Consolidation, creativity and calm – find out why a good night's sleep is essential for learning and memory.
Imagine it's the night before an exam...
Do you: A) get an early night, or B) stay up late for some last minute revision?
For many of us, the desire to cram a few last-minute facts into our heads may seem tempting, but in reality, putting the textbook away and allowing ourselves a good 7-9 hours of shut-eye is the best thing we can do to enhance our learning and memory.
You can think about the impact of sleep on learning and memory in two key ways:
Sleep Before Learning
Firstly, if we aren't well slept, our ability to focus and take-in new information is limited. This is because sleep deprivation significantly effects the functioning of our Pre-Frontal Cortex (PFC) – an area responsible directing attention, preventing distraction, maintaining focus, switching tasks and making decisions. Incidentally, a subconscious acknowledgement of this can be seen in the phrase 'sleep on it' – it really is best to be well-slept before making a big decision!
Indeed, brain scans have shown that one night of sleep deprivation can reduce the activity and functional connectivity of the PFC, resulting in problems maintaining concentration and taking in new information – not a good combination if we are aiming to learn!
Additionally, if we are not well slept, the hippocampus – our short-term memory store – remains cluttered with yesterday's information. Without sleep, the memories in this short-term store do not get consolidated and transferred into longer-term storage areas, meaning our memories become susceptible to decay and interference (in other words, they get lost). Furthermore, as the short-term store is already full, our capacity to take-in any new information is also greatly reduced.
Lack of Sleep After Learning
Poor sleep after learning can also pose significant problems for memory.
During NREM (non-rapid eye-movement) sleep, we see information in the hippocampus getting reactivated, transferred and integrated into the neocortex – our long-term memory store. Like a super-organiser, the sleeping brain cleverly prioritises the new and important information (i.e., what you learnt in class), while any redundant information (i.e., what you had for dinner) is forgotten.
Importantly, this process isn't a one-hit-wonder. While improvements in learning and memory can be seen after a single-night of good sleep, memory performance actually continues to improve with more consecutive nights of good sleep. This is why consistency is key when it comes to sleep, and why repetition of learning material really can help 'get things into your head'.
Sleep not only strengthens our memories, but it also looks for associations between new information and old information. In this way, sleep provides us with a constantly updated and revised version of the world, and helps us to understand connections between various concepts when we are awake.
Interestingly, during REM (rapid eye-movement) sleep, the brain seems to make associations between weakly related concepts – the kind of associations that may result in weird and wonderful dreams. Sometimes these weakly related associations can help spark moments of creative genius upon waking. Indeed, numerous inventions (the sewing machine), Nobel Prize-winning ideas (the structure of DNA), works of fiction (Mary Shelley's Frankenstein) and famous songs (John Lennon's Imagine) have been attributed to dreaming, and are most likely to have occurred during the REM state.
Emotional Learning and Memory
As well as making associations, REM sleep is also important for regulating the emotional tone of our memories.
Whenever we experience a negative event, there will be some level of associated negative emotion. During REM, the brain exists in a neurochemical state of low arousal and stress, which is thought to help decouple – or unpair – the emotion from the memory. Consequently, when we recall past events, we are not subjected to the same level of emotional intensity that we may have experienced at the time.
Interestingly, there is also evidence to suggest that those individuals who dream about their waking problems, are better able to cope with them in the future.
Sometimes, when events are extremely traumatic, our brains may not be able to achieve the low levels of arousal and stress needed for this process. In this case, the brain may repeatedly fail to decouple the emotion from the memory night after night – something that is best illustrated by the recurrent nightmares afflicting those with Post-Traumatic Stress Disorder (PTSD).
Whether it's setting us up for a day of learning, helping us to consolidate information, providing us with a spark of creative genius, or allowing us to calmly recall old memories, it is clear to see that sleep is essential for learning and memory.
The answer is always A!
References
Cartwright, R. D. (1991). Dreams that work: The relation of dream incorporation to adaptation to stressful events. Dreaming, 1(1), 3.
Lipinska, G., & Thomas, K. G. (2018). 0088 Sleep-to-Remember, Sleep-To-Forget: Examining Emotional Memory and Emotional Reactivity in PTSD-diagnosed Participants. Sleep, 41, A36.
Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437(7063), 1272-1278.
Verweij, I. M., Romeijn, N., Smit, D. J., Piantoni, G., Van Someren, E. J., & van der Werf, Y. D. (2014). Sleep deprivation leads to a loss of functional connectivity in frontal brain regions. Bmc Neuroscience, 15(1), 1-10.
Walker, M. P., & van Der Helm, E. (2009). Overnight therapy? The role of sleep in emotional brain processing. Psychological bulletin, 135(5), 731.
Walker, M. (2017). Why we sleep: The new science of sleep and dreams. Penguin UK.
Zadra, A., & Stickgold, R. (2021). When brains dream: Exploring the science and mystery of sleep. WW Norton & Company.