FIGURE 1.

Delirium and the locus coeruleus (LC) noradrenaline system. This is a schematic hypothesis of how high or low arousal might induce more phasic vs. tonic LC activation. The altered LC activation might cause the hyper- or hypoactive forms of delirium via modulating the release of noradrenaline in different brain regions (bottom-up modulation); consequently, altered noradrenergic activity in brain regions might affect LC activity (top-down modulation).