The Science of Sleep: Wonders of the Resting Brain

I began gathering notes on this subject when I first learned the association between sleep and memory consolidation (converting short term memories to long term). In a time when memory collection and recall is highly regarded one is urged to find ways to maximize the efficacy of these, and so I began my search through books, periodicals, scientific articles, and other materials for ways to become an efficient learner. What I found is nonetheless worth sharing.

Sleep is not only essential for learning and memory but also plays an important role in a large number of biological processes. In the past 20 years neuroscientists have learned the importance of sleep regarding the workings of the immune system, hormonal balance, emotional and mental health, and just lately the clearance of toxins from the brain. We know that melatonin, a hormone derived from serotonin and secreted by the pineal gland, is responsible for circadian rhythm regulation. The pineal gland, located in the epithalamus, is very active early in life secreting vast amounts of melatonin (ergo the reason why babies sleep a lot) and atrophies as we age. Melatonin is also an effective antioxidant protecting the nerves of the central nervous system against oxidative damage from toxins, also known as free radicals. Most people have heard of melatonin as a treatment for jet lag; these pills are sold over-the-counter in the U.S. but in some parts of Europe they are sold under prescription. It is important to mention that light inhibits the production of melatonin, so if sleeping quality is your endeavor, you must know that avoiding bright lights from electronics and other sources induces sleep.

The sleep cycle takes approximately 90 minutes. It cycles through three stages of sleep and a REM (Rapid Eye Movement) phase before restarting. Each sleep cycle is characterized by wave frequencies measured through electrodes in a piece of equipment called an electroencephalogram or EEG. For discussion purposes we will only mention stage 3, also known as slow-wave sleep, and REM. In a recent publication, The Secret World of Sleep, neuroscientist Penelope Lewis states that these two sleep stages are inversely related, that is, if one is long the other is short and vice versa. She goes on to explain that people who experience more stage 3 and less REM report feeling better rested than their longer REM counterparts. Most of us have heard that dreams occur during REM, which is true, as the night progress dreams become more fragmented and bizarre, the most emotional dreams, the ones we are most likely to remember, occur during REM. But spending more sleepy time in REM is also associated with feelings of tiredness, negativity, and depression, similar to what sleep deprive individuals and narcoleptics experience. One of the most interesting findings involves the neurotransmitter we mentioned earlier, serotonin. Too much serotonin inhibits REM while too little leads to excessive time spend in REM. As you are probably aware low levels of serotonin are associated with depression and anxiety and treatment often involves a group of drugs known as: selective serotonin reuptake inhibitors (SSRIs). Simple ways to increase levels of serotonin are: exercise, yoga, and foods like chicken, fish, and soy products.

So what about memory consolidation? The current theory states that memory consolidation is initially coded in the hippocampus but gradually transfers to the neocortex; this gradual projection between these two structures is inhibited by acetylcholine. Since acetylcholine is at an all time low during sleep stage 3, scientists speculate that memory consolidation occurs during this stage. So yes, a good night sleep along with rigorous studying and repetition strengthens the neuronal pathway of specifics memories allowing consolidation and faster recall. The recommendation of “sleep on it” is actually accurate.

One of the most astounding findings took place in 2013 at Dr. Lulu Xie’s laboratory at the University of Rochester Medical Center. In brief, Xie found that cerebrospinal fluid (the liquid that surrounds the brain and spinal cord) besides its shock absorbing properties also serves to remove free radicals out of the brain during sleep. As you may recall, earlier we mention melatonin as an effective antioxidant that removes toxic molecules to avoid damage. Xie performed a clever experiment where she injected beta-amyloid to rats and observed the rate of removal in sleep vs wake. She found that the cellular space in the brain expands allowing more CSF to percolate into brain tissue and through careful measurements found that the rate of removal was twice as fast in sleep vs wake. Neurologist Richard Cytowic says the brain, which accounts for 2 percent of total body weight, can densely pack 86 billion neurons and consume about 20% of total daily glucose in adults, 50% in children, and 60% in infants. We know the brain lacks storage for glycogen and consumes a lot of it, in fact the brain consumes an astounding number of ATP (3.4 x 10²¹ molecules of ATP/minute) to maintain itself. At any one time only 1% to 16% of neurons in the brain are active, more than this and the energy expenditure would be unsustainable, but the brain is smart and it relays the most amount of information using the least amount of neurons, this is known in science as, sparse coding. I know this is a lot of information but what I am trying to get across is that waste products are generated at the same rate as energy is used and sleep is absolutely necessary to facilitate the process of waste management.

I will close with the nap vs. no nap dilemma. In his book Brain Rules molecular biologist John Medina dedicates an entire chapter to propose napping in America. Medina describes a plethora studies in which participants were found to perform better in different tasks after a nap. He proposes 30-45 minute nap times in what he calls the nap zone which takes place some time in the early afternoon. If you are strategic about memory consolidation, then studying or rehearsing the target material right before you nap is a great idea, memories are likely to be replayed during your snooze optimizing consolidation. It is important to mention that if you are experiencing nighttime sleep problems then napping might just worsen the situation according to the Mayo Clinic. In conclusion, most professional agree on 7 to 8 hours of sleep per night, remember “sleep well, think well.” so adjust accordingly!

Lastly, this is a list of suggestions on how to get a good night sleep as found in Penelope Lewis latest book, the list includes:

1. Psychology - The way you feel about your bed and bedroom is important. It should be comfortable, not brightly lit, with fresh air, and strongly associated with sleep, that means one should avoid watching television or using electronic devices in bed.
2. Temperature - As a rule of thumb your room should feel cool. Enough to help your body cool down. A warm bath an hour before sleep helps your body accomplish this faster. If a bath is not possible, than a hot foot bath can help too.
3. Light -Avoid blue light. This is the light you experience during day time. Unfortunately, televisions, computers, and smart phones emit this kind of light. Exposure will reset you circadian rhythm. You can use an orange filter if you insist on using your phone. Your room should be pitch black.
4. Sound - Avoid loud sounds. Some studies have shown evidence that low intensity pink or white noise dull the impact of external sounds, that could be otherwise disturbing.
5. Smell - Your bedroom should feel fresh with plenty of clean air. Avoid perfumes or air fresheners (jasmine, lavender, and valerian) there is scant evidence to support them. Only a handful of studies show that a faint scent of valerian could promote sleep.
6. Food - Some sleep promoting foods are: chamomile tea, warm milk, plain yogurt, honey, potatoes, bananas, tuna fish, cottage cheese, oats, almonds, flax seeds, peanut butter, low fat cheese, tofu, whole-wheat bread, and sun flower seeds. Avoid heavy meals prior to sleep and foods with tyramine (papers, smoke meats). Caffeine should be avoided after 4 in the afternoon.

These are some of the most important points I came across while researching sleep. This information is a compilation of books, articles, and videos. If interested in any of the topics I presented you can email me by pressing the “say hi” button at the bottom of this page, I will gladly provide you with the sources. As always if you liked this blog leave you kudos, subscribe, and share the information. I will now depart to enjoy some nighttime cleaning and consolidation in a place call stage 3! See you all next time.

Mounir C. Cejin