How sleep deprivation can affect memory
We all know the feeling of running on fumes after a night of little to no sleep. However, sleep deprivation doesn't just feel terrible: It can also hinder your ability to form and recall memories.
Even just one night of less than six hours of sleep can affect your short-term memory the next day, said Dr. Richard Castriotta, a sleep medicine specialist at Keck Medicine of the University of Southern California. Not everyone responds to sleep deprivation in the same way, but in general, the longer you go without adequate rest, the greater the burden on your brain. Extreme sleep deprivation – being awake for 24 hours or more – can even trigger people to act out as if they are drunkhe said.
“When we don't sleep,” says Dr. Indira Gurubhagavatula, a sleep specialist at Penn Medicine, “we are aware that we will have difficulty remembering things the next day: 'Where did I put my keys? What's that person's name?'”
While a person rests, the brain strengthens and synthesizes the connections between neurons formed over the past day, which helps store memories – a process known as consolidation. Some researchers think rapid eye movement sleep, or REM sleep, plays a particularly powerful role in retaining memories and helping to process emotions, said Dr. Gurubhagavatula.
“Sleep is not a passive process,” she added.
When people wake up before they are fully rested, they generally get less sleep and may also get less REM sleep, said Dr. Gurubhagavatula. They may also miss the last and longest period of REM sleep, which occurs in the last hours of rest.
That's why “you may find that you can't remember things either,” she said. “You may be a little more tense, irritable, or anxious, but not in your best state.”
If you haven't slept well, you may also have difficulty paying full attention to what's in front of you, making it less likely you'll remember it later. The same goes if you feel emotionally overwhelmed, anxious or preoccupied; your mind is not fully present. This can limit the amount of information our brains encode, says Dr. Sharon Sha, clinical professor of neurology and neurological sciences at Stanford University.
As a result, people may have difficulty remembering details from conversations or events that occurred while sleep deprived. Your brain may not encode where you parked, Dr. Sha said.
A lack of sleep can also lead to what Dr. Sha calls a 'repetition deficit', which may mean that people need an extra push to recall short-term memories. Maybe your brain has stored the details of a meeting you recently attended after a sleepless night, but you need a reminder—the topic of the conversation, or the joke your boss made halfway through—to jog your memory.
Short-term sleep deprivation does not affect more deeply entrenched information known as distant memories, said Dr. Sha. Even when extremely tired, most people can remember biographical details they have known for years, such as the names of the streets they grew up on.
In most people, remote memory is really sharp, said Dr. Sha. “And it's more recent information, or when we were sleep deprived, where we tend to have more problems.”
Getting less than enough sleep is possible negatively influenced the frontal lobe of the brain. It's an area involved in memory retrieval and executive function (a set of skills that includes the ability to multitask and make decisions), said Dr. Michael Rosenbloom, a behavioral neurologist at the University of Washington School of Medicine.
A great study of more than 479,000 adults between the ages of 38 and 73 found that people who said they typically slept between three and six hours performed worse on cognitive tests that measured their executive function than people who slept between six and eight hours. These tests included tasks that involved working memory, which refers to the brain's ability to retain and use a small amount of information remembering the content of a sentence you have just read or what was on your shopping list.
The researchers controlled for age, smoking status and other health factors known to predict cognitive performance. The study found that cognitive performance of those who reported regularly sleeping between three and six hours decreased with each additional hour of sleep missed.
It may take several nights of solid sleep to offset the effects of a bad night, said Dr. Gurubhagavatula. It may become more difficult to recover from sleep deprivation with age, she said, but “we are all vulnerable to this.”