The medial prefrontal cortex (mPFC) supports highly dynamic behavior on time scales of seconds as well as long-term memory in form of stable neuronal representations over the course of weeks. How these two fundamentally different time scales of cognitive operation are reconciled in the prefrontal circuitry is not well understood. In this project, our main objective is to examine the dynamics and the stability of prefrontal neuronal ensembles during the execution of short- (i.e., working memory) and long-term (repeated exposure to a memory task) memory using 1-Photon and 2-Photon population imaging and single-unit recordings in behaving mice. We will address the open question how dynamically changing and stable representations might be simultaneously realized in the prefrontal network to support cognitive operations. Specifically, we will ask how prefrontal cell assemblies encode different environments (context flexibility), and how they represent newly learned information over prolonged time-periods (representational dynamics). In addition, we will use axonal imaging to address how prefrontal assemblies are shaped by the activity of input streams to determine the influence of afferents on the dynamics of short- and long-term contextual memory represented in the mPFC. This project will thus reveal how prefrontal neurons support stable and dynamic coding over a larger span of behaviourally relevant time scales. Moreover, with this approach we will contribute an experimental framework to conceptually address the spatial and temporal stability and dynamics of prefrontal assemblies during goal-oriented learning.