Can You Touch Your Jaw and Feel It in Your Hand?
"Phantom limb" phenomena have been well-known since at least the time of Descartes. People with missing limbs will report feeling sensations in the missing areas. In 1998, V.S. Ramachandran famously showed that people with missing arms can sometimes be induced to feel phantom sensations (as though in their missing hands) if gently stroked on the face. (See this article, for example, which is rich with interesting descriptions.) The reason for this, evidently, is that as the nerves from the phantom limb area provide no useful input, other nearby regions of the brain begin to recruit neurons from the areas formerly dedicated to input from the phantom limb; and the primary cortical region associated with tactile input from the face is adjacent to that associated with tactile input from the hand. Apparently, plasticity in input can sometimes outrun plasticity in the felt sensation, so that the relevant neurons that used to respond to stimulus from the hand and trigger (appropriately) a sensation subjectively located in the hand can come to respond to stimulus from the face while still triggering (now inappropriately) a sensation subjectively located in the hand.
Recent research -- for example by Peter Hickmott here at UC Riverside -- has shown that in animals whose nerves have been cut, one can start seeing neural plasticity within minutues. Cortical neurons near the border between forepaw and jaw which formerly acted in synchrony with other forepaw neurons start to act in synchrony with the jaw neurons.
This leads me to think of the following experiment. If we somehow induced in people cortical input from the hand similar to that one would get from denervation of the hand (by sensory deprivation? by anaesthesia?), and then one gently stroked the jaw, a la Ramachandran, might the person report a sensation in the hand?
If this has been done, I haven't heard of it.