Network-level disruptions in vulnerable individuals contribute to enhanced fear generalization in a rodent model of PTSD

Posttraumatic stress disorder (PTSD) manifests in some trauma-exposed individuals through excessive fear generalization to safe contexts and difficulties extinguishing fear. While previous studies have implicated functional changes in fear-regulatory nodes a comprehensive understanding of network-wide alterations remains elusive. We employed a rodent model of PTSD to investigate whole-brain activity patterns associated with fear generalization. Male rats underwent uncontrollable footshocks and 28 days later we measured their generalized fear response in an altered/safe context. Based on freezing responses, we categorized them into resilient and vulnerable subpopulations. We used c-Fos, Neurogranin (for excitatory cells), and Gad67 (for inhibitory cells) immunostaining to assess neuronal activity and cell type involvement across the brain. Signal analysis and detailed semi-automated alignment to the Waxholm Space Atlas revealed altered activity in previously implicated regions like the cingulate cortex and hippocampus. Notably, vulnerable animals exhibited additional disruptions in the retrosplenial cortex, insular cortex, and reticular thalamic region. Further analysis revealed stronger inter-regional correlations and coupling in the resilient subpopulation. These findings suggest that vulnerability to PTSD involves disrupted activity across multiple brain networks and diminished network integration, highlighting the importance of network-level analysis in understanding and potentially treating PTSD.