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Untersuchung von Form und Funktion eines Insektenneurons anhand von Kompartimentmodellen
Citation key Schoenknecht2011
Author Susanne Schönknecht
Year 2011
School Technische Universität Berlin
Abstract The aim is to investigate the relationship between form and function of the MN5 which is a motoneuron of the tabaco hornworm manduca sexta. Therefore, reconstructions of neuronal morphology are made in various stages of development. For this, the dendritic branching structure as well as the diameters and lengths of dendritic segments are extracted from available confocal data sets. The resulting dendritic trees based on cylindric segments are transferred as multi compartment models in neuron simulation environment NEURON and GENESIS. To include electrophysiological properties of the neuron in the model, the electrical parameters of the passively behaving cell membrane are explored. For an optimal balance between simulation effort and accuracy different methods for the reduction of compartments are presented and compared. On the basis of the compartment models, selected morphological characteristics of the stages Larva, W4, P5 and Adult are studied. Emerging differences are highlighted, and mutual dependencies are discussed with respect to their importance for function. Specific simulations of the propagation of action potentials and the transfer of postsynaptic spikes are carried out on the model of the stage P5, and are discussed particularly with respect to their relevance for growth processes. To describe the functional behavior, resulting from the spread of action potentials or from the transmission of postsynaptic potentials, electrical transmission properties are put in relation with respect to form, and compared on the four stages of development. This is done by simulations of the patch-clamp method or by simulations of current pulses, and the spatial and temporal decay of the membrane potential is projected on the dendritic tree. A comparison between the temporal and spatial decay of the voltage curve allows the interpretation that the larval dendritic tree can be assigned to act as an integrator, while the dendritic tree of the adult neuron behaves as a coincidence detector. This behavior would support the functional requirements that are placed on the neuron in the respective stage of development.
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