scanning microscope and ImageJ References 1) Kristan Jr. WB, Calabrese RL, Friesen WO. Neuronal control of leech behavior. Prog Neurobiol 76: 279β327, 2005. 2) Kristan WB. Sensory and Motor Neurones Responsible for the Local Bending Response in Leeches. J Exp Biol 96: 161β180, 1982. 3) Thomson EE, Kristan WB. Encoding and Decoding Touch Location in the Leech CNS. J Neurosci 26: 8009β8016, 2006. 4) Higgins A, Yuan S, WangY, Burrell BD. Differential modulation of nociceptive versus non-nociceptive synapses by endocannabinoids. Mol Pain 9: 26, 2013. 5) Miller EW, Lin JY, Frady EP, Steinbach PA, Kristan WB, Tsien RY. Optically monitoring voltage in neurons by photo-induced electron transfer through molecular wires. Proc Natl Acad Sci 109: 2114β2119, 2012. 6) Fathiazar E, Anemüller J, Kretzberg J. Statistical Identification of Stimulus-Activated Network Nodes in Multi-Neuron Voltage-Sensitive Dye Optical Recordings. 38th annual International Conference of the IEEE Engineering in Medicine and Biology Society. Orlando: 2016. leads to can predict new unknown connections. different network states for different stimuli. To verify these predicted connections intracellular recordings are performed for the specific Fig. 6: Distinct network state cell pair. Conclusion A combination of experimental and theoretical methods can be used to identify unknown neuronal connections and network states in the leech ganglion to improve the understanding of the sensory processing.
