The Effect of Sleep on Memory

The Effect of Sleep on Memory Human tend to forget things. Hermann Ebbinghaus is one of the psychologist to study the topic of forgetting. Forget is a gift to the human because if human remember every single event and phenomena that occurs in the daily life, they will suffer a lot. They will remember the feeling of pain and sadness of losing someone who is important to them forever. Forgetting does not mean that the information stored in the long term memory is being deleted or removed. Instead, forgetting means a failure in memory retrieval (Cherry, 2014). This can be seen commonly among the students when they are sitting the examination. Tip-of-the-tongue explains this situation well. Tip-of-the-tongue is a feeling that a person knows something, but the person cannot retrieve it (Margaret Matlin, 2005). Memories are stored in a brain region called hippocampus (Miller, 2010). Lack of sleep will affect the proper function of hippocampus. (Contie Wein, 2013). Memories are formed when the nerve cells in the brain are reinforced. Memory also includes the three stages which are encoding, storage and retrieval. The encoding stage is the process of convert the information received into a usable form. After the information is being encoded, the information will be stored in the brain for future use. However, the stored memory stays outside the conscious awareness. When a person wants to use the information and try to retrieve it from the stored memory, this process will occur under conscious awareness (Cherry, 2014). There are different stages of sleep which include rapid eye movement sleep (REM) sleep, non-rapid eye movement sleep (nREM) which consists of stage one sleep, stage two sleep, stage three sleep and stage four sleep. When a person sleeps, they will start off with nREM sleep follow by REM sleep. Hence, during the sleep process, the body will encounter a cycle of REM sleep and nREM sleep (WebMD, 2014). During nREM sleep, the body will utilize this time to reproduce and rebuild tissues, bones and muscles. Besides that, immune system in the body is also enhanced during this time. Stage one and two in nREM sleep are also called as light sleep while stage three and four are also called as deep sleep (WebMD, 2014). Dreams occur during the REM sleep. This is due to the high activities that occur during the REM sleep and the brain wave patterns observed during REM sleep is similar to the brain wave patterns observed during wakefulness. REM sleep is described as rapid eye movement sleep because during this stage of sleep, human’s eyes move rapidly to different directions. REM sleep is described as a stage of sleep that composed of the combination of brain excitement and muscle immobility. However, REM sleep only accounts for a short period of time in the sleeping process which accounts for twenty percent in sleeping among adults and fifty percent among infants (WebMD, 2014). Sleep plays an essential role in memory, both before and after learning a new task. Besides that, sleep also affects a person’s mood, emotion, motivation and judgment. Sufficient of sleeping hours can help a person to focus attention and thus receive information in a more efficient way. After people sleep, the sleeping process helps to reinforce what people learn during the day. (Harvard Medical School, 2007). This is because study shows that when a person is using the right brain to do task during his or her wakefulness, the slow waves at right brain become larger show that the right brain are exhausted by the task being performed. Interestingly, the brain also will shut down parts of its neurons. This phenomenon is known as local sleep. Besides that, sleep also helps one to link the new memories with the old ones. When people sleep, the brain will review the memories and decide which memory needs to be strengthened. If people do not sleep, their ability to learn new things will drop by up to forty percent ( Contie Wein, 2013). However, different stages of sleep help in different type of memories. Rapid eye movement sleep (REM) plays a critical role in emotional memory (Contie, 2013). Research also shows that after REM sleep, a person can recognize the emotional picture better compared to the neutral ones. Hence, REM sleep helps in reinforcing the emotional content in the memory ( Born, Diekelmann, Groch Willhelm, 2013). Hence, when one spends more time in REM sleep, one can overcome the painful memories in their life. This is because during the REM sleep, the stress chemistry will be suppressed such as the norepinephrine. Then, the brain will process the emotional memories and remove the difficult and painful memories. Experiment shows that when the participants having a full night of sleep after view emotional images, the magnetic resonance image (MRI) shows that there is a great reduction of reactivity in amygdala. Amygdala is a region in the brain that involves in anger and fear. Hence, this allows the forebrain to have a control in a person’s emotions (Walker, 2011 as cited in Anwar, 2011). Furthermore, a physician at a United States Department of Veteran Affairs hospital in the Seattle also discover that by prescribing drugs that can decrease the blood pressure of patients can help in preventing the occurrence of nightmares in Posttraumatic Stress Disorder patients. This is because drugs that can decrease the blood pressure of patients will suppress the level of neurotransmitter norepinephrine in the brain. Therefore, by possessing sufficient amount of REM sleep, PTSD patients can decrease the occurrence of nightmares during the night and have a greater quality of sleep because there is a decrease level of neurotransmitter norepinephrine (Anwar, 2011). Furthermore, research also shows that sleep deprivation can cause psychiatric disorder such as