If you feel like hurting your brain, read this article.

Otherwise, maybe just follow these guidelines to happy sleep and learning:
1. don't use alarm clocks
2. don't use caffeine except when waking
3. exercise in bright light when waking to reset your internal clock if you're a night owl, or before bed if you're a lark
4. don't use sleeping pills
5. don't go to sleep unless you feel like you can fall asleep in 5-15 minutes
6. optimal study is early after first waking, and early post-siesta
7. a nap at siesta is good for some
8. listening to tapes while sleeping is worthless
9. alcohol is bad for the brain, but good for the cardio-vascular system (and overall longevity), so 1 drink a day around siesta is probably optimal so as not to interfere with sleep (it will inhibit learning if taken too late)
10. optimal learning concentration has no distractions (even music)

Sleep is, as far as we can tell, a brain process in which memories are re-arranged.  Primarily, short term memories are shifted to long-term by the hippocampus training the neocortex.  You're brain isn't resting when sleeping--it's doing as much activity as if you were taking a SAT.  Dreaming isn't understood well, but is only found in the highest IQ animals, mammals and birds (REM).