Timing-dependent valence reversal: DANs, shock, and beyond

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Obtaining rewards and avoiding punishment are powerful goals of behavior. Fittingly, evolutionarily conserved processes have evolved to learn predictors of their occurrence. These are studied in detail in many species, including humans. In insects, the role of the mushroom body is well documented in this respect. In contrast, the present project focuses on the much less acknowledged but equally important process of learning from reward and punishment termination. Indeed, it feels good to receive a reward (Gain) but it feels bad when the reward terminates (Loss). These experiences result in appetitive and aversive memory, respectively, of associated cues. In turn, receiving punishment (Pain) versus its termination (Relief) result in aversive and appetitive memory. Such timing-dependent valence reversal thus defines a 2x2 matrix of reinforcement-related memories that is common to animals and humans alike (Gerber et al Curr Op Behav Sci 2019).The present project specifically focuses timing-dependent valence reversal in Drosophila melanogaster, a simple experimental system with enticing analytical power to reveal general principles in behavioral neurogenetics. We i) study the organization of timing-dependent valence reversal at the level of single dopaminergic neurons innervating the mushroom body; ii) investigate the genetic architecture of timing-dependent valence reversal with an emphasis of the molecular cascades downstream of dopamine receptors expressed in the mushroom body; iii) and explore the role of timing-dependent valence reversal in higher-order forms of learning.