There's been a fair amount of press about a new paper in Science that shows how the brain responds to social rejection. The kicker is that a region of the brain known as the insula becomes active. As I mentioned yesterday, that's the same area that responds to pain and physical distress. It's an interesting paper with historical dimensions that are missing from the news reports--historical in both the human and evolutionary sense. There's a lot of back-story behind the word "heartache."
A common theme in evolution is the way a structure or a system takes on new functions over time. In our "reptilian" ancestors, bones in the jaw were co--opted for conducting sound to our brains; over a couple hundred million years they've evolved into our middle ear bones. A lot of evidence now suggests that human feelings were built in a similar fashion on top of more ancient systems for sensing the state of the body--pain and distress for states that are dangerous to an animal, pleasant ones for states that are good. Disgust is an ancient response that keeps many animals away from bad-smelling food; some evidence suggests that we are morally disgusted by bad behavior, we borrow some of the same circuitry. The new paper on rejection suggests how the basic pain response took on a social dimension in humans.
This overlapping circuitry may have helped produce the strange concept of heartache. It may be metaphorical now, but originally it was supposed to be a purely physical description. From ancient Greece to the Renaissance, a strong tradition held that the heart contained a soul of its own that could perceive the outside world and produce feelings. Great thinkers from Aristotle to Thomas Hobbes were convinced that nerves delivered their signals to the heart rather than the brain. With the birth of neurology in the 1600s, the brain came to take a central place in the body and was the site of emotions and perceptions. Meanwhile, the heart was de-souled, transformed into a mechanical pump.
But the tradition of the heart lives on, and not just in words like heartache. Think for a moment of all the images of Jesus with an open heart. You never see him pictured with an open brain.