Arousal increases locus coeruleus blood flow, salience-related brain responses, and modulates negative-valence...

The amygdala helps prioritize emotional over neutral information. However, it responds similarly to positive and negative stimuli, and so is unlikely to be the source of valence-specific effects within affective networks. We hypothesized that the locus coeruleus (LC) is a key contributor to negative biases in attention. Using ultra-high field 7T magnetic resonance imaging, we tested how arousal modulates processing of emotional faces during an oddball task in twenty-two young adults during two separate sessions. Arousal induced by isometric handgrip increased LC cerebral blood flow and amplified brain responses to target and angry faces, but not to happy faces. The amygdala exhibited valence-general responses that were not modulated by arousal. LC connectivity with the default mode network decreased during processing target and angry faces, and arousal further modulated responses in the salience network and visual cortex. Behaviorally, arousal enhanced recognition of angry faces only when allocating attentional resources and memory performance was linked to left LC brain activity. These findings highlight the LC as a key structure through which arousal shapes valence processing, biases attention, and informs mechanisms related to affective disorders.