depression and anxiety disorders. Experiments that are carried in this research also show that when normal people are deprived of sleep, the brain wave patterns will look like the pathological psychiatric patterns. Functional magnetic resonance image ( fMRI ) also shows that  participants who do not experience a night of sleep are having a greater reactivity compared to those participants who experience a night of sleep. Hence, this also means that amygdala is active when a person is lack of sleep. This will cause those participants who are lack of sleep to show higher emotion intensity (Walker, 2007 as cited in Anwar, 2007). This is because high activity in amygdala is observed when a person is lack of sleep. This will cause the amygdala to lose connection with the front brain. The connection plays an important role because the front brain is responsible for rational reasoning and releases neurochemicals that can calm down a person when a person is in a nervous state. Instead, when a person is lack of sleep, amygdala will connect to the brain region of local coeruleus instead, which will cause the release of noradrenaline (Walker, 2007 as cited in Anwar, 2007). Furthermore, there is also experiment that has been carried out to see the effect of variables: sleep and memory on mental disorder. Result shows that major depression patients who have divorced experience deteriorated depression when they do not dream about their ex-spouse. Since lack of sleep has a bad effect on mental disorder, intervention such as promotion of good sleep can treat mental disorder such as depression, anxiety disorder and PTSD. This is because sleep helps in consolidating the memory. Therefore, therapist can utilize this finding in the psychotherapy. Therapist can promote and encourage patients to sleep after receive treatment or psychotherapy. This is because during the sleeping process, patients can reinforce and integrate the therapy content. Thus, this can help the patients to rebuild healthy thoughts in themselves. Besides that, slow wave sleep also plays an important role in reinforcing the episodic memory that is stored in the hippocampus and transform them into long term memories ( Born Inostroza, 2013). Episodic memory is a long term memory about specific events, situations and experiences (Cherry, 2014). Furthermore, when people are getting sufficient of sleep, it also helps in the strengthening of motor memory. Different brain scans magnetoencephalography (MEG) and polysomnography (PSG) are being used in the research to trace the brain activity in the brain. Changes in fast sigma and delta brain waves are observed in the motor area of the brain explain the improvement in motor skills after a period of sleep. Participants who have slept after learning a motor task have a higher accuracy in performing the motor tasks. Motor learning can be strengthened during the sleeping process because more brain energy is available ( Tamaki, 2013 as cited in Grohol Wood, 2013). Moreover, sleep also helps in converting short term memory into long term memory. Experiment is carried out by using genetically modified fruit flies. In the experiment, scientists modify some male fruit flies to smell like female fruit flies. After that, scientists expose the male fruit flies to the â€Å" fake† female fruit flies. After a few times of unsuccessful tryout to approach the ‘fake’ female fruit flies, male fruit flies know the fact that those ‘fake’ female fruit flies are not female fruit flies. After that, the experimenter makes some fruit flies to sleep. Results show that after the fruit flies sleep, they able to retain the information about the ‘fake’ fruit flies for several days compared to those fruit flies have not slept. Fruit flies have not slept only can retain the information for a few hours (Breus, 2011). Besides that, research also shows that REM sleep plays a role in enhancing creativity. The ability to think creatively relies on the process of schema disintegration. Schema disintegration is the highest level of memory change which involves the process of disintegration of existing schemas. This will allow ‘outside the box’ thinking. Experiment finds out that participants who have experience REM sleep can find words to produce meanings in three unrelated words such as dream, day and light. From the experiment as described above, scientists also find out that the process of information learning leads to the formation of synapses in the brain. Synapses communicate the information that has learned inside the brain. However, study also shows that during the sleeping process, the connection of nerve cells in our brain actually weakens. This phenomenon is known as the synaptic homeostasis (Cirelli Tononi, 2012). This is actually a shocking fact because all of the mean time people tend to think that during the sleeping process, the nerve cells in the brain are strengthened to reinforce the memory and the things that people have learned during the daytime. This is because formation and strengthening of synapses in the brain consumes energy. If synapses are being reinforced during the day and night time, the brain will run out of energy eventually. Inside the brain, spontaneous firing of neurons which means that unimportant connection of neurons will be weakened or removed to allow the connection between important memory remain intact. In other words, this means that the brain has the ability to differentiate between irrelevant information and significant information. Then, the brain will weaken the synapses that link irrelevant information and preserve the synapses that link significant information. By doing this way, the brain can save more energy and preserve it for the next section of learning after one awakes. This phenomenon also explains the reason that all the organisms need sleep.