The locus coeruleus (LC), whose Latin name translates to "blue spot", is a small nucleus located in the brainstem's pons. It owes its name to its blue color, a result of melanin granules inside its neurons. The LC is a key component of the reticular activating system and the primary site in the brain for the synthesis of norepinephrine (noradrenaline). This system, known as the locus coeruleus-noradrenergic system (LC-NA), is involved in many processes, including mediating the sympathetic effects during stress. The LC-NA system plays a critical role in maintaining vigilance and responsiveness to unexpected stimuli.
The LC affects wakefulness and attentiveness, responses to stress, coping with anxiety and fear, and the creation of memories and learning. It sends signals, via norepinephrine, throughout the brain and receives inputs from the central nervous system. Recent research indicates that the quality of REM sleep is linked to the activity of the locus coeruleus. Specifically, a reactive LC during wakefulness correlates with reduced REM sleep quality, especially in individuals aged 50-70. Furthermore, the LC's degeneration is associated with the initial deterioration and worsening of Alzheimer's disease. The LC is among the first regions of the brain to exhibit Alzheimer's-like changes, sometimes as early as 20 to 30 years of age.
