Sleep Physiology and Chronobiology: Understanding Sleep Function
a. Global vs Local Aspects of Sleep
Sleep occurs locally but demonstrated globally
We live our entire life in two states, sleep and awake1. These two states are characterized by two distinct behaviors. For instance, the brain demonstrates a well-defined activity during non-REM sleep (nREM) that is different when we are awake. In the study of sleep by Huber et. al., the authors stated that sleep is in fact a global state2. It is unclear whether this statement means that sleep is a state of global behavioural inactivity or the state of the global nervous system. The notion that sleep is a global state of the nervous system served as basis for sleep researchers to search for a sleep switch. The discovery of the sleep switch, in return, provided evidence and enhanced the notion that sleep is a global state of the nervous system. The switch hypothesis developed from the fact that sleep can be initiated without fatigue and it is reversible1. It was hypothesized that there is something in the brain that has the ability to control the whole brain and initiate sleep. Studies have found a good candidate that demonstrated this ability3. They found a group of neurons in the Ventrolateral Preoptic (VLPO) nucleus. It was a good candidate because it was active during sleep, has neuronal output that can influence the wakefulness pathway, and lesion in the area followed reduce sleep3. The idea that there is something that can control the whole brain and result sleep state supports the idea that sleep is a global state of the nervous system.
Recently, however, intracortical recordings of epileptic patients and of mouse brain during sleep found evidence that the brain can have region...
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...ep. There are events in sleep that are associated with synaptic modification, which is the basis of brain rewiring that enhances cognition. There is evidence that sleep accelerated transcription of cortical genes that are associated with protein synthesis9. These newly generated proteins are known to be required for strengthening of existing synapses and building new synapses. Studies have found increase of factors associated with brain-plasticity and enhanced learning during sleep5. These factors include phosphorylated or activated CREB, a transcriptional factor, as well as Arc, BDNF, and NGFI-A. These evidence help explain how sleep can influence brain rewiring through synaptic modification. This mechanism helps explain how sleep can modify the brain and ultimately enhance learning. This is a strong evidence that supports the synaptic downscaling hypothesis.
All mammals exhibit Rapid-Eye-Movement, or REM, sleep, and yet on certain levels this type of sleep would seem to be disadvantageous. During REM sleep, which is when most dreams occur, the brain uses much more energy than during non-REM (NREM) sleep. (1) This "waste" of energy coupled with the increased vulnerability of this state on account of the body's paralysis at this time suggests that there must be a very important reason, or reasons, for the existence of REM sleep and in extension of dreams. Determining the function of dreams, however, has proved very problematic with many arguments which directly oppose each other. Some of the primary functions of dreaming have been tied to is role in development, its production of neuro-proteins, and also to how it may allow for the "rehearsal" of neurons and neuronal pathways. The influence of dreaming on learning is one of the hottest debates. Some argue that dreams aid in learning, others that dreams aid in forgetting, and yet others that dreams have no effect on learning or memory. That REM sleep seems to aid in development might argue that REM sleep may be connected to learning. It seems that most scientists believe that REM sleep aids in certain memory consolidations although some argue that it actually leads to "reverse learning.
Sleep deprivation is a commonplace occurrence in modern culture. Every day there seems to be twice as much work and half as much time to complete it in. This results in either extended periods of wakefulness or a decrease in sleep over an extended period of time. While some people may like to believe that they can train their bodies to not require as much sleep as they once did this belief is false (1). Sleep is needed to regenerate certain parts of the body, especially the brain, so that it may continue to function optimally. After periods of extended wakefulness or reduced sleep neurons may begin to malfunction, visibly effecting a person's behavior. Some organs, such as muscles, are able to regenerate even when a person is not sleeping so long as they are resting. This could involve lying awake but relaxed within a quite environment. Even though cognitive functions might not seem necessary in this scenario the brain, especially the cerebral cortex, is not able to rest but rather remains semi-alert in a state of "quiet readiness" (2). Certain stages of sleep are needed for the regeneration of neurons within the cerebral cortex while other stages of sleep seem to be used for forming new memories and generating new synaptic connections. The effects of sleep deprivation on behavior have been tested with relation to the presence of activity in different sections of the cerebral cortex.
Rasch, B., & Born, J. (2008). Reactivation and consolidation of memory during sleep. Current Directions in Psychological Science, 17, 188-192. doi: 10.1111/j.14678721.2008.00572.x
As we all know, sleep is an important part of our lives. Without the proper amounts and type of sleep, fatigue and other problems can arise. Generally, we can clearly distinguish between a sleeping person and a person that is awake. With sleeping disorders, the distinction between an awake person and a sleeping person becomes more intriguing. What is the difference, how does it relate to the I-function and consciousness? Each sleeping disorder has its own unique answer to this question. It is essential to understand sleep to fully appreciate it. However, many aspects of it remain a mystery. We do have some degree of understanding of sleep. Within our sleep cycle a type of unusual sleep occurs, REM sleep. During this cycle the periods of REM sleep are interspersed with slow wave sleep in alternation. Each period of REM sleep (there are usually 4 or 5 periods a night) lasts for approximately 5 to 30 minutes. During these periods a sleep paradox occurs. An enormous amount of brain activity takes place; this is sometimes even more activity then when awake. This clearly indicates that sleep is not simply to rest our mind and not to think. So, during this period our brains are extremely active, yet there is usually no input or output. During this period, along with the random eye movement (REM), there is a complete loss of muscle tone. Essentially, at this point, the motor system is paralyzed (normally the body inhibits any movement). The autonomic nervous system also alters its behavior. The regulation of body temperature is lost and the blood pressure, heart rate, respiratory rates shows increased variability. REM sleep can be detected by measuring the electrical activity of the brain with an electroencephalogram. At this point, the EEG will show the same pattern of activity as when the brain is awake.
