Jul 24 2014

Sleep and False Memory

When someone looks at me and earnestly says, “I know what I saw,” I am fond of replying, “No you don’t.” You have a distorted and constructed memory of a distorted and constructed perception, both of which are subservient to whatever narrative your brain is operating under.

One of the more dramatic aspects of memory distortion is false memories. These can be completely fabricated memories that are indistinguishable from genuine memories. False memories can involve small details, or entire scenarios. One way to fabricate false memories is with suggestion – just suggesting to someone a detail of an experience they had may cause them to incorporate that detail into their memory of the experience.

The apparent reason for this is that our brains appear to favor consistency over accuracy. Memories are updated to bring them into line with our current knowledge. If we are told that the person was wearing a blue jacket, then our memory might change so that it is consistent with what we now believe to be true.

Psychologists have a number of ways of generating false memories in the lab. One method is to show subjects a video of an event. Then allow them to read a written description of the same event, containing or even just suggesting details that differ from the video. A certain percentage of subjects will incorporate the suggested but incorrect details into their memory. When asked they will “remember” those details in the video.

A new study combines false memory research with the effects of sleep deprivation. It is becoming increasingly clear that sleep plays a major role in memory formation and consolidation. Steven J. Frenda of the University of California, Irvine and his colleagues asked a simple question – would sleep deprivation increase the formation of false memories?

They had subjects view photos of a crime, then read a written description of the crime (with some details conflicting with the photos), and then asked them questions about details. Different groups of subjects had different patterns of sleep deprivation.

Those who were sleep deprived during memory encoding, when viewing the photos, had an increase rate of false memories compared to those who were well slept during memory encoding. There was no difference, however, in performance between well-slept and sleep deprived during the suggestion phase, when reading the written description, or the recall phase, when answering questions.

This is one small study and needs to be replicated, but if it holds up it suggests that the quality of memory encoding is most important to the susceptibility of false memories. It also would confirm Frenda’s suspicion that sleep deprivation would have an adverse effect on memory, but only during the encoding phase.

I have become increasingly interested in the effects of sleep on cognitive function as poor sleep is becoming increasingly common. I see many patients, otherwise young healthy patients, with poor concentration and short-term memory. Normal neurological exam and laboratory testing effectively rules out an underlying disease causing their symptoms. Such patients are then characterized as having a functional dementia (or pseudodementia), meaning that their memory problems are not due to any biological damage to the brain or disease process. Rather, the brain’s function is impaired because it is under some physiological stress.

One common cause of this is chronic sleep deprivation. It’s interesting that most patients will not volunteer that their sleep is very poor, or see the connection to their symptoms. When asked, however, they may report very poor sleep, 5 hours or less each night.

The take-home point is that acute and chronic sleep deprivation can impair brain function. If your sleep is poor, then improving your sleep should be a high priority. Often just some basic sleep hygiene is all that is needed: avoid caffeine, don’t eat or drink right before going to bed, make sure the bed is comfortable, avoid napping during the day, keep the lights low at bedtime, engage in a relaxing activity and then get in bed only when you feel sleepy.

Sometimes a temporary sleep aid is needed. And some patients may have a specific sleep disorder, like sleep apnea, that needs a proper diagnosis and treatment. The bottom line here is that if you cannot fix your sleep with basic hygiene, consult your physician to have an evaluation. Poor sleep should be approached as a medical issue, but often patients don’t come in until they are having secondary symptoms from chronic poor sleep, like memory difficulty.

This latest study adds one more bit of data to the evidence that sleep is critically important for memory formation and overall brain function. Our memories are bad enough when they are functioning optimally. We certainly don’t want them to be compromised further by poor sleep.

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