Our understanding of the cellular mechanisms of classical conditioning, where a neutral stimulus is associated with a temporally overlapping reinforcing stimulus, has made substantial progress in recent years. However, when the two stimuli are temporally disjunct, a non-associative trace of the first stimulus is necessary to build up a transient "bridge" allowing the nervous system to form an association. Intriguingly, the hedonic value of the stimulus can even change with time, e.g. when the trace of an aversive stimulus changes into "relief". The neuronal substrate for stimulus traces is as yet unknown, as are their physiological mechanisms. In this study, we will exploit the power of Drosophila melanogaster to tackle these issues. We will combine genetic network manipulations, state-of-the-art physiology, and computational modeling to understand the neurobiology of stimulus traces. To do so, we will tightly link our diverse expertise of behavior, physiology, genetics, and mathematical analysis. Because the studied stimulus traces are closely related to complex forms of memory, such as working memory, the mechanisms revealed in this project are also likely to be relevant for cognitive memory tasks in humans.
