Heart-ache can be a literal thing, as well as a metaphor for all those weepy, jilted-lover torch songs.
Consensus thinking in the peer-review literature is that the parts of one's brain responsible for physical pain, the dorsal anterior cingulate and anterior insula, also underlie emotional pain.
Researchers at Columbia University in New York recruited 40 people who'd recently ended a romantic relationship, put them in a functional magnetic resonance imaging machine, and recorded their reactions to physical and then emotional pain.
Physical pain was created by heating the person's left forearm, compared to having the arm merely warmed. Emotional pain was created by looking at pictures of the former partner and remembering the breakup, compared to when looking at a photo of a friend.
The fMRI scans showed physical and emotional pain overlapped in the dorsal anterior cingulate and anterior insula, with overlapping increases in thalamus and right parietal opercular/insular cortex in the right side of the brain (opposite to the left arm).
The theory is that the parts of the brain that process social rejection developed by co-opting brain circuits responsible for physical pain. Researchers wrote in the Proceedings of the National Academies of Sciences that, "The current findings substantively extend these views by demonstrating that social rejection and physical pain are similar not only in that they are both distressing, they share a common representation in somatosensory brain systems as well."
Now, researchers are considering the role of different types of emotional pain in somatoform diseases and in fibromyalgia.
Of course, this has been common knowledge for a while. Watch as Nazareth performs their cover of the classic tune, "Love Hurts."