Molecular and neuronal mechanisms underlying learning and memory in Drosophila larvae

Abstract

What is learning? How is memory being formed? It seems that learning and memory are different concepts, which nevertheless share a common ground. Like two sides of the same coin. You can not have memory without learning, but you can forget what you have learned. Therefore, establishing a memory is a highly complex and dynamic process. Different molecular changes, structural changes as well as physiological changes within neurons are involved in the process of forming a specific memory (also known as memory trace). It is generally assumed that changes in synaptic transmission is a fundamental cornerstone in the formation of memory and it is conserved throughout the animal kingdom. These changes are either reversible and refer to labile, short-lasting memories, or they are persistent and refer to longer-lasting memories. Persistent memories, by definition, are resistant to anesthetic disruption and require consolidation processes, which in turn require transient changes of intracellular signalling cascades that ultimately lead to de-novo protein synthesis. Thereby changes in intracellular signalling cascades alter synaptic efficiency and provide the feature of transforming learned behaviours into persistent memories. It was shown in Drosophila adults that memory formation after aversive Pavlovian conditioning consolidates from a labile short-term component to a more stable and longer lasting form within in hours. This process requires the timely controlled action of different cellular components. Beside this gradual transition exists another memory component in parallel: an anesthesia resistant memory (ARM), which is resistant to cold shock treatment and independent from the requirement of de-novo protein synthesis. However, the underlying biochemical mechanisms of forming ARM are less characterized. To date, the radish (rsh) gene is the only molecular link to the poorly understood ARM formation. Compared to adult Drosophila, memory formation was only sporadic analyzed at its larval stage and comprehensive analysis of the involved neuronal and molecular mechanisms are still absent. The aim of my work is therefore to analyse the underlying molecular and neuronal mechanisms involved in the formation of learning and memory in Drosophila larvae.