There were differences -- long-term romantic love lit up many more brain regions than early-stage love -- but both groups showed significant activity in the dopamine-rich ventral tegmental area.

ROMANCE (right): In newly-in-love couples, romantic feelings light up the ventral tegmental area in the midbrain (not shown) — also activated by cocaine and chocolate.

The ventral tegmental area is a clump of cells that make dopamine, a natural stimulant, and sends it out to many brain regions [when one is in love].