Here's something I wonder about.

In synesthesia, a part of the brain which usually does one task gets involved in another. For example, color is supposed to be handled by one set of nerves, music by another. Yet to me, the song "The Hills are Alive with the Sound of Music" is maroon in color - dark and somber. The color and sound nerves are intermingled.

Now. Let's take the case of schizophrenics who hear 'voices' when no one is speaking. The voices are in their own heads. Are their brains taking non-speech stimuli and turning them into voices? Does a squealing brake, a noisy fan, a flickering light or a strong smell turn into a voice for them? If so, can we weaken the voices by giving the schizophrenic a more peaceful environment?

Can they learn to discount the voices once they learn where the voices come from? Can they say, "You're nothing but the buzzing of the refrigerator!" and so gain some peace of mind?

I have no idea how to research this, but I think it's a good question.