Noradrenergic efferent subsystems that gate traumatic social learning

Individuals experience varying magnitudes of stress in their daily lives. Although stress responses facilitate adaptive processes to cope with changing environments, severe stress can lead to traumatic learning and anxiety disorders. However, the neuronal mechanisms underlying the influence of stress severity on these processes remain unclear. Here, we show that traumatic social stress engages anatomically distinct locus coeruleus noradrenergic (LC ^NA ) subpopulations that exhibit dynamic responses scaled to aversive salience. Using whole-brain activity and axonal projection mappings, we identified projectome subtypes of LC ^NA neurons, which are differentially recruited by single versus consecutive aversive social experiences. While hippocampus-projecting LC ^NA neurons responded to general social contacts, thalamus-projecting LC ^NA neurons tracked the aversive salience of social stimuli. Functional manipulations revealed a bidirectional role of thalamus-projecting LC ^NA neurons in social avoidance learning. These findings reveal the functional architecture of LC ^NA subsystems that regulate traumatic social learning via dynamic scaling to aversive salience.