Phasic locus coeruleus activity regulates cortical encoding of salience information

Locus coeruleus (LC) function has been associated with focused attention across species. LC neurons fire tonically or with short phasic bursts. We found that phasic, but not tonic, LC activity produced attentional signals across cortex, including the P300 event-related potential, and revealed distinct long-latency signals in sensory networks. These long-latency signals were seen in subpopulations normally activated by intense or salient stimuli, meaning that phasic LC activation produced salience in sensory neurons. Phasic LC-generated sensory salience signals were tightly temporally regulated, and precisely timed phasic LC activation was able to generate "false salience" in sensory processing networks, in the absence of intense stimuli. Importantly, LC-induced salience signals occurred without changes in arousal, demonstrating independent mechanisms of LC-mediated arousal and attention.