Sleep is not recovery after learning — it is the completion of learning. N3 slow-wave sleep consolidates declarative facts via hippocampal sharp-wave ripple replay. REM sleep integrates new memories with existing knowledge and generates insight. The final two hours of sleep are peak REM. A 6-hour night removes these hours disproportionately. Stickgold documented 40 percent recall improvement from adequate versus poor sleep on identical learning protocols. The most important study decision is not what you learn — it is what follows the learning session.