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my other persona goes to school
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. Historically, Sleep has popularly been thought to simply provide energy conservation, but when test subjects are deprived of sleep and then monitored by an EEG, slow wave sleep (or NREM, the most restful phase of sleep), increases only slightly (Martin 243). In fact, the amount of energy saved after 8 hours of sleep is only about 50 kilocalories--you could get the same amount by eating a piece of toast (BBC 2006). Theories on why we sleep are in no short supply, but for the sake of brevity, I will stick to a few of the more accepted theories.
The Repair Theory
The repair theory suggests that sleep--particularly NREM sleep-- is used as a time for physical growth and recuperation. Seemingly in support of this, it is known that a large amount of growth hormone is released at the onset of sleep (providing half the total amount of growth hormone released in a 24 hour cycle). However, recent studies have shown that if a person is deprived of sleep, larger pulses (releases) of growth hormone will be released throughout the day to supplement for what would have been released in a single larger pulse had the individual slept (Brandenburger, Gronfier, Chapotot, Simon, & Piquard). So sleep deprivation does not affect the amount of growth hormone received, it just changes how much growth hormone is received per pulse.
The repair theory is not without valid argument, though. The production of protein and nucleic acids increases during NREM sleep (Martin 243) . Noting that protein is necessary for the maintenance of all living cells, and nucleic acids are the “building blocks of DNA”, this process directly supports the repair theory. Also during NREM, “there is a decrease of catabolic hormones and an increase in anabolic hormones in the body. The catabolic hormones tend to wear the body out, while the anabolic hormones tend to build up and restore the body.” (Moorecroft 422) Thus sleep can be thought of as restorative.
REM Sleep and memory organization
Another theory is that the brain uses REM sleep as a time to organize memory. Pieces of information--people, events, emotions-- get shuffled and sorted through and extraneous bits are disposed of as a sort of 'brain maintenance', according to celebrated British scientists Francis Crick and Graeme Mitchison, who proposed the theory in the early 1980's. They called this trimming of information "reverse-learning", and state that dreams are simply the byproduct of this (Martin 247).
Somewhat similar to the reverse-learning theory in regards to the sleep-memory connection is the theory of dynamic stabilization. This theory surmises that "information, both inherited or learned, is remembered by repetitive use of the circuits which store the information", and that dreaming is the result of replayed fragments of memories and information rearranging itself (Miller 3). As opposed to the reverse-learning theory, the theory of dynamic stabilization deals with the consolidation of memory, not the deletion.
Undoubtedly, information and experiences gained from the previous (waking) day play a role in REM sleep. Otherwise, why would dreams so often hold relevance to the day's events? For example, my boyfriend will often report to me his dreams about war and combat. I can easily draw a line from the war game he spent two hours on just before bedtime, and the particular violence of his dream. I can also speculate that my dream contained my turtle, Chauncey, because I was thinking about cleaning his cage and buying a new light for him and was feeling a bit guilty that I didn't actually do anything about it just prior to bedtime. My personal conjecture won‘t persuade the scientific community, but recent studies on REM sleep and learning provide some interesting data and more insight.
Sleep Experiments
Considering the magnitude of the subject, I found many thought provoking examples of ongoing sleep research being done around the world. Following are a few of the most relevant experiments I came across.
Learned Processes and Sleep
Researchers at the Massachusetts Institute of Technology implanted tiny electrodes into a number of rats' brains, rats which they had earlier trained to run through a particular maze. They monitored the brain activity of the rats while they ran through the maze, and again while they slept. The researchers found that when the rats ran the maze, the neurons in the hippocampus (an area of the brain related to declarative memory) fired in a specific pattern, which differed from neuronal patterns that had been recorded when the rats ran a new maze, or ran the same maze with different treats, etc. The researchers found that during REM sleep, the neurons would fire in the same pattern as that which the rats exhibited while running the learned maze. It was so exact, in fact, that "the scientists could pinpoint where on the maze the rats were dreaming they were, and how fast they were running in their dreams." ("Dreaming of the rat race")
Yet another experiment, led by a research team at Harvard, used human subjects in an attempt to link learning and memory to sleep. Participants were to press particular buttons in response to symbols shown to them on a computer screen. While performing the newly learned task, participants‘ brain activity was recorded. Subsequently, while they slept, participants were subject to brain scans. An analysis of the brain scans showed that areas of the brain that were active while performing the task matched areas of the brain active while participants experienced REM sleep. Control subjects who had not learned the task did not exhibit similar patterns (Martin 252). From this result, it would be easy to deduce that REM sleep plays a definite role in the ability to process and retain procedural memory, or, in short, learning.
Memory Formation and Creativity
Another experiment, led by researchers at the University Of Chicago, used Zebra finches (Martin 252). The researchers recorded the neuron firing patterns in the finches' brains while they sang--as zebra finches are song birds that rely heavily on their call for mating and survival--and then played the recording of their song back to the birds as they slept. They found that the sleeping bird seemed to hear the recording while asleep, and the same neuron firing pattern ensued in the finches brains. When the researchers monitored the sleeping finch without interference, the neuron firing pattern was still similar to the original waking song pattern they had previously recorded, with slight variations. The research team hypothesized that the finches were practicing new variations of their song ("Learn to Sing, While You Sleep"). This lends credence to the idea that sleeping is a time for memory formation and creativity.
In fact, many great thinkers claim that a groundbreaking idea came to them in their sleep. For example, Albert Einstein claimed that a dream of his helped him come up with the theory of relativity. Friedrich Kekule, nineteenth century German chemist, attests that the molecular structure of benzene came to him in a dream--an issue he’d been struggling with for years. Descartes wrote that a dream inspired his entire philosophic system. Guiseppe Tartini, an Italian violinist and composer, says that he dreamt his sonata “The Devil’s Trill”. Mary Shelley avowed that the idea for Frankenstein came to her in a dream. ( Martin 200-203) The list goes on.
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