Sleep and Memory: What Research Says About Studying and Rest

What the review says, in plain words

Diekelmann and Born (2010) reviewed research on how sleep relates to memory. They describe sleep as a state that can optimize the consolidation of newly acquired information, depending on the conditions of learning and the timing of sleep. Consolidation means the processes that help new information settle into longer-lasting memory.

The review describes two kinds of sleep, slow-wave sleep (a deep stage) and REM sleep, as supporting different consolidation processes: system consolidation and synaptic consolidation. During slow-wave sleep, it describes memories that depend on the hippocampus (a brain region involved in memory) being reactivated and redistributed to other brain areas. For a student, the main idea is simple: what happens after a study session, including sleep, may be part of how new learning is consolidated. For the three-step overview of memory, see how human memory works.

What the review's abstract does not say

• No hours. The abstract we read gives no advice on how much sleep to get, so we make no prescriptions.
• No grades. Nothing in the abstract promises better test results from any sleep pattern.
• No study schedule. The abstract does not say whether reviewing before bed beats reviewing at another time.
• Mostly lab research. It summarizes mostly laboratory and mechanism-level work. We read only its abstract.

Those gaps matter, because it is easy to stretch a general review into specific advice that it never gave. When a point below is our own planning suggestion, the table says so.

Planning study sessions around sleep

The ideas below combine the sleep review with two other sources. Carpenter et al. (2012) summarize research showing that performance on final tests improves when study sessions are spaced apart rather than massed in immediate succession. Rohrer and Taylor (2007) found that college students whose math practice was spread across multiple sessions did much better one week later than students whose practice was massed in a single session. The abstracts we read for these two studies do not mention sleep.

The reasoning behind the last row is straightforward. One long session is massed practice, and it leaves no gap for later review. A plan that spreads the same hours over several days gives you both gaps and nights of sleep. Whether that helps you personally is something your own test results will show. For how loss over time was first measured, see the forgetting curve explained.

A simple two-day routine

1. Day 1, study session: learn the material, then close the notes and answer from memory.
2. Day 1, end of session: check your answers and mark the misses.
3. Day 2, first review: answer the missed items from memory before looking at anything.
4. Day 2, check: fix the gaps and plan one more review a few days later.

You can run this routine in the forgetting and sleep practice deck. If you also want a lecture-specific version, see what to do after a lecture, and for the causes behind lost material, why you forget what you study.

Common mistakes

• Quoting a number of sleep hours as if a memory study set it. The abstract we read gives no hours. Leave health questions to a professional and use the research for general ideas only.
• Planning an all-night study session. Spread the same hours across several days. The spacing research we cite favors spaced sessions over massed ones, though the abstracts do not mention all-nighters.
• Studying a topic in a single late session and never returning to it. Add a short recall check the next morning, so one session becomes two.
• Treating sleep as a substitute for review. The abstract does not say that sleep replaces practice. Keep testing yourself on later days.

Frequently asked questions

Does sleep help memory?

A major review describes sleep as a state that can optimize the consolidation of newly acquired information, depending on the conditions of learning and the timing of sleep. It is a review of mostly laboratory research, so it does not promise results for any one student.

Should I study right before bed?

The sources we read do not compare bedtime review with other times. A short recall check in the evening is a reasonable preference. Whether it beats another time of day for you is something you can only test yourself.

How many hours of sleep do I need to remember what I study?

The abstract we read does not say. We make no recommendation. If you are worried about your sleep, talk to a health professional, who can advise you in a way a study guide cannot.

Is an all-nighter a bad idea before an exam?

The sources we cite do not test all-nighters directly. The planning argument is that one long session is massed practice, which spaced research suggests does worse a week later. Spreading the hours is the safer plan.

Sources

We opened each source below before citing it. See Methodology and Sources for how we check them.

1. Diekelmann, S., & Born, J. (2010). The memory function of sleep. Nature Reviews Neuroscience, 11(2), 114-126. Open the source
2. Carpenter, S. K., Cepeda, N. J., Rohrer, D., Kang, S. H. K., & Pashler, H. (2012). Using Spacing to Enhance Diverse Forms of Learning: Review of Recent Research and Implications for Instruction. Educational Psychology Review, 24(3), 369-378. Open the source
3. Rohrer, D., & Taylor, K. (2007). The shuffling of mathematics problems improves learning. Instructional Science, 35(6), 481-498. Open the source
4. Roediger, H. L., & Karpicke, J. D. (2006). Test-Enhanced Learning: Taking Memory Tests Improves Long-Term Retention. Psychological Science, 17(3), 249-255. Open the source