Deep in the brainstem sits a small but important cluster of neurons known as the locus coeruleus (LC), Latin for “blue place.” It makes up a tiny fraction of the brain’s cells but plays an important role by releasing a crucial chemical messenger known as norepinephrine (NE). NE activates the body’s response to stress or excitement, impacts attention and learning, and affects heart rate.
For a long time, scientists believed the LC (called the blue place because it contains neuromelanin, a dark bluish pigment formed by dopamine and NE) worked like a single loudspeaker, indiscriminately broadcasting a uniform NE signal throughout the brain, triggering it to release this important neurotransmitter. But in a new study published in Nature, Allen Institute scientists used a combination of brain imaging, neural recordings, genetic tools, and behavioral experiments in mice to illustrate that it actually transmits multiple signals through distinct routes with great precision depending on what the mouse experiences.