Harvard Health Blog
Want to improve your memory? Get a good night's sleep!
There are few things that are as beneficial for your memory as having a good night's sleep. Let's understand why.
If you're tired, it's hard to pay attention, and memory requires attention
To remember information, you need to pay attention to it. If you're tired, you simply cannot pay attention as effectively as you would if you were well rested. That statement seems straightforward, but it brings up another question: why do you get tired?
You may feel tired and have trouble paying attention either because you've been awake too many hours and sleep pressure is building up, or — even if you've had a nap — because it is the middle of the night and your circadian rhythm (your internal clock) is telling you to sleep. In either case, you'll you have trouble paying attention, and thus trouble remembering.
Does caffeine help?
Caffeine blocks chemical receptors in your brain so that, temporarily, you cannot feel the sleep pressure. Thus, caffeine can enable you to be more alert, be more attentive, and remember better. But as you probably know from your own experience, caffeine can only delay the mounting sleep pressure, which eventually leads to overwhelming tiredness.
Get ready for new learning
When you learn new information during the day, it is temporarily stored in the hippocampus, a seahorse-shaped part of your brain behind your eyes. The hippocampus has a limited storage capacity. If you exceed it, you may have difficulty adding new information — or you may actually overwrite an old memory with a newer one.
Fortunately, that doesn't usually happen. Each night while you sleep, the connections between neurons (called synapses) shrink to reduce or eliminate the memories you don't need — such as what you ate for breakfast last week and the clothes you wore yesterday. This selective pruning of synapses during the night prepares you to form new memories the next day.
Sleep to consolidate memories
Sleep also helps us consolidate the memories we want to preserve, transferring them from transiently accessible memories to those that can be recalled years later. Memories for facts and skills both show greater retention over a 12-hour period that includes sleep versus a 12-hour period while awake. Much of this consolidation occurs during stage 2 sleep, a light sleep phase that occurs most in the hours prior to awakening. This means that if you get up early without a full night's rest, you may be impairing your ability to hold onto your memories.
Interconnect your memories while you dream
Although you dream in several stages of sleep, your most interesting and vivid dreams usually occur during rapid eye movement (REM) sleep, so-called because while your eyes are moving rapidly, your body is otherwise paralyzed. It is during REM sleep that your newly consolidated memories become interconnected with your prior memories, including those of your life as well as your library of facts and knowledge. This connection between your recent memories and your prior memories and knowledge is one reason that you may wake up with a new and valuable perspective on a problem — or perhaps even a complete solution!
This actually happened to Dmitri Mendeleev, who was struggling for months with how the atomic elements should be placed in the periodic table. In a dream on February 17, 1869, he glimpsed where all the elements belonged and, after writing down what he dreamt, found only a single, small correction was needed.
You'll feel better in the morning
Have you ever been terribly upset about something and, by the next day, it felt at least somewhat better? Sleep can also strip off the emotions related to painful memories while still retaining the memory content. Thus, you'll be able to remember what upset you without having to relive the full emotional intensity of the event.
Do sleeping pills help?
Melatonin isn't a traditional sleeping pill, but it can help regulate your sleep cycle if that's the problem. Acetaminophen can relieve little aches and pains that can keep you up at night. All other sleeping pills, however, whether prescription or over the counter, sedate you and actually make your memory worse, both for what you learned earlier that day and what you're trying to learn the next day! Nonpharmacological treatments for sleep are by far the best.
The bottom line
Want to maximize your memory whether you are studying for an exam, preparing for a client meeting, or looking forward to your 50th reunion? You'll be more likely to remember the information for the exam, the documents for the meeting, and the names you're reviewing of your classmates if you go over the material you wish to remember daily for several days, each followed by a refreshing seven to nine hours of sleep each night. Sleep well!
About the Author
Andrew E. Budson, MD, Contributor; Editorial Advisory Board Member, Harvard Health Publishing
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