The brain can be acting analogously to a bratty kid with his hands over his ears refusing to listen to scolding. The animal best known for playing dead is the opossum. It feigns death as a defense against predators since most predators do not feed on dead animals. The opossums are, though, very much aware of their surroundings. They can stay in this inanimate state for several hours if need be.
Frogs can remain so rigid and motionless that even respiratory movements is unobserved.
Very similar to these organisms that are able to induce certain physical aspects for survival, maybe humans are capable of influencing our brains to receive and produce certain signals for our benefit. Many people with conversion disorder have very cavalier attitudes toward this serious symptom and deny any emotional difficulty. Maybe this indifference has to with the fact that this somatoform disorder is not a disorder but rather an adaptive advantage. A possible explanation could be that the human species, before the development of civilizations, used this as a defense mechanism somehow but as time went on and humans learned to dominate over other organisms, there was no need for this technique and therefore became very much like a vestigial organ. Because of this, there seems to be very little that the internist, neurologist, otolaryngologist and ophthalmologist can do.