Some anesthesiologists believe that, but there's really no solid evidence for it. The reality is that no one really knows how or why anesthetics work, we just know what generally does work. I was told this by an honest doc, who also told me this scary fact: Because it's best to minimize the drugs that put you under (especially gaseous), and b/c we're getting better at walking that line, it's increasingly common to have patients wake up and freak out at the sight of their chest spread open. That's why the anesthesiologist keeps a couple of loaded syringes on the cart ready for emergency use: one is an instant paralyzing agent, the other a powerful memory blocker.