Only about half a million of the brain’s 86 billion neurons make dopamine, and nearly all of them sit in two neighboring patches of the midbrain. From there, two great fiber systems fan out. One drives wanting and motivation. The other keeps movement running.
Tap any part of the brain to see what it does.
Simplified view of the brain sliced down the middle, not to scale. The striatum, nucleus accumbens, amygdala and hippocampus sit off to the side of this slice and are drawn as if seen through it. The split between the two systems isn’t perfectly clean: the substantia nigra and VTA sit side by side and blend into each other, some VTA cells reach the striatum, and some nigra cells reach the cortex. Dopamine also has two small local pathways in the hypothalamus (one controls the hormone prolactin); see Neurotransmitter Pathways.