Drakodan Posted:

Actually, a monkey’s head was removed and transplanted onto another one’s body once, and they managed to wake it up. It was paralyzed from the neck down, but responded to them by snapping at their fingers with its teeth and following them with its eyes. It was clearly alive, just paralyzed. It didn’t survive for very long though.

Afraid I have no source, but I did read about this once.

Sounds to me like they managed to hook up the blood vessel connections to keep the brain alive (at least for a while), but not the nervous connections to give it control of the body.