Parietal-Frontal Pathway Controls Relapse of Fear Memory in a Novel Context

Fear responses significantly affect daily life and shape our approach to uncertainty. However, the potential resurgence of fear in unfamiliar situations poses a significant challenge to exposure-based therapies for maladaptive fear responses. Nonetheless, how novel contextual stimuli are associated with the relapse of extinguished fear remains unknown. Using a context-dependent fear renewal model, the functional circuits and underlying mechanisms of the posterior parietal cortex (PPC) and anterior cingulate cortex (ACC) were investigated using optogenetic, histological, in vivo, and ex vivo electrophysiological and pharmacological techniques. We demonstrated that the PPC to ACC pathway govern fear relapse in a novel context. We observed enhanced populational calcium activity in the ACC neurons that received projections from the PPC (PPC→ACC) and increased synaptic activity in the BLA-projecting PPC→ACC neurons upon renewal in a novel context, where excitatory postsynaptic currents amplitudes increased but inhibitory postsynaptic current amplitudes decreased. In addition, we found that parvalbumin (PV)-expressing interneurons (PPC→ACCPV) control novel context-dependent fear renewal, which was blocked by the chronic administration of fluoxetine. Our findings highlight the PPC→ACC pathway in mediating the relapse of extinguished fear in novel contexts, contributing significant insights into the intricate neural mechanisms that govern fear renewal.