The necessary function of sleep is surprisingly complex and little understood. There are literally thousands of studies trying to understand why we sleep. We obviously will not even attempt to go into the details of sleep here. We're just going to provide a few links to sleep and sleep disorders.
Our main purpose is to discuss the differences between natural sleep and anesthesia. Since neither are well understood, the papers can best be described as theories for why anesthesia is different from sleep. There are numerous article on this subject that can only be read either at the library or through a subscription service so the few articles presented here on sleep and anesthesia are just the tip of the iceberg. It will at least get you started if you are really interested.
Another common question patients ask is if they will dream under anesthesia. Here we provide a few links to interesting articles but it is by no means comprehensive.