The specific region of the brain that helps to form new memories is called the hippocampus. Most memories formed here will be lost during the day, but sleep allows for memories to become more stable. During sleep, the brain cycles through different levels of sleep. These levels will be covered more in depth later. Dr. Robert Stickgold of Harvard Medical School says that ‘sleep seems to be a privileged time when the brain goes back through recent memories and decides both what to keep and what not to keep.” In Figure 1, it is noted that the hippocampus has less brain activity when a person is sleep deprived. On the other hand, hippocampus activity is much higher in those who are well rested.
Stages of sleep
The stages of sleep that we cycle through are categorized as non-REM and REM sleep. REM stands for rapid eye movement, and this stage is where dreaming most often happens. On the other hand, non-REM sleep is thought to prime the brain for new learning. Like mentioned before, the hippocampus is important for making new memories. And, when a person is deprived of sleep, the hippocampus is negatively affected, making it hard to form new memories. Sleep scientist Dr. Walker says that “you can’t pull an all nighter and still learn effectively.” New memories are formed while we’re awake, and are strengthened as we sleep.
Rapid eye movement (REM) sleep- rapid, low voltage theta waves, muscle atone
Non-REM sleep- slow wave, low frequency, large amplitude delta waves
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The science of sleep
Memory consolidation depends on Ca2+ activation of the cAMP/MAPK/CRE-mediated transcriptional pathway and protein synthesis. This pathway, as well as protein synthesis, undergoes a circadian cycle, a 24-hr cycle that responds to light and dark. If this process is disrupted in any way, memory formation decreases. REM sleep also activates this pathway which goes hand and hand with circadian cycles. Memories formed with the help of the hippocampus are maintained by reactivation of CREB-mediated transcription and protein synthesis during circadian cycles that occur during REM sleep. These events are all made possible by cAMP activation of the MAPK pathway. This pathway is pictured in the figure below and can be referenced more in depth in the article Role of circadian rhythm and REM sleep for memory consolidation.
So, how do you get better sleep?
After reading this post, you may ask yourself what you can do to get better sleep? The answer is that there isn’t an exact answer, but there are plenty of things that can be done. Better sleep is correlated with better eating habits, and better physical health. The CDC has a great schematic for how much sleep a person needs based on their age. They also mention multiple tips for improving sleep; go to bed at the same time each night and wake up each morning at the same time, keep your room dark and quiet, avoid alcohol and caffeine before bedtime, and be physically active every day.
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References
Memory consolidation and sleep- PubMed
Sleep on it- how snoozing strengthens memories
