FUNCTIONAL NEURONAL ENSEMBLES ENCODE AND STORE SAFETY MEMORY IN THE DMPFC

The ability to learn and remember safety signals is essential for survival and adaptation. However, compared to threat signals, the neural mechanisms underlying safety signal processing remain largely unknown. Here, we identify the dorsomedial prefrontal cortex (dmPFC) as a key brain region for encoding safety memory. When both safety signals (unpaired with foot shocks) and threat signals (paired with foot shocks) are present, we used the FosTrap system to label and manipulate responsive neurons in mice and found that the dmPFC selectively forms a specialized neuronal ensemble for safety signals but not for threat signals. This safety-related ensemble, composed of both excitatory and inhibitory neurons, undergoes plasticity and suppresses fear expression through projections to the amygdala. Using in vivo calcium imaging, we found that dmPFC neurons exhibit distinct response and coding patterns to safety versus threat signals, characterized by differential population recruitment and desynchronized network dynamics, highlighting cortical features critical for safety memory processing. Moreover, by specifically labeling the safety-related ensemble and selectively monitoring and manipulating its activity during calcium imaging, we characterized its functional role in shaping network-level features underlying the encoding and retrieval of safety memories. These findings demonstrate that the dmPFC encodes safety memory through specialized neuronal ensembles with unique network dynamics, offering mechanistic insight into how cortical circuits differentiate and process safety versus threat signals.