Is the Brain Doing the Equivalent of Back Propagation?

On modeling the algorithms of the brain, Boltzmann machines seem to come close. The field shifted to back propagation because it was so much more efficient. It's pretty clear that the brain doesn't do back propagation. Well, you know, it's doing something that may be equivalent. How could the brain do it? You're right, it's not going to do the same algorithm, but there are feedback connections and feed forward connections in this hierarchy. But nobody knows what information is being carried. And so now it gives us a hypothesis. Let's go in.