Network reorganization distinguishes vulnerability and resilience to observational fear

ABSTRACT Individuals vary widely in their responses to stress and threat, with some developing persistent fear after adverse experiences while others remain resilient. Such variability also extends to social contexts, where individuals can acquire information about danger by observing others in distress through observational fear learning. The neural mechanisms underlying individual differences in responses to socially conveyed threat remain poorly understood. Here, we examined how variability in OFL relates to large-scale brain network organization. Rats observed conspecifics receiving tone-shock pairings and were later tested for fear responses to the conditioned stimulus. Behavioral analysis revealed two phenotypes: observational-susceptible rats displaying robust freezing and observational-resilient rats showing freezing levels comparable to controls. Despite these differences, both groups exhibited elevated corticosterone responses, indicating that socially conveyed threat was detected across animals. Brain-wide c-Fos mapping across 84 regions combined with graph-theoretical analysis revealed distinct network architectures associated with each phenotype. These findings suggest that susceptibility and resilience to socially acquired fear emerge from differences in distributed brain network organization.