La_Boheemienne_endormie

by Fernanda Ferreira
figures by Krissy Lyon

Arianna Huffington wants you to get more sleep.

Arianna Huffington wants you to leave your phone, with its blue light and sleep-disrupting screen, outside your bedroom and get some sleep.

In 2007 the co-founder of The Huffington Post collapsed from exhaustion. Blacking out was the wake up call that put in motion Huffington’s transformation from sleep deprived to sleep enthusiast. In a 2010 TedWomen talk Huffington suggested that the secret to a “more productive, more inspired, more joyful life” was sleep. And the data agrees with her: in the US alone the total annual cost in productivity caused by sleep deprivation is $63 billion.

Humans spend a third of their life asleep, so it’s not surprising that sleep deprivation’s effects aren’t limited to decreasing the productivity of the US economy. As Huffington points out in her newest book, The Sleep Revolution, the amount of sleep we get influences everything from our ability to pay attention to our caloric intake and the situation is no different when it comes to learning and memory.

A good night’s sleep both prepares our brain to receive new information and also allows our brains to more efficiently remember this information. Being told to “sleep on it” may be an idiom as old as time itself, but the science behind why “sleeping on it” improves our memory is relatively new and continues to be heavily explored.

Sleepless in Sweden

A 2015 study with over 20,000 Swedish adolescents (12 to 19 years old) showed an association between academic failure and self-reports of both sleep disturbances and short sleep duration. While the study did not focus on whether sleep deprivation was the cause of academic failure or vice-versa, the researchers did find that Swedish adolescents who slept less than seven hours were significantly more likely to fail at least one school subjects than their peers getting 7-8 hours of sleep. Research groups from across the globe have come to similar conclusions when looking at the effect of sleep disturbances on GPA (grade point average) and cognitive function (memory, attention and math fluency).

Despite multiple research papers pointing towards the importance of sleep for educational success, teenagers and young adults simply aren’t getting enough sleep. After convening a panel of experts and systematically reviewing the latest research, the National Sleep Foundation released a new set of sleep recommendations in 2015: teenagers (14-17 years) should get eight to ten hours of sleep while college-aged young adults (18 to 25 years) need seven to nine hours of sleep (Figure 1). In truth only around 15% of teenagers get 8 and half hours of sleep during weekdays and 70.6% of college students get less than 8 hours of sleep per night.

Image 1 (Sleep Recommendations): Sleep recommendations from the National Sleep Foundation for school children, teenagers and young adults. Adapted from National Sleep Foundation
Figure 1: Sleep recommendations from the National Sleep Foundation for school children, teenagers and young adults. Adapted from National Sleep Foundation.

For the sleepless college and high-school student it may seem contradictory that the time spent sleeping and not studying might be just as effective as the time spent re-reading class notes for boosting academic performance. For centuries sleep was seen as a sort of “time-out” for the brain, but in reality while we rest our brains are hard at work taking all the experiences we had during the day and transforming them into memories.

To sleep, perchance to dream, perchance to… strengthen neuronal networks?

Memories have three main stages: encoding, consolidation and retrieval. Encoding involves the acquisition of a new memory, such as the directions for how to get to work or the lines of Hamlet’s soliloquy from William Shakespeare’s play Hamlet.

These newly encoded memories are fragile things, prone to decay. For instance, say you just learned that the beginning of Hamlet’s soliloquy is “To be, or not to be – that is the question”. At first your memory of this opening line is shaky, but after going through a process called consolidation, your ability to remember Shakespeare’s eternal words is strengthened.

The final main stage is retrieval, which is when we recall a piece of information after an appropriate stimulus. For the high school or college student facing finals, the stimulus would be a question on their English exam about Hamlet’s soliloquy. If the student has both studied and slept enough, their memory provides the answer.

In writing, the progression from encoding to consolidation to retrieval seems straightforward, but in the actual brain, memory formation is a bit more intricate and has been the subject of intense study for over 40 years.

