Kruger, Kruger... there is a hypothesis that during sleep, the brain switches from the senses to internal biochemical processes and regulates the work of immunity, digestion, hormones and much more. That is, in order not to sleep, we would need a separate brain just in order not to die from the rejection of all drinks. Regular, daily adjustments of all "system services".
And the relatively recently formed part responsible for consciousness, in the best traditions of “You Wrongly Write Animals” remains foolish. She is stupid all night and, locked in herself, sees all sorts of glutes called "sleep". Only the most necessary thing was formed - disconnecting from the "executive mechanisms", so that the branch did not sneak in a dream, erasing the memory, so that he did not go too deep into his glutes and did not forget to catch the mammoth, and so on.
If this hypothesis is true, all this potential can really be used, instead of connecting the rest of the brain in the dream to an external device. "Ancient parts" are engaged in the arrangement of the body, and the consciousness at the nearest compact codes the solution of a system of differential equations.
Sometimes we succeed in doing so, if in a dream we have focused on something, and in the morning with surprise found that the decision is right, not nonsense!