Sleep and Memory Consolidation - Do we learn better after a good night of sleep?
Have you ever experienced practising a skill during the day – maybe learning a piano piece or a dance move – and finding that you were better at the routine the next day than where you left off the day before? You may have experienced the brain’s magic trick of consolidating daytime learning during sleep, almost as if your rehearsal continued during your night-time rest.
Memory Consolidation
Memory consolidation is the process by which newly acquired information is stabilized and stored in the brain for long-term retention. Short-term memory – the process that helps us retain information over seconds to minutes – is fragile. Like RAM in our computers, this information store is constantly being wiped so that new data can be processed throughout the day. The process of consolidation helps us to “write” these fragile memories into long-term memory storage, where they can be retrieved and utilized when needed. It is crucial for learning and retaining new skills, facts, and experiences.
Role of Sleep in Memory Consolidation
While consolidation can occur at any time during the day, research has consistently shown that sleep plays a vital role in this process. Some of the most direct evidence comes from experiments on rodents, in which we can directly measure electrical activity in the brain. Scientists have measured the patterns of activity while a rat learns to navigate a maze and observe the same pattern play out while the rat is asleep, almost as if it is replaying a tape of the maze route. This replay process has come to be known as memory reactivation, and it occurs particularly during rapid eye movement (REM) sleep and slow-wave sleep (SWS).
REM Sleep
REM sleep is a sleep stage that predominates in the second half of the night. Characterized by vivid dreaming and body paralysis, it is closely linked to creative problem-solving. Some researchers think that one function of dreams is to connect new information to our existing bank of knowledge, which may explain why people wake up from sleep with insights they did not have when they went to bed. Many artists have also reported finding their muse in dreamland; Paul McCartney famously said that the lyrics to the evergreen “Yesterday” came to him while he was sleeping.
Emotional memories are also processed during REM sleep. During this time, memories that have emotional importance are consolidated. The emotional content of the memories is also regulated, so that we can manage arousing emotions better the following day.
Slow-Wave Sleep
In contrast, slow-wave or deep sleep (SWS), which predominates in the first half of the night, is crucial for consolidating factual information (such as the material you’ve studied for a test), and procedural skills (like riding a bicycle). During SWS, brain waves become large and slow down, allowing neural activity to synchronize across different parts of the brain. This allows memories to be transferred to relevant parts of the brain for long-term storage.
Good sleep benefits memories acquired the day before, but is also an important prerequisite for acquiring new information afterwards. It doesn’t take a scientist to tell you that trying to learn something new and complex when you haven’t had a night of good sleep is no mean feat!
Impact of Sleep on Cognitive Function
Both the quantity and quality of sleep affect many cognitive processes – the operations of the brain that allow us to think, reason, and perform most on-the-job tasks. Scientists began to take this fact more seriously as modern work schedules began to require certain employees to work long shifts that affected their sleep. Accidents and mistakes in industrial, medical, and military settings led to the rise of the field of “neuroergonomics”, or the study of the brain at work. Neuroergonomics researchers became especially interested in using our understanding of psychology and neuroscience to prevent workplace mistakes.
The cognitive facility most affected by sleep loss is sustained attention, which is simply our ability to pay attention to a single task for a long period of time. Reading a book, listening to a lecture, or driving a vehicle are all tasks that require high levels of sustained attention. In fact, most tasks require this facility to some degree. Distraction and lapses in attention are what cause us to misplace our keys, take a wrong turn, or put salt instead of sugar in our coffee.
When it comes to workplace performance and productivity, the culprit to blame is often sustained attention. Neglecting that important detail on a contract or hitting “reply all” on a confidential email may sometimes be chalked up to haste or carelessness, but far more often such unfortunate incidents might have been remedied by a few more hours of sleep. As much as many high-powered executives wish they were, we are not machines. Sleep deprivation does not come without cost, and for those in important positions, the cost may be too high to pay.
Tips to Improve Daytime Cognition
Given the profound impact of sleep on memory and cognitive function, it’s no surprise that prioritizing sleep hygiene and adopting healthy sleep habits can significantly protect and enhance productivity during the day. A large volume of research has shown that on average, next-day performance starts to dip steadily as sleep time falls below seven hours, so a top priority if you need to be your best is to prioritize a sufficient amount of time for sleep.
Once you are getting sufficient time to sleep, another key step to improve daytime cognition is to maintain a consistent sleep schedule: Going to bed and waking up at the same time each day helps regulate the body's internal clock. Studies have shown that regular sleepers perform better academically and at work, so locking in those hours could be just the competitive edge you need!
Finally – and we have discussed this before on our blog – the practice of mindfulness not only helps sleep, but might have benefits for cognitive functioning as well. For example, meditating regularly can lead to improvements in certain aspects of attentional functioning. This is not that surprising since meditating is in many ways a form of training to have better focus and avoid distractibility.
Sacrificing sleep to get that little extra bit of work done may seem like a good prospect in the short run, but it is seldom worth the price you pay for it the next day. In the long term, the downsides to cognition and performance are most certainly not worth the cost. Getting adequate and high-quality rest pays dividends over time for your productivity and cognition – and you’ll probably look smoother on the dance floor as well if that’s your thing!
