Reminds me of a chapter in Cardinal of the Kremlin by Tom Clancy.

Sensory deprivation is a very easy way to induce a trancelike or hypnotic state without chemical enhancement. There are all kinds of uses for it including certain "alternative" practices. I tried it once for insomnia and it made it much worse, go figure. It is very good to bring your blood pressure down if that is affected by stress.

I can see how it is used for interrogation though, not having the normal visual or auditory indexes about your environment induces panic.

There are people who live in states of sensory deprivation.

What I wonder is if there are some people who come up with techniques that help them maintain function, and what those are.

Or if the natural function of gearing down the brain when much of it becomes unneeded and potentially dangerous to maintain for survival - if there are some people who "boot back up" afterwards, and what it is that they do that boots their brains back up into normal function again.