Human Sleep and cognitive brain responses - Myassignmenthelp.Com

Question: Discuss about the Human Sleep and cognitive brain responses. Answer: Introduction Sleep quality can be described as a person satisfaction from the sleep experience which includes initiation of sleep, sleep maintenance, quantity of sleep and refreshment after waking up from sleep. Sleep quality is an important for the researchers and the clinicians due to the high incidence of insomnia and sleep disorders and also the clear relation of proper functioning of health (1). This study is divided in to two parts: the first part is based on literature review of the sleep quality study; the second part focusses on the comparative analysis of two research articles among and the comparative analysis includes biases, validity, reliability, limitations, and comment on sample size, application or implication of research, and culture, religion and gender. Literature review Source keyword used No. of literature returned no. of collected literature Elsevier impact of light on sleep 25 8 shift work and jet lag 30 6 anxiety and pain 35 7 effect on sleep due to chemical substances 44 5 Researchgate impact of light on sleep 30 3 shift work and jet lag 45 2 anxiety and pain 30 4 effect on sleep due to chemical substances 55 4 impact of light on sleep Light is one of the major disruptor of sleep. It affects the sleep of a person through delaying the sleep which makes it hard for an individual to sleep. The invention of light bulb in the late 19th century has made humans to receive more exposure to light during the nigh time in comparison to invention of light bulb before. Generalization Light affects the sleep quality of our body and makes it difficult for us to fall asleep both directly and indirectly. Light acts to disrupt the internal clock of the body which affects our preferred time to sleep. Light affects the internal clock present in our body through the various light sensitive cells. Specific discussion from literature Usage of the light emitting electronic devices that aid us to communicate, read, communicate, entertain has increased to a great extent. The usage of this devices before the bedtime greatly prolongs the time taken to fall asleep. This affects the circadian clock of the body and inhibits the release of the hormone, melatonin. This reduction in the amount of the hormone affects the timing of sleep to a large extent (2, 3, 4, 5, 6). Portable devices like mobile phones, computer monitors, reading devices have affected the melatonin secretion due to the blue light emission from the emission from such devices. Light in the range of short wavelength (446-483 nm) affects adversely the melatonin secretion in humans. Whereas the blue light not only affects the melatonin secretion but also the cognitive performance and melatonin secretion through the non-image performing photoreceptors (7,8,9, 10). The circadian timing system within the human body is deeply synchronized with the several biochem ical and physiological processes, which also includes the regular rhythm of sleep order. Thus, the main inference is that the timing of the sleep and the duration is directly linked with the circadian clock. It has been found that the exposure to light at the evening and the early part of night, suppresses the release of the hormone melatonin even at low intensities. Due to this exposure, the circadian clock shifts to a later time which results in difficulty to fall asleep at night (11,12). Shift work and jet lag It is a normal phenomenon that our biological internal clock serves to work according to the time zone to which a person resides. However, problems occur when body gets exposure to light which changes depending to the sudden change in shift work or drastic change in time zone due to travel across different time zones. Generalization Individuals that frequent travel across the different time zones experience two different types of symptoms like insomnia when a person tries to stay awake when the internal clock resists to sleep. The other symptom is that when a person tries to sleep when the internal clock strongly forces the body to stay awake. This is a sort of an important concern for the society and the individuals. Even the tendencies of distorted sleep are noticed in police, nurses, physicians, air traffic controllers and airline pilots and public safety workers that have to work during the night shifts. The results however may be critical. Specificity For about 2 decades, the research on the change in shift work and the has revealed that, shift work has adversely caused fatigue and sleep disturbances among the workers. It has been found that the shift workers have experienced both the lack and difficulties in sleep. This difficulty on the other hand has resulted into excessive fatigue (13,14,15,16). Majority of the shift worker have complained that, they have experienced sleep during the work hours. This have adversely resulted into accidents and mishaps. The misalignment of the social sleep times (forced work) along with the circadian clock is noticed in the shift workers. The reason is that their body remains aligned with the natural clock of night and day cycles, but their work hours distorts the normal functioning of the circadian clock (17, 18, 19). The consequences of the sleep distortion arising due to the high speed travel across time zones leads to psychological disorientation and circadian disruption and as well as trave l disorientation. When a person is moving from one-time zone to another time zone. The body although acclimatized with the previous time zone remains in the previous set synchronized with the internal clock of the body. This undergoes change when the body shifts to a different time zone but still the internal clock stays in the previous time zone. This disrupts the sleep patterns within the people that travel by airlines from one country to another. When the internal clock forces the body to sleep but on the other hand external exposure to light prevents a person to sleep. This creates a situation called jet lag (20, 21, 22). Anxiety, pain and other medical conditions Studies have shown that psychological and the medical conditions have an adverse impact on the health as well as in sleep patterns. The several medical conditions which include chronic pain arising due to arthritis and other several other medical complications involving the premenstrual syndrome, gastroesophageal reflux. Like several other factors that disrupt the sleep patterns, discomfort and pain also tend to reduce and limit the sleep depth and only allow a brief period of sleep between awakenings. Generalization Individuals across all ages, experience the anxiety, depression and stress and it affects the quality of sleep. When an individual gets affected by the anxiety, stress, and depression then the sleep tends to be less deep. Body tends to react to such stimulus of pain because it is programmed to react to pain and body react to such situation by waking up during sleep. On the other hand, stress caused on a daily basis due to everyday work and exposure can also impact on the sleep patterns and quality of sleep. Specificity Rheumatoid arthritis is an autoimmune disorder that can be characterized by swelling and joint