The medial prefrontal cortex (mPFC) plays a crucial role in integrating sensory input for learned stimulus-response associations. However, the link between sensory stimuli and changing behavioral relevance remains poorly understood. We studied how sensory stimuli and neural representations of associated behaviors emerge in mPFC during avoidance learning.We performed mobile population calcium imaging in mice mPFC during an active avoidance task. In this task, mice learned to avoid an aversive foot shock associated with conditioned tone stimuli CS1 and CS2. CS1 was first followed by the shock in case of failed avoidance. After a task switch, CS2 signaled the upcoming shock instead (Fig.A-C).Our single-cell analysis reaffirmed the emergence of behaviorally relevant stimuli representation in mPFC [Le Merre et al. 2021, Jercog et al. 2021] (Fig.D). Interestingly, we found that the cell population responsive to CS1 and CS2 (orange) became more dominant after the task switch in successfully trained mice compared to unsuccessfully trained mice. This cell population mainly contains cells responsive to only CS1 in task 1 and responsive to both tones in task 2 (Fig.E orange-green dots).We performed a decoding analysis to understand the contribution of this adaptive cell population. Our analysis, based on a population activity alignment method [Ehret et al. 2023, Galgali et al. 2023], demonstrated that this adaptive population significantly contributes to tone decoding compared to other populations in tasks 1 and 2 (Fig.F).Our study highlights the importance of an adaptive cell population in mPFC for linking sensory stimuli to changing behavioral relevance.