WHOLE-BRAIN ACTIVITY MAPPING AND CHEMOGENETIC INTERROGATION OF FEAR GENERALIZATION NETWORKS

Post-traumatic stress disorder (PTSD) involves persistent fear responses mediated by dysregulated neural circuits. Current models remain limited to discrete regions (such as the prefrontal cortex, hippocampus, and amygdala), without network-level integration. We employed whole-brain activity mapping in a rat PTSD model to identify fear generalization networks. Adult male rats underwent uncontrollable footshock trauma, followed by four-week incubation and fear generalization testing in a novel context, differentiating vulnerable (high fear) and resilient (low fear) phenotypes. cFos immunolabeling with excitatory and inhibitory markers quantified neuronal activity across the brain, identifying the cingulate and retrosplenial cortices, subiculum, and mediodorsal thalamus as critical nodes. Graph-theoretical analysis revealed divergent network architectures: vulnerable animals exhibited elevated inter-regional co-activation, whereas resilient animals showed concentrated hub centrality. Cellular colocalization analyses attributed these differences to excitatory neurons in the posterior cingulate cortex (PCC). Chemogenetic silencing of PCC principal cells significantly modulated fear memory. To define the mechanism, a whole-brain mapping pipeline was applied to the chemogenetic cohort. Comparative network analyses, identical to the population assessments, validated the behavioral shift toward the vulnerable phenotype in the network functional connectivity. These findings demonstrate that PCC excitability causally governs the global network topology, confirming specific connectivity patterns as drivers of vulnerability. This work advances PTSD neurobiology beyond regional models toward mechanistic circuit-based frameworks.