The locus ceruleus norepinephrine system

Functional organization and potential clinical significance. Benarroch EE. Neurology 2009; 73:1699-1704

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1. NE plays a role in arousal, attention, stress response, long term synaptic plasticity, pain modulation, motor control, energy homeostasis and local blood flow. LC is implicated in sleep and arousal disorders, ADHD, PTSD. Refs 1-9 give review articles. See Annu Rev Neurosci 2005, eg.

2. Changes in LC activity anticipate changes in the behavioral state. LC firing can be tonic or phasic. Tonic activity correlates with wakefulness, decreases in SWS and is abolished in REM sleep. There is a sustained increase in tonic discharge in response to environmental stimuli that elicit behavioral arousal and exploratory behavior. During focused attention and accurate task performance, LC neurons reduce their tonic firing to a moderate rate and respond phasically to task-relevant stimuli. Phasic bursts correspond to highly accurate behavioral responses.