I happened to come across this blog post: The Brain in Love and Lust
"In a study published in 2002, anthropologist Helen Fisher PhD of Rutgers University and a multi-disciplinary team of experts recruited 40 young people madly in love - half with love returned, the other half with love rejected - and put them into an MRI with a photo of their sweetheart and one of an acquaintance. Each subject looked at the sweetheart photo for 30 seconds, then - after a diversion task - at the acquaintance photo for another 30 seconds.. They switched back and forth for 12 minutes.It makes me think of a Bible verse ... "There is no fear in love, but perfect love casts out fear." (1 Jn. 4:8)
The result was a revealing photo album of the brain in love. Think like a brain scientist and you too would be excited by activity in the right ventral tegmental area. This is the part of the brain where dopamine cells project into other areas of the brain, including the posterior dorsal caudate and its tail, both which are central to the brain’s system for reward and motivation. The sweetheart photos, but not the acquaintance photos, were the cause. In addition, several parts of the prefrontal cortex that are highly wired in the dopamine pathways were mobilized, while the amygdala, associated with fear, was temporarily mothballed."