Cell Type-Specific Microcircuit Dynamics During Fear Conditioning in the Prefrontal Cortex

Fear, essential for survival, is regulated by complex neural circuits, with the medial prefrontal cortex (mPFC) serving as a key controller. Within the mPFC, the balance between excitatory pyramidal neurons and inhibitory interneurons—specifically parvalbumin (PV), somatostatin (SST), and vasoactive intestinal peptide (VIP) types—orchestrates fear responses. However, the precise dynamics by which these neuronal ensembles orchestrate the progression of conditioned fear remain poorly understood. In this study, we developed a time-series analysis to examine the dynamic interactions among these four cell types during fear conditioning, followed by optogenetic validation. Our results indicate that during fear learning, PV and SST interneurons modulate the activity of CaMKIIα-expressing pyramidal neurons. In contrast, during recall phase, SST and VIP interneurons, PV interneurons acting through CaMKIIα-positive pyramidal cells appear pivotal. Conversely, during extinction, VIP and SST interneurons exert stronger influence via CaMKIIα-expressing pyramidal neurons. These findings provide new insights into dynamic, cell-type-specific interactions within the mPFC that underlie fear behavior progression and offer a framework for probing the function of these microcircuits in complex behaviors. Our work offers a promising tool for probing the function of these microcircuits in complex behaviors.