In a short story called," Sleep," written by Haruki Murakami and translated by Jay Rubin, is a story about from the perspective of a thirty years old woman who is a respected housewife in the day time and a woman who does things which aren 't routine in her night life. This short story holds many controversial viewpoints of a person 's perspective as they read through to better understand what the main character is going through. The main character goes through a transformation as she suffers from insomnia and tries to understand what the true version of herself is.
Sleep is defined as a reversible, natural state of reduced responsiveness to external stimuli and relative inactivity, accompanied by a loss of consciousness1. This state of inactivity has been evolutionary conserved across species against many selection pressures. This suggests that sleep holds a vital function. Multiple studies have suggested that sleep enhances both declarative and procedural memory 2,3. Consequently, memory consolidation is one of the ostensible functions of sleep. The active system consolidation hypothesis and the synaptic homeostasis hypothesis (SHY) are the two main hypotheses for this putative function of sleep. The active system consolidation model proposes that the repeated reactivation of newly encoded representations in the hippocampus during slow wave sleep (SWS) drives a transfer of memory traces from short-term store in the hippocampus to neocortical regions for long term storage4. These representations are stabilized in the neocortex during subsequent periods of REM sleep by synaptic potentiation5. SHY proposes that sleep acts to homeostatically renormalize synaptic weight to counteract the potentiation that occurs during wake6,7. This occurs by an activity dependent downscaling of synaptic weight during SWS. These models are often portrayed in direct opposition, largely due to the active potentiation proposed in the active system consolidation model, in contrast to the global downscaling (depotentiation) of SHY. However it has recently been considered that these two models may not be mutually exclusive, but could act in unison8. This essay will analyse what I believe to be the best evidence in support and against each model to contend the role of sleep in memory consolidation. The rol...
The most popular natural aid for sleep is melatonin. Supplementation with melatonin has been shown in several studies to be very effective in helping to induce and maintain sleep in both children and adults, and in both people with natural sleep habits and those with insomnia. However, the sleep-promoting effects are most apparent if melatonin levels are low. In other words, using melatonin is not like taking a sleeping pill. It has a sedative effect only when melatonin levels are low. When melatonin is taken just before going to bed in normal subjects or in patients with insomnia who have normal melatonin levels it has no sedative effect. This is because there is normally a rise in melatonin secretion just before going to bed. Melatonin supplementation appears to be most effective in treating insomnia in the elderly, in whom low melatonin levels are quite common.
Mignot, Emmanuel, Shahrad Taheri, and Seiji Nishino. "Sleeping with the Hypothalamus: Emerging Therapeutic Targets for Sleep Disorders." Nature.com. Nature Publishing Group, n.d. Web. 15 Dec. 2014.
Sleeping is something that is an essential part of human nature and is a must in order for one to be a functional human being. Sleep is an idea that is accompanied by many wives’ tales, including the idea that one needs seven to eight hours of sleep each night and alcohol helps one fall asleep and sleep more soundly. One myth about sleep is that during sleep, one is in a state of nothingness. In truth, however, it has been discovered that during sleep the brain is active, variations in heartbeat and breathing occur, and the eyes and ears are active throughout the time of sleep. These activities during a person’s sleep are important because they help that person be more aware, awake, and alert during sleep.
Doctors have been saying for years that you should not stay up late, or not to sleep in during the day. Doing these things can lead to dementia, heart disease, and early death. One part of sleep is actually found to be more important.
Kales, A. (1972). The evaluation and treatment of sleep disorders : Pharmacological and psychological studies. In M. Chase (ed.)The Sleeping Brain. Los Angeles : Brain Information Service.
Alzheimer’s disease affects the brain’s intellectual functions due to the memory deteriorating and is the common cause of dementia. Sleep regulation is disrupted and sleep is in fragments during the night with a reduced period of deep REM sleep (Epstein,
Sleep is very important to our body for relaxation, preparing ourselves for the next day. Unfortunately, poor sleeping quality is prevalent in modern cities such as Hong Kong. An increasing number of university students have stated sleep problems. (Suen, Hon & Tam, 2008). Meerlo, Mistlberger, Jacobs, Heller & McGinty (2009) have reported that prolonged sleep loss may affect the rate of neurogenesis...
Rasch, Björn, and Jan Born. "About Sleep 's Role in Memory." Physiological Reviews. American Physiological Society, n.d. Web. 06 May 2016.
Sleep is a very important factor in the human function. Our body and brain is able to reset itself and rejuvenate while we sleep. When we do not get the required amount of sleep, we start to feel lethargic and foggy minded, because our mind and body wasn’t able to replenish itself. Sleep is imperative that an insignificant rest deficiency or lack of sleep can affect our ability to remember things; decisions and can affect our temperament. Chronic sleep deficiency can get the body to feel agitated and it could lead to serious health problems such as, heart problems, stress, acne, and obesity.