Recent research in the University in Germany that studies sleep and it's impact on learning and memory found that your learning cycle is strongest during non-REM sleep.
They taught people and gave them a cue... a pleasant smell. They gave a burst of the smell during the subjects sleep cycles and watched what happened in the brain. The same neurons started firing that they were using during learning. They found the brain was more responsive during non-REM and follow up testing indicated that those who had the smell cued during that time did better than those who received the cue during the REM cycle. The test had something to do with memory.
Sorry I read this late last year and that what I remember about it. It's interesting but useless in the sense you need to be in a lab to check you are cuing yourself during a non-REM cycle. So I'm not going to hunt for it for you. While I probably saved the bookmark I discovered backing up your computer doesn't help much with certain software. [The side effects of manifesting something within 24 hours of having the thought I'd really like to upgrade to a faster computer]
Alex