pain. In addition, it has been seen in half of the patients suffering from rheumatoid arthritis experience sleep disturbances. The rate is higher and is 2 to 3 times more found in general population. several cross sectional researches have shown that sleep disturbances are closely related with the disruption in sleep quality (23, 24,25). Mediational analysis has shown that, depression acted as a main factor that significantly contributed to the sleep disorder. Also cross sectional study has reported that depression and pain all together play a major role in the self-reported sleep problems in patients suffering from rheumatoid arthritis (26, 27). Sleep disorders also includes the other potential impactors like the depression and anxiety that lead to neuropsychological impairment, suicidal tendencies and drug abuse. Studies have shown that the effects of anxiety and depression are bidirectio nal. Which means sleep quality gets distorted due to depression and stress and on the other hand, both the stress and depression leads to loss of sleep (28, 29, 30 31). Effect on sleep due to chemical substances Several drugs and chemical substances both affect the quantity and quality of sleep. These substances include antihistamines, nicotine, alcohol, caffeine. At the same time antidepressants, alpha blockers and beta blockers tend to disrupt the sleep. Generalization Certain chemicals like adenosine starts to build up inside the brain when body starts to become weak. This although partly, is responsible for the sleep drive. Interestingly, the caffeine levels in the brain tend to stop the buildup of adenosine in brain. Specificity When the body tends to become weak, a chemical called adenosine builds up in brain. The occurrence is similar when body get tired and exhausted. Due to such tendencies, adenosine builds up in brain and taking caffeine reduces the levels of adenosine inside brain and acts as stimulant. This increases alertness and at the same time reduces the sleepiness. The presence of caffeine temporarily blocks the adenosine receptors in the specific parts of the brain (32,33,34). Alcohol on the other hand enhances sleep, because consuming alcohol reduces the oxygen carrying capacity of blood. When less oxygen reaches to the brain, the tendency of sleepiness increases (35,36,37). Comprehensive critique Biases Vandewalle et al. (8) selected 27 subjects genotyped for PER3 VNTR with known dependency of brain response in darkness on circadian rhythm, sleep homeostasis and genotype (non random sampling). This shows a limited scope of study that is targeted for a specific cohort based on the genetic makeup, and not a generalized study. The study only analyses the effect of light of different intensities and frequencies on brain activity, as studied by Functional Magnetic Resonance Imaging (fMRI). Chang et al (2) selected 12 subjects in a randomized crossover design, who fulfilled 2 conditions, 1) Reading e-books before sleep 2) Reading printed books before sleep, both in dimly lit conditions, and analyzed the levels of melatonin in blood plasma, total sleep time, sleep efficiency, and the length of each stage of sleep. However, the study limits itself to the effect of electronic light on the sleep quality of individuals, and does not include the effect of different frequencies of light as well as the time of exposure to light. Validity The validity of the study by Vandewall (8) can be attributed to the usage of fMRI to study the brain activity of the subjects. This allows the mapping of activities to specific areas of the brain like the cortical and sub cortical regions, as well as in fronto?polar, laterals prefrontal and premotor cortex, the intraparietal sulcus, insula, cerebellum and thalamus. However, the brain responses were not mapped to behavioral outcomes that can show how the quality of sleep is affected in the study. Instead, it uses the status of the brain activity as a measure of the effect of exposure to light. Validity of the studies by Chang et al. (2) can be attributed to the usage of the levels of melatonin in blood, to understand the propensity of quality sleep in the subjects. This allows a direct measurement of the possible sleepiness of the subjects, however, the total sleep time, sleep efficiency, and the length of each stage of sleep values were self-reported, and hence can be misreported by the subjects. Reliability Both the studies by Vanderwall et al. (8) and Chang et al. (2) utilize reliable methods in the assessment of the values (fMRI to measure brain activity or blood melatonin to measure propensity to sleep). These were both indirect approaches to understand how sleep quality can be affected. Melatonin levels being positively correlated to Limitations Studies by Vanderwall (8) was limited to low levels of irradiation exposed to the subjects, in addition to the non-inclusion of retinal rod cells in the con-classical response to light. The study was also non ransom, aimed at a cohort of particular genotype. Limitations in studies by Chang et al. (2) include the measurement of blood melatonin levels only on the fifth and final evening in each reading conditions. Also, the duration of the evening sessions of reading were limited to only 4 hours, which is significantly lesser than the average amount of time spent by a teenager in activities before bedtime. Additionally, the brightness setting of the eBook reader was preset at maximum brightness and the books were read in dimly lit conditions, and hence did not analyze the effect of other brightness settings on sleep. Finally, the study did not include the analysis of other electronic devices that emit lights of longer wavelengths, thus failing to study the effect of different spectrum of light on sleep. Sample Size Sample size selected by Vandewall et al. (8) was limited to 27 subjects, while that of Chang et al. (2) was limited to 12 subjects. Both the studies involved a small sample size. Novelty Value The novelty value of the study by Vandewall et al. (8) is the effect of light on brain activity and cognitive responses, which shows how sleepy or alert an individual can be expected to exhibit, under variant exposures to light, based on the circadian rhythm and sleep homeostasis. The novelty value for the study by Chang et al (2) shows how light emitting electronic readers can affect the circadian rhyme, and therefore the sleep quality of individuals. Application or Implications of the research: The findings of the research can be applied in our understanding on how circadian rhythms can be affected by exposure to light of varying duration and intensities, and how in turn that can affect the quality of sleep, level of alertness or sleepiness, and hence as an indicator of performance. Conclusion Therefore, from the study it can be concluded that, quality of sleep gets distorted due to several factors. The major factors include the social jet lag, working hours, the intensity of light and exposure to different wavelengths of light, chemicals, pain, anxiety and depression. Although certain aspects of sleep disorders can be controlled and managed, while the other factors remain unmanageable. Reference Turner JR, Gellman M. Encyclopedia of Behavioral Medicine. 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