Scientists map brain's 'blue place': 35,000 neurons, 70cm axon

Researchers at the Allen Institute produced a complete structural and functional map of the locus coeruleus, the brainstem region that releases norepinephrine. The data overturns the loudspeaker model: dorsal neurons project to the cortex and drive learning, while ventral neurons govern engagement. One axon measured 70.32 cm, the longest neuron ever recorded in a mouse.

• Mapping drew on imaging of nearly 35,000 neurons and profiling of about 400,000 cells
• Dorsal LC neurons target the cortex and drive learning; ventral ones go to brainstem and spinal cord
• LC axons average about 35 cm; the longest measured 70.32 cm
• Norepinephrine is the target of depression and ADHD drugs; LC neurons degenerate early in Alzheimer's