The Phantom Limb Syndrome fascinated me because it was an example of one sensation triggering a seemingly irrelevant perception. This was specifically caused by the brain's plasticity, which is the brain's way of efficiently allocating its resources. Regularly plasticity occurs as the brain learns and grows, but it may occur from damage too. This explains how individuals function when a genetic variation introduces a new appendage to the genome. In the case of the phantom limb, the brain saw wasted resources that were previously allocated to the lost limb, and reallocated them to the cheek. This lead to perceptional confusion as the brain was already conditioned for a "normal" human being.
I'm specifically curious about plasticity mid-life that deals with entire senses. While I have no doubt that a deaf person will reallocate the part of their brain that processes sound to do something else, I'm not sure that the extra resources will go to another sense. Does plasticity cause people who go deaf to hear Mozart when they taste salt? I've heard of cross-sense relationships before, but never in an educational or real-world setting. The first time, it was in a game called "The Color Tuesday" where the protagonist could "see" the colors of words. The next was in an article on Cracked that mentioned "Synesthesia". I don't consider either source to be reputable, but at the very least, synesthesia does exist on Wikipedia.
The article did not explain how synesthesia works, so I cannot be sure that it is in any way relevant to plasticity. If it is relevant, what causes people with undamaged senses to remap their brain in early development, and if it is not then what happens when an entire sense is lost? There is a world of difference between having the part of the brain that dealt with touch in the hand get taken over by touch the cheek and having the part of the brain that dealt with sight get taken over by smell. Due to the lesser degree of similarity between different senses, will plasticity work differently at such an extreme, and if so what are the likely results?