The prefrontal cortex is where your logic mainly happens, when you sleep it is deactivated normally which is why you don't think about giant, angry, rainbow, flying, supersonic hot dogs being abnormal. And when lucid dreaming occurs the prefrontal cortex is reactivated a little which is why you can think normally and be conscious when LDing. Your subconscious seems to think logically also so I guess if it is a real thing, it'll reside all over your prefrontal cortex.