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A sigmoid function is any mathematical function whose graph has a characteristic S-shaped or sigmoid curve. A common example of a sigmoid function is the logistic function , which is defined by the formula: [ 1 ]
During slow-wave sleep, there is a significant decline in cerebral metabolic rate and cerebral blood flow. The activity falls to about 75 percent of the normal wakefulness level. The regions of the brain that are most active when awake have the highest level of delta waves during slow-wave sleep. This indicates that the rest is geographical.
Homeostatic functions, especially thermoregulation, occur normally during non-REM sleep, but not during REM sleep. Thus, during REM sleep, body temperature tends to drift away from its mean level, and during non-REM sleep, to return to normal. Alternation between the stages therefore maintains body temperature within an acceptable range. [10]
NREM Stage 1 (N1 – light sleep, somnolence, drowsy sleep – 5–10% of total sleep in adults): This is a stage of sleep that usually occurs between sleep and wakefulness, and sometimes occurs between periods of deeper sleep and periods of REM. The muscles are active, and the eyes roll slowly, opening and closing moderately.
Sleep plays a vital role in regulating metabolism and appetite. When sleep deprived, the metabolic system will be out of balance, which will ultimately affect the dietary choices people make. Teens who are sleep deprived crave more carbohydrates. Sleep deprivation is a risk factor for obesity among young adults. [7] [medical citation needed]
The sleeping brain has been shown to remove metabolic end products at a faster rate than during an awake state, by increasing the flow of cerebrospinal fluid during sleep. [94] The mechanism for this removal appears to be the glymphatic system , a system that does for the brain what the lymphatic system does for the body.
Logistic activation function. The activation function of a node in an artificial neural network is a function that calculates the output of the node based on its individual inputs and their weights. Nontrivial problems can be solved using only a few nodes if the activation function is nonlinear. [1]
Parasomnias are sleep behaviors that affect the function, quality, or timing of sleep, caused by a physiological activation in which the brain is caught between the stages of falling asleep and waking. The autonomous nervous system, cognitive process, and motor system are activated during sleep or while the person wakes up from sleep.