The cells in our brains, neurons, are connected into networks by synapses, which allow the passage of electrical or chemical signals from one neuron to another. When a new memory is encoded, a network of neurons is activated, resulting in a strengthening of the synapses between the activated neurons. This strengthened network is the neuronal representation of a memory.

Sleep’s role in memory formation comes during consolidation, which occurs in part during sleep. While the exact science behind consolidation has not been entirely parsed out, the prevailing hypothesis is that during sleep the neurons in the network become reactivated causing our brains to actively replay the networks into which new memories have been encoded. This activity strengthens the synaptic connections between the neurons in the network and this in turn transforms labile memories into something that can be retrieved (Figure 2). Multiple studies, for instance, have shown that our ability to recall word-pair associations increases when we sleep between learning and testing.

Figure 2: Memory formation involves three stages: encoding, consolidation and retrieval. When we learn something new it becomes encoded into a neuronal network, which is formed by a group of neurons connected by their synapses. When we sleep, the memory consolidates, synapses are strengthened and the neuronal network becomes dormant. The final stage occurs after a certain stimulus re-activates the neuronal network, transitioning it from dormant to active and allowing the memory stored in that network to be retrieved. Adapted from Finding the Engram.
Figure 2: Memory formation involves three stages: encoding, consolidation and retrieval. When we learn something new it becomes encoded into a neuronal network, which is formed by a group of neurons connected by their synapses. When we sleep, the memory consolidates, synapses are strengthened and the neuronal network becomes dormant. The final stage occurs after a certain stimulus re-activates the neuronal network, transitioning it from dormant to active and allowing the memory stored in that network to be retrieved. Adapted from Finding the Engram.

Once a memory becomes consolidated after a good night’s sleep, the memory becomes dormant, waiting for just right kind of stimulus to become active again. But, memories aren’t forever. Once a neuronal network becomes reactivated it becomes unstable again and can have one of two outcomes: it may be re-consolidated or it may decay and be lost. We have all experienced this rapid memory decay after dumping a semester’s worth of knowledge into a final exam. We forget Hamlet’s full soliloquy and remember only that opening line: “to be, or not to be – that is the question”.

To sleep or not to sleep – that is no longer a question

As neuroscientists continue to explore the mysteries of sleep’s importance to memory formation, a growing body of stats serves as a warning to how harmful sleep deprivation can be. For instance, drowsy drivers cause 328,000 car accidents yearly in the US and lack of sleep has been correlated with increased incidences of heart attacks, strokes, diabetes and obesity.

When sleep’s current cheerleader Arianna Huffington released her book The Sleep Revolution, she also launched the Sleep Revolution College Tour with the intent of giving “students tangible tools and products to learn better sleep habits and make small but transformational changes in their lives.” Participants in the college tour could attend panels with sleep experts and receive sleep-inspiring products such as pajamas and slippers.

But eye masks and candles and personal awareness can only bring incremental changes to the global issue of sleep-deprived students. To really fix the problem institutional changes, such as lowering the workload or starting the school day later, need to be implemented so that pulling an all-nighter is no longer necessary. Nauset Regional High School on the Cape in Massachusetts did just that, pushing the school’s starting time from 7:25 to 8:35 back in 2012. The verdict? Grades went up and tardiness went down. Despite the occasional success story, the fight for more and better sleep continues and now, with both researchers and media moguls championing it, sleep may finally take its place in preventive healthcare alongside nutrition and exercise.

Fernanda Ferreira is a PhD student in the Virology Program at the Harvard University.

Further Reading

Arianna Huffington’s The Sleep Revolution

James Vaznis’ Boston Globe article Students find more awareness with later starts

National Sleep Foundation’s new sleep recommendations

Trends in Neuroscience opinion article on system consolidation during sleep (Open Access)

Top Image: Henri Rousseau’s Sleeping Gypsy (1897) Henri Rousseau via Wikimedia Commons

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