Abstract
<title>Abstract</title> <p>Vigilance is an adaptive state that prioritizes monitoring of potentially significant cues and can be heightened by stress. Whether this stress-induced enhancement arises from global amplification of existing neural ensemble activity or selective reorganization of neural ensembles remains unclear. Here, we characterized a carbonic anhydrase 12-defined claustral subpopulation enriched among stress-responsive claustrum neurons and preferentially projecting to frontal cortical regions involved in cognitive control. Longitudinal calcium imaging revealed context-specific vigilance ensembles. Following social defeat stress, these ensembles were remapped, with enhanced event-related responses, vigilance coding, and predictive power, without widespread expanding the responsive population. Optogenetic activation of this population biased behavior toward vigilance, evident as reduced locomotion in an open field and as target-directed gazing with reduced defensive immobility in social interaction. These findings demonstrate that stress reorganizes claustral vigilance coding, characterized by changes in ensemble allocation together with enhanced representational strength, rather than global amplification of existing neural activity.</p>