<P> Sleep deprivation has been shown to have a detrimental effect on cognitive tasks, especially involving divergent functions or multitasking . It also has effects on mood and emotion, and there have been multiple reports of increased tendency for rage, fear or depression with sleep debt . However, some of the higher cognitive functions seem to remain unaffected albeit slower . Many of these effects vary from person to person i.e. while some individuals have high degrees of cognitive impairment with lack of sleep, in others, it has minimal effects . The exact mechanisms for the above are still unknown and the exact neural pathways and cellular mechanisms of sleep debt are still being researched . </P> <P> A sleep disorder, or somnipathy, is a medical disorder of the sleep patterns of a person or animal . Polysomnography is a test commonly used for diagnosing some sleep disorders . Sleep disorders are broadly classified into dyssomnias, parasomnias, circadian rhythm sleep disorders, and other disorders including ones caused by medical or psychological conditions and sleeping sickness . Some common sleep disorders include insomnia (chronic inability to sleep), sleep apnea (abnormally low breathing during sleep), narcolepsy (excessive sleepiness at inappropriate times), cataplexy (sudden and transient loss of muscle tone), and sleeping sickness (disruption of sleep cycle due to infection). Other disorders that are being studied include sleepwalking, sleep terror and bed wetting . </P> <P> Studying sleep disorders is particularly useful as it gives some clues as to which parts of the brain may be involved in the modified function . This is done by comparing the imaging and histological patterns in normal and affected subjects . Treatment of sleep disorders typically involves behavioral and psychotherapeutic methods though other techniques may also be used . The choice of treatment methodology for a specific patient depends on the patient's diagnosis, medical and psychiatric history, and preferences, as well as the expertise of the treating clinician . Often, behavioral or psychotherapeutic and pharmacological approaches are compatible and can effectively be combined to maximize therapeutic benefits . </P> <P> A related field is that of sleep medicine which involves the diagnosis and therapy of sleep disorders and sleep deprivation, which is a major cause of accidents . This involves a variety of diagnostic methods including polysomnography, sleep diary, multiple sleep latency test, etc . Similarly, treatment may be behavioral such as cognitive behavioral therapy or may include pharmacological medication or bright light therapy . </P>

Part of the brain responsible for regulation of sleep and wakefulness