It’s fall, which can only mean one thing: school is back in session!
Some 20 million Americans the student body of our nation’s higher education establishments. The college years, often seen in our society as a person’s first taste of freedom, fosters a culture of self-expression and experimentation. But mixed in between spring break trips and pub crawls, students will probably be forced to attend a class or two in order to keep their grades up so the can stick around long enough to go to that next big party.
However, it might not be the beers nor the buds that keep students from learning what they need to pass (or better yet thrive); instead it may be their penchant for late nights that does them in.
These days, the “all-nighter” has become as synonymous with college as frat parties. Whether, it’s staying up to cram for midterms or to finish up a term paper, students aren’t getting enough sleep. Science says adolescents aged 18-24 need about eight hours a sleep, but many don’t. One survey of students at the University of Cincinnati found that only 24 percent of them reported getting the minimum of seven to eight hours of sleep and 55 percent reported getting less than seven hours. Another survey found that 60 percent of college students said they had pulled at least one all-nighter. What’s more concerning is the student’s attitude towards sleep; one study found that most college students brag about how little sleep they can operate on.
We’ve known for a long time sleep deprivation is bad for your health in a variety of ways, but research over the last few decades has shown that it also may impede your brain from learning.
Sleep states, brain regions and memory types
Mammalian sleep consists of two main states, which cycle through the night. These are slow wave sleep (SWS) and rapid eye movement (REM). The former dominates sleep earlier in the night and tapers off, while the latter takes awhile to get going and is high in intensity at the end of the sleep cycle. Research has shown that inducing and amplifying either state in model organisms increases learning and memory and that blocking these states can be detrimental to learning and long term memory formation.
One current theory states that memory consolidation occurs during sleep and that during SWS and REM different types of memories are consolidated. SWS appears to be the state in which declarative memories are stored. These types of memories are facts that one can declare verbally, this would include things like knowing that Charles Darwin wrote On the Origin of Species or that the capital of Nevada is Carson City. On the other hand, REM appears to be important for consolidating procedural and implicit memories. A procedural memory is one that involves remembering how to do something, like how to write a lab report, while implicit memories are those that rely on past experience without conscious thought. Remembering how to perform a literature search so you can write up that term paper is an implicit memory.
At the cellular level, the neurons that compromise the mammalian hippocampus are believed to be instrumental in memory creation and consolidation. As such, much of the research on learning and memory in model organisms has been done on this region. The discovery of place cells in the hippocampus was a seminal moment in this field. These are cells that were found to be active every time a rodent was in the same spatial location in a particular maze. As a rodent learns to maneuver a particular maze, the order of firing of the place cells (seen here in this video) is always the same as the subject progresses through the maze. Interestingly, when these trained subjects sleep, their place cells continue to fire in the same order they did as the subject progressed through the maze. Disrupting this process, decreases the efficiency at which the subjects learn and traverse the maze over time.
During sleep, synapses in the hippocampus (the junction of two neurons) are strengthened and organized, particularly through a cellular process known as long term potentiation (LTP). This is thought to be vital in the conversion of short term memories to long term memories (i.e. committing information on a flash card to memory). LTP occurs when one neuron activates another one for an extended period of time (occasionally as long as days) and occurs frequently in the hippocampus during sleep, however, when sleep deprived LTP can be prevented or inhibited. A protein called mTOR is believed to induce and accelerate the translation of proteins involved in LTP during sleep. However, studies have found that mTOR activation is blocked during sleep deprivation.
Sorry you can’t learn through osmosis
There seems to be sufficient science to say that sleep is vital to memory but often the coverage of this topic has skewed reality. Take the survey that found 60 percent of students had done at least one all-nighter; it also reported that lack of sleep was associated with a lower GPA but it failed to correct for a variety of things including the student’s choice of major (ask someone with a science degree if that matters) and class schedule (ask any professor if student performance in their 8am class is as good as their afternoon class). Despite these flaws, the study received major headlines in places like the The Wall Street Journal as part of a feature on the best way to study.
Other headlines fail to point out that most of the sleep studies have not been done on humans been on model organisms, like primates and mice. It is very hard to translate brain research in rodents et al. to humans. But because it is ethically challenging to manipulate the human brain in extraordinary ways in order to study it, researchers don’t have much choice. A lot of the evidence about sleep states produced robust relationships in models, but have failed to show such strong connections when researched in humans. Furthermore, although there does seem to be a lot of similarity in the ways our hippocampus function at the cellular level, those shared cellular processes are still highly disputed as to their exact importance in learning and memory. For example, long term depression (LTD), a process in which a neuron receives an extended inhibitory signal, had long been thought of as the opposite of LTP and therefore detrimental to new memory formation. However, recent evidence suggests this is wrong and LTD might be as important as LTP in learning and memory. The take home message is we still aren’t really sure how the human brain learns and remembers things.
If all of this science on learning and sleep are correct, there is still a major problem with the preception of this relationship in the public and the media. At some point, the material actually needs to be studied to be able to form the memory. Nobody can skim Grey’s Anatomy (the seminal text on anatomy, not the ABC soap opera), get a good night’s sleep, wake up and perform successful open heart surgery. It does not work this way. Learning and memory takes hard work, but if you want that hard work to pay off, so you can recall those learned facts than you do need to get some sleep.
Nicholas Staropoli is the associate director of GLP and director of the Epigenetics Literacy Project. He has an M.A. in biology from DePaul University and a B.S. in biomedical sciences from Marist College. Follow him on twitter @NickfrmBoston.