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Title: Behavioral and optogenetic analyses of reinforcement processing in larval Drosophila
Author(s): Weiglein, Aliće
Granting Institution: Otto-von-Guericke-Universität Magdeburg, Fakultät für Naturwissenschaften
Issue Date: 2020
Extent: 130 Seiten
Type: HochschulschriftLook up in the Integrated Authority File of the German National Library
Type: Doctoral thesis
Exam Date: 2020
Language: English
URN: urn:nbn:de:gbv:ma9:1-1981185920-354697
Subjects: Tierphysiologie
Abstract: Understanding the complexity of reward processing in the brain is one of the major challenges in the contemporary neurosciences. Reward systems play a crucial role in increasing fitness and the avoidance of adverse influcences. Disturbances in these systems may cause neuropsychatric consequences, such as post-traumatic stress disorder or addiction. The present study uses the Drosophila melanogaster larva as model organism. This is due to a fortunate combination of neural simplicity and a surprisingly complex reportoir of behaviors, as well as a rich genetic toolbox together with recent knowledge about their connectomics. In this work, classical behavioral paradigms as well as optogenetics are used to gain deeper insights in the reward learning of this animal. For once, I describe a minimal capacity of the brain, one-trial learning, that is associative learning without repetition. Further on, my work is centered around the detailed parametric specification of an identified ‘reward neuron’, DAN-i1, as well as around the first-time discovery and characterization of relief learning in the larva, which is mediated by a ‘punishiment neuron’, DAN-f1. The center for learning and memory in Drosophila is a higher-order brain structure, called the mushroom body. In order to enable associative learning, it integrates conditioned and unconditioned stimuli. Dopaminergic neurons with distinct ‘polarity’ signal appetitive or aversive reinforcement, receptively, to mushroom body intrinsic neurons. Coincidence detection of the activity of dopaminergic neurons and an odor cue leads to a skew in activity of mushroom body output neurons, causing a given behavior such as approach or avoidance. Interestingly, dopaminergic neurons were found to bring about memories of opposite valence, depending on the event-timing of conditioned and unconditioned stimulus. This principle, known as timing-dependent valence reversal, was reported across species. In the present study, I investigate one dopaminergic neuron of the opposite polarity each, which can establish two opposing types of memory, namely reward versus frustration and punishment versus relief memory, respectively. I further provide evidence that distinct underlying molecular pathways may contribute to the formation of the respective memory types. Thus, the present study paves the way for more detailed analyses of co-transmitters, dopamine receptors, and downstream molecular cascades. In case these results depict a common principle, this does not only have implications for our fundamental understanding, but also for the systemic treatment of the human dopamine system.
Open Access: Open access publication
License: (CC BY-SA 4.0) Creative Commons Attribution ShareAlike 4.0
Appears in Collections:Fakultät für Naturwissenschaften

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