I rarely sleep on planes. It gives me a chance to see what the mind does without sleep. There are several effects:
1. Increased sensitivity to pain. Little things bother me more. It is as though I were a sofa temporarily devoid of cushions, or a car deprived of suspension. Bumps are more obvious. I am more reactive, and find it harder to ignore discomfort.
2. Higher levels of paranoia. I speculate more on others' motives, on what is happening behind the scenes. I think this is a by-product of lower pre-frontal cortex efficiency. Less able to rationalize appropriately, I float through more theories, but with less certainty.
3. Reduced ability to eat and sleep. It is a descending spiral. The body has fewer of the chemicals that promote an easy metabolism, so it becomes less normative and more erratic.
In contrast, when I caught up on sleep with a glorious long session of dreams and relaxation, these effects reversed. In particular, a good sleep seems to smooth the relationship between immediate experience and long-term memory. Good dreams reconcile the irreconcilable, and allow concepts to sit more easily with each other. It does this by finding undiscovered conscious relationships between matters that were previously unsettled in the unconscious. It is the mind's equivalent of a grand conference, where ideas are aired and explored. A form of semantic democracy, promoting greater integration and harmony. In this way, sleep is a little miracle that sets the world to rights.