Thursday, October 17, 2019

Detection of artefacts in sleep studies data Literature review

Detection of artefacts in sleep studies data - Literature review Example The studies have yielded different findings and this implies that scientists are yet to comprehend the phenomenon fully. However, empirical studies have established that sleep is important for enhancing normal and healthy performance of physical and mental aspects of the human body. In addition to these findings, sleeping process has been exclusively studied to establish the various stages involved and the brains level of activity during the process. This paper investigates the various stages of sleep and the role of sleep to human beings. Recent scientific studies have discredited the common misconception that regarded sleep as a dormant mental state. Scientists have established that the brain maintains a high level of activity during sleep. In addition, sleep influences the physical and mental functioning of our bodies in various ways that continue to attract numerous studies in order to enhance our understanding about the phenomenon (Baddely, 2000). Nerve-triggering chemicals call ed neurotransmitters determine whether we are awake or sleep by stimulating various groups of nerve cells and neurons in the brain. In the brainstem that links the brain with the spinal cord, neurons produce various neurotransmitters such as norepinephrine and serotonin that ensures that some parts of the brain remain active while in a wakeful state. When we begin falling asleep, neurons at the base of the brain start signalling and they suppress the neurotransmitters that keep us awake (Espana and Scammel, 2011). According to Espana and Scammel (2011), the state of wakefulness is enhanced by neurons present in the midbrain, pons, and in the posterior hypothalamus that produce various types of neurotransmitters, including histamine, serotonin, dopamine, acetylcholine, orexin and norepinephrine. The neurotransmitters that determine wakefulness and sleep diffuse actively in the brain, activating the targeted regions of in the cortex and forebrain. The reciprocal inhibition that occurs between sleep and wake controlling regions in the brain helps in the production of sleep and wakefulness with quick transitions between the states (Espana and Scammel, 2011, p 847). Scientists use three basic measures to classify sleep into different stages. The three measures include the gross brain activity, muscle tone and the eye movement (Carlson, 2001). Electroencephalograph (EEG) machine detects gross brain wave activity from which it produces summary of electrical action from the brain. The muscle tone is measured using an electromyogram (EMG) machine while eye movements during sleep are recorded using electro- oculogram (EOG). According to Harvey and Bruce (2006), electroencephalograph (EEG) is the most widely applied measure of distinguishing the different sleep stages while electromyogram (EMG) and electro-encephalograph are crucial in differentiating rapid eye movement (REM) sleep from the other types. Two different states alternate in cycles when a person is asleep and they portray the varying levels of neural activity in the brain. The states that constitute sleep are non-rapid eye movement (NREM) and rapid eye movement (REM) (Zhang, 2004). According to Zhang (2004), each of these states is associated with a unique and different form of brain wave activity. Non -rapid eye movement (NREM) is subdivided into four different stages that include stage 1, 2, 3 and 4. Therefore, typical sleep is made up of five stages, where NREM constitute 75% and the rest is REM (Carlson, 2001). The stages of REM sleep and NREM

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