Memory, Sleep, and the Modern Student

Throughout every experience we have, there are thousands if intricate signals traveling throughout the body, especially in the brain. Every second we are unconsciously taking in information, much of which we disregard, but some of which we are able to recall at future times – this is what we know as memory. Understanding memory consolidation is a problematic thing: because of the mysterious intricacies of the brain, creating definitive experiments is very difficult, as it usually is with science. Trying to understand this role of sleep in memory consolidation is important to all of us, especially the modern student.

There are two types of sleep that both people and animals go though: REM and NREM sleep. REM (Rapid Eye Movement) sleep is the deeper of the two states, often associated with dreaming, and is characterized by a rapid eye movement, decrease in muscle tone, and low-amplitude, fast EEG oscillations. This phase lasts around 1.5 to 2 hours in an average adult human and occurs in the late part of the sleep cycle. NREM (non-Rapid Eye Movement) sleep, the other sleep phase, is characterized by large-amplitude, low frequency EEG oscillations. This phase is divided into four stages, the deepest of which is the SWS (Slow Wave Sleep) stage. The four NREM stages account for the rest of the sleep duration (1, 2).

Memory consolidation is the process by which conscious thoughts are turned from short-term to long-term memories. This involves strengthening of synapses between neurons in the brain. For a long time it was thought that memory consolidation was determined simply by length of time, however this theory has been mostly disproved (4). According to Duke University researchers, now it is believed that memory consolidation is largely tied to the sleep process: NREM sleep in processing memories and REM sleep in the actual consolidation process (3). This means that while we are sleeping. The NREM part of the sleep cycle is resting our bodies, lowering stress factors and relaxing us and processing some of the inputs we experiences in the last awake period, while the REM cycle is actually working more to strengthen the synapses in the brain, consolidating these connections into memories as deemed fit by the brain. As opposed to earlier hypotheses which stated that only the hypothalamus and the cerebral cortex were involved in this process, researchers noticed signal reverberations in a wide area of the brain, showing many parts working together in all processes of memory consolidation. Also, their research showed that the length of time that these observed areas of the forebrain demonstrated considerable activity is significantly longer than previously examined. Furthers studies done by researchers at Beth Israel Deaconess Medical Center use functional magnetic resonance imaging (fMRI) to look at these said active areas of the brain during sleep observation. What they found was similar to that of the Duke researchers: certain parts of the brain are more active than others during the course of sleep, but overall a full night’s rest activates many different segments of the forebrain and instigates improvements in memory retention and motor skill performance of tasks learned before the sleep period.

Research on these topics has become very popular in recent years. A well-known review of the commonly used approaches to sleep, memory, and dreams, “The REM Sleep-Memory Consolidation Hypothesis,” offers criticism on some of these techniques (5). Author Jerome Siegel points out that there are many difficulties in experimenting in this area due to the complexity of the brain. As we have learned, there is not simply one input for every output, and likewise the processes of the brain surrounding memory consolidation involve more than the memory coming in and the consolidation process going through. Factors such as stress can cause chemical changes in the brain, disrupting sleep and altering tests unbeknownst researchers. There are also issues with dependency, especially with animal tests subjects. For example, if a drug is disrupts REM sleep in a test subject and that subject is then woken up, un-drugged, and seems to show little memory consolidation, there is the possibility then when, back in a drugged state, the memory could be accessed again. Many of the tests done today involve deprivation techniques, meaning they are deprived of proper sleep patterns in order to study the adverse affects. I find it interesting that these methods are relied upon so heavily – it seems that if only these approach is taken that whole other possibilities and outcomes may been missed.

These studies are particularly important to the modern student. As higher education continues to intensify, more and more students are falling prey to what researcher Matthew Walker describes as “sleep bulimia,” meaning students deprive themselves of sleep during the week due only to later over-sleep on weekends to try and make up for their loss (4). Walker and his fellow researchers have concluded that sleep is essential not only for memory consolidation in everyday thoughts and events, but for over all human development. Approximately 70% of an infant’s sleep time is taken up by the REM stage, whereas only 1.5 to 2 hours of the average adult’s sleep is spent in the REM cycle. Infants are in a constant learning process for the first few years of their lives, and this increase in duration of the REM phase is related to that need, according to Walker. For the student, this means that staying up late to study, or likewise not sleeping at all, most likely has averse effects on the amount of information retained (7). There is a window of time that allows for a person to be awake (about 40 hours) where they can retain information without sleeping. After this window is gone, it is much more difficult to maintain information in the same way. A full sleep cycle is needed to, in a way, anchor the information learned in the previous information window down into a permanent memory state. As mentioned earlier, stress can have adverse affects on the REM cycle, meaning that even if a student were to get the fully recommended amount of sleep, the stress that naturally accompanies the academic process could undermine these efforts further. It seems, in this respect, that the way academic institutions are set up is completely non-conducive to collecting the most amount of information possible.

Whichever way you choose to look at it, the study of sleep is a very tricky one. The brain is an intricate machine, one that is impossible for us to fully understand. Every action, thought, and human process that goes on within each person is a product of huge amounts of inputs, outputs, and interactions in between. In forming memories, it seems that sleep is key in consolidation, however because of the natural intricacy of the human brain the quest for definitive answers is always elusive.

WWW Sources
1) http://en.wikipedia.org/wiki/Sleep; “Sleep,” Wikipedia.
2) http://www.learnmem.org/cgi/content/full/11/6/671; “Sleep, Dreams, and Memory Consolidation: The Role of the Stress Hormone Cortisol,” Learning and Memory.
3) http://www.sciencedaily.com/releases/2004/01/040119081420.htm; “Evidence That Memories Are Consolidated During Sleep,” Science Daily.
4) http://www.sciencedaily.com/relases/2005/06/050629070337.htm; “Study Shows How Sleep Improves Memory,” Science Daily.
5) www.sciencemag.org/cgi/reprint/294/5544/1058.pdf; “The REM Sleep-Memory Consolidation Hypothesis,” Science AAAS.
6) http://www.abc.net.au/cgi- bin/common/printfriendly.pl?/science/news/stories/s216359.htm; “Sleep Improves Memory,” News in Science.
7) http://www.sciencedaily.com/releases/2000/11/001122075125.htm; “New Reason to ‘Sleep On It’,” Science Daily.