***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Learning of a procedural motor-skill task is known to progress through a series of unique memory stages . Performance initially improves during training , and continues to improve , without further rehearsal , across subsequent periods of sleep . Here , we investigate how this delayed sleep-dependent learning is affected when the task characteristics are varied across several degrees of difficulty , and whether this improvement differentially enhances individual transitions of the motor-sequence pattern being learned . We report that subjects show similar overnight improvements in speed whether learning a five-element unimanual sequence ( 17.7 % improvement ) , a nine-element unimanual sequence ( 20.2 % ) , or a five-element bimanual sequence ( 17.5 % ) , but show markedly increased overnight improvement ( 28.9 % ) with a nine-element bimanual sequence . In addition , individual transitions within the motor-sequence pattern that appeared most difficult at the end of training showed a significant 17.8 % increase in speed overnight , whereas those transitions that were performed most rapidly at the end of training showed only a non-significant 1.4 % improvement . Together , these findings suggest that the sleep-dependent learning process selectively provides maximum benefit to motor-skill procedures that proved to be most difficult prior to sleep OBJECTIVE To study the associations between sleep quality /quantity and performance in auditory/visual working memory tasks of different load levels . METHOD Sixty schoolchildren aged 6 to 13 years from normal school classes voluntarily participated . Actigraphy measurement was done during a typical school week for 72 consecutive hours . It was timed together with the working memory experiments to obtain information on children 's sleep during that period . The n-back task paradigm was used to examine auditory and visual working memory functions . RESULTS Lower sleep efficiency and longer sleep latency were associated with a higher percentage of incorrect responses in working memory tasks at all memory load levels ( partial correlations , controlling for age , all p values < .05 , except in visual 0-back and auditive 2-back tasks ) ; shorter sleep duration was associated with performing tasks at the highest load level only ( partial correlations , controlling for age , p < .05 ) . Also in general linear models ( controlling for age , gender , and socioeconomic status ) , sleep efficiency ( F = 11.706 , p = .050 ) and latency ( F = 3.588 , p = .034 ) were significantly associated with the mean incorrect response rate in auditory working memory tasks . CONCLUSIONS Sleep quality and quantity affect performance of working memory tasks in school-age children . In children with learning difficulties the possibility of underlying sleep problems should be excluded The endogenous circadian oscillator in mammals , situated in the suprachiasmatic nuclei , receives environmental photic input from specialized subsets of photoreceptive retinal ganglion cells . The human circadian pacemaker is exquisitely sensitive to ocular light exposure , even in some people who are otherwise totally blind . The magnitude of the re setting response to white light depends on the timing , intensity , duration , number and pattern of exposures . We report here that the circadian re setting response in humans , as measured by the pineal melatonin rhythm , is also wavelength dependent . Exposure to 6.5 h of monochromatic light at 460 nm induces a two-fold greater circadian phase delay than 6.5 h of 555 nm monochromatic light of equal photon density . Similarly , 460 nm monochromatic light causes twice the amount of melatonin suppression compared to 555 nm monochromatic light , and is dependent on the duration of exposure in addition to wavelength . These studies demonstrate that the peak of sensitivity of the human circadian pacemaker to light is blue-shifted relative to the three-cone visual photopic system , the sensitivity of which peaks at approximately 555 nm . Thus photopic lux , the st and ard unit of illuminance , is inappropriate when quantifying the photic drive required to reset the human circadian pacemaker BACKGROUND No prospect i ve studies exist on the relationship between sleep problems  early in life and subsequent alcohol use . Stimulated by the adult literature linking sleep problems to the subsequent onset of alcohol use disorders in some adults , we examined whether sleep problems in early childhood predicted the onset of alcohol and other drug use in adolescence and whether such a relationship was mediated by other known predictors of this relationship , namely , attention problems , anxiety/depression , and aggression in late childhood . METHODS This study is part of an ongoing longitudinal study of the development of risk for alcohol and other substance use disorders . Study participants were 257 boys from a community-recruited sample of high-risk families . RESULTS Mothers ' ratings of their children 's sleep problems  at ages 3 to 5 years significantly predicted an early onset of any use of alcohol , marijuana , and illicit drugs , as well as an early onset of occasional or regular use of cigarettes by age 12 to 14 . Additionally , although sleep problems in early childhood also predicted attention problems and anxiety/depression in later childhood , these problems did not mediate the relationship between sleep problems and onset of alcohol and other drug use . CONCLUSIONS This is , to our knowledge , the first study that prospect ively examines the relationship between sleep problems and early onset of alcohol use , a marker of increased risk for later alcohol problems and alcohol use disorders . Moreover , early childhood sleep problems seem to be a robust marker for use of drugs other than alcohol . Implication s for the prevention of early alcohol and other drug use are discussed OBJECTIVE To investigate the relationship between the presence of a television set , a gaming computer , and /or an Internet connection in the room of adolescents and television viewing ,  computer game playing , and Internet use on the one h and , and time to bed , time up , time spent in bed , and overall tiredness in first- and fourth-year secondary -school children on the other h and . METHODS A r and om sample of students from 15 schools in Fl and ers , Belgium , yielded 2546 children who completed a question naire with questions about media presence  in bedrooms ; volume of television viewing , computer game playing , and Internet use ; time to bed and time up on average weekdays and average weekend days ; and questions regarding the level of tiredness in the morning , at school , after a day at school , and after the weekend . RESULTS Children with a television set in their rooms went to bed significantly later on weekdays and weekend days and got up significantly later on weekend days . Overall , they spent less time in bed on weekdays . Children with a gaming computer in their rooms went to bed significantly later on weekdays . On weekdays , they spent significantly less time in bed . Children who watched more television went to bed later on weekdays and weekend days and got up later on weekend days . They spent less time in bed on weekdays . They reported higher overall levels of being tired . Children who spent more time playing computer games went to bed later on weekdays and weekend days and got up later on weekend days . On weekdays , they actually got up significantly earlier . They spent less time in bed on weekdays and reported higher levels of tiredness . Children who spent more time using the Internet went to bed significantly later during the week and during the weekend . They got up later on weekend days . They spent less time in bed during the week and reported higher levels of tiredness . Going out was also significantly related to sleeping later and less . CONCLUSION Concerns about media use should not be limited to television . Computer game playing and Internet use are related to sleep behavior as well . Leisure activities that are unstructured seem to be negatively related to good sleep patterns . Imposing more structure ( eg , end times ) might reduce impact 
    Output:
    
Rates of change were negative across age , sex and day type categories , but varied according to region , with Europe , the USA , Canada and Asia showing decreases and Australia , the UK and Sc and inavia showing increases .
Over the last 103 years , there have been consistent rapid declines in the sleep duration of children and adolescents