How do GABAergic inhibitory interneuron types in the prefrontal cortex contribute to the formation and stabilization of context and rule encoding in active cell assemblies? We address this topic by applying 2-photon calcium imaging and by manipulating neuronal activity of interneuron types with optogenetic holographic manipulation. The targeting of the holographic manipulation will be based on machine learning approaches allowing predictions about the roles of individual neurons. Interactions on a structural level will be investigated in ex vivo approaches. Furthermore, we will examine how the contribution of interneurons to the population code changes over time, and in dependence on the learning process.