You may have noticed that if you haven’t slept well, the next morning you’re more likely to forget your keys, forget your umbrella, or have one of those little incidents that make you exclaim, “Where are I going?” I ?
Sleep is essential for general human health, but especially for brain health. The first-century Roman author Quintilian already observed that “a single night’s sleep would greatly increase the power of memory.” Throughout the 20th century, scientists discovered a correlation between memory ability and sleep duration and, conversely, forgetfulness and sleep loss. In the 1960s, paradoxical sleep, in which dreams take place, was discovered and from the beginning it was understood that this phase of sleep had a great influence on memory.
How memory works
Sometimes we think that memory is like a videotape file that we can play whenever we need it, but nothing could be further from the truth. Memory in the brain works through the interaction of different areas responsible for storing, consolidating and retrieving information, as well as forgetting what we don’t need.
During the day, the brain receives a large amount of information from the senses that is temporarily stored in the hippocampus, the structure responsible for the formation of short-term memories. For example, when we remember a street number to go to, or what we ate the night before, things we forget shortly after.
Repetition strengthens bonds, but sleep is essential for the consolidation of memories, that is, their transition from short-term to long-term memory.
The cerebral cortex is responsible for storing long-term memory, like those poems we learned by heart in school and still remember. When we learn something new, neurons connect through synapses and these connections can be lost or strengthened. Repetition strengthens bonds, but sleep is essential for the consolidation of memories, that is, their transition from short-term to long-term memory.
There are several types of memory: declarative memory, which involves facts and events, and procedural memory, which refers to motor skills. Sleep, especially deep stages like REM sleep and deep slow-wave sleep, is when the brain reorganizes and stores information from our memories. Throughout life, the brain continues to create and strengthen neural networks that allow us to remember and apply what we have learned.
Dr. Verónica Giménez de Béjar, head of the Neurology Unit at Clínica DKF, explains that “it is a complex biological process linked to cerebral and extracerebral functions, relevant at all stages of life.” “In childhood due to the need to process more information and stimuli associated with development, in adulthood for the use and expansion of information and in older adults due to increased risk neurodegenerative diseases,” he explains.
Dream and memory
During sleep, and particularly during deep sleep or slow-wave sleep (SWS), the brain repeats the activation of neurons that have received recently learned information. This process of rehearsal is considered essential for transferring memories from short-term to long-term storage.
This transfer of memories, called systems consolidation, allows memories of the day to become more stable and to integrate with existing knowledge, that is to say with other memories that we have already consolidated.
Sleep also promotes neuroplasticity, which is the brain’s ability to create and eliminate connections between neurons. Therefore, during sleep, important synaptic connections are strengthened and unnecessary ones are removed.
Processing emotional memories
So what are dreams for? Dreams occur in different phases of the sleep cycle, but especially in the phase called REM (rapid eye movement). Unlike deep sleep, in this phase the brain is very active, just like during wakefulness, however, the body is paralyzed except for the eyes, which move following the action contained in dreams. This makes sense, since the same brain circuits that we use to move when we are awake are reactivated, and if this paralysis did not occur, we could move and suffer an accident.
During REM sleep, declarative memories are not consolidated, like today’s math class, but rather emotional and procedural memories. In this phase, emotionally charged experiences are reactivated, which is why in our most vivid dreams we may feel fear, shame, joy or sadness. This is very important for regulating our emotions during the day and mitigating the negative impact of these emotions. Different studies have proven that when REM sleep is lost due to insomnia, people have difficulty controlling their emotions and behavior, as well as recognizing the emotions of others.
How Lack of Sleep Affects Memory
Sleep deprivation, even mild or moderate, can interfere with the brain’s ability to carry out these fundamental processes. Different studies have shown that a night of insufficient sleep affects the ability to form new memories, because the hippocampus, which acts as a kind of repository for short-term memory, functions less efficiently. Research using magnetic resonance imaging has shown that the hippocampus of sleep-deprived people has reduced activity and, moreover, decreases in size over time.
Sleep also protects our memory against what is called retroactive interference, which is the tendency of our brain, when we learn something new, to make it difficult to remember what we previously learned. Sleep helps us remember both the new and the old.
A study published in Nature concluded that sleep also facilitates the reorganization of memories, improving our ability to access relevant information and combine different information, new and old, to solve problems. Without adequate sleep, not only memory but also logical reasoning suffers.
When insomnia affects REM sleep, it is emotional memory that suffers. Its interruption can distort the way we process and remember emotionally charged experiences. Some studies indicate that sleep-deprived people tend to remember more negative details of their experiences, which would be counterbalanced by sufficient REM sleep.
It is logical to think that the more chronic a sleep problem becomes and the duration of sleep shortens, the more likely it is that memory processes will be affected.
Veronica Giménez de Béjar
— neurologist
In the long term, the effects of sleep deprivation on memory can be cumulative and serious. Lack of sleep is closely linked to the development of neurodegenerative diseases, such as Alzheimer’s disease. During sleep, especially deep sleep, the brain removes metabolic waste products, such as beta-amyloid and tau proteins. Sleep deprivation hinders this “cleansing” process, leading to a toxic buildup of these proteins, accelerating neuronal damage and cognitive decline.
How much sleep should we get to avoid this memory damage? Dr. Giménez says this is a “difficult question to answer.” “They contribute to the balance between the different phases of sleep, their duration and the number of sleep cycles, so that these biological changes are triggered.” The danger is not a sleepless night, but a constant lack of sleep. “It is logical to think that the more chronic a sleep problem becomes and the duration of sleep decreases, the more likely it is to affect memory processes and other related problems such as waste accumulation.”
* Darío Pescador is editor and director of Quo Magazine and author of the book the best of yourself Published by Oberon.
