The locus coeruleus (LC), a small subcortical structure in the brainstem, is the brain's
principal source of norepinephrine. It plays a primary role in regulating stress, the sleep-
wake cycle, and attention, and its degradation is associated with aging and
neurodegenerative diseases associated with cognitive deficits (eg, Parkinson's,
Alzheimer's). Yet precisely how norepinephrine drives brain networks to support healthy
cognitive function remains poorly understood–partly because LC's small size makes it …