A study done at the UCLA Brain Research Institute shows that the brain can "re-route" certain systems. In this particular experiment, fear was explored. The rats were exposed to cages that shocked them every time they went inside them. This caused them to be scared of them. Once that fear was created the researchers turned off their fear mechanisms and exposed the rats to the cages one ore time. They were surprised to find that they still showed pretty normal fear responses.
I found this study to be quite interesting because it shows just how versatile the brain is. It's pretty amazing to know that our brains have certain "back up" systems in place in case something goes wrong. I don't think that this can be done for everything. I would not be surprised if this only proves true in the most basic and primal of instincts since those are the ones that we have needed since the beginning of time. It would make a lot of sense if our brains had figured out a way for us to do certain things even if the primary system has been affected.