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SAN FRANCISCO, Oct 10, 2003 (United Press International via COMTEX) -- Skimping on sleep can cost time, money and memory, while getting enough zzzs can
work wonders for retaining lessons learned and restoring those forgotten, human research reveals. The findings should awaken a new regard for slumber as facilitator for carrying out such complex cognitive challenges as acquiring language, scientists told United Press International.
"Our results (confirm) sleep has an important role in consolidating memories and stabilizing them so they are retained for long periods of time," said lead study investigator Daniel Margoliash, professor of organismal biology and anatomy at the University of Chicago.
Though a good night's rest can rescue memories that fade during the course of a day, no mechanism appears capable of repairing the damage caused by slumber cut short, the researchers stated.
Students who get by during the week on two or three hours less sleep than they need lose the slumber-derived benefits forever -- no matter how long they doze on the weekend trying to restore the deficit, warned Matthew Walker, instructor of psychiatry at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston.
"They just don't understand what a tremendous negative impact sleeplessness has on their ability to restore and retain information," Walker, who led a separate sleep study, said in a telephone interview.
The reports, published in the British journal Nature, detail the impact of sleep on learning, exposing previously unknown dynamics of human memory.
In their experiments, Margoliash; Howard Nusbaum, professor of psychology, and Kimberly Fenn trained college students to recognize words from a speech synthesizer. A morning teaching session sent their scores soaring, but by evening their recall ability had deflated. After a night's slumber, however, they again performed at their original best.
"Sleep can rescue memories that have spontaneously deteriorated," said Karim Nader,
Alfred P. Sloan Fellow in psychology at McGill University in Montreal, Canada, who analyzed the findings.
In their investigation, Walker; Robert Stickgold of Beth Israel, and Dr. J. Allan Hobson and Tiffany Brakefield of the Massachusetts Mental Health Center identified three stages of memory processing that sleep and wakefulness may affect. The steps seem to transform vulnerable thoughts and experiences into a more permanent information store, the researchers explained.
In an intriguing twist, they discovered simply recalling the memory leaves it susceptible to disruption and modification. The mechanism permits the brain to alter saved data in the context of ongoing experience, the scientists theorized.
"The finding that reconsolidation occurs in humans is a landmark discovery," Nader told UPI. "This opens up the possibility of treating people who suffer from psychopathologies, such as addiction and post-traumatic stress, by reactivating their ... drug craving and then blocking that memory from being restored."
Potentially, the strategy might lead to a cure in a single session, he added.
The observations come at a time of a growing rebellion against resting by a fast-paced culture that considers slumber a yawner. Researchers calculate the average person has shaved off at least an hour of needed shut-eye a night, ballooning the national sleep debt to 107 billion hours a year.
"We think there's good scientific evidence sleep deprivation has become a serious health problem," Margoliash said in a telephone interview.
Such chronic shortchanging of one of three fundamental human needs carries a host of costly implications, some of which scientists may not yet realize.
"Although for thousands of years, we have known the biological reasons for eating and drinking, we have been in the dark about the 'why' for the third biological need of sleep," Walker told UPI. "The new research is beginning to reveal the answer, which, at least in part, may be related to memory consolidation."
A National Sleep Foundation study estimated sleeplessness takes a $92.5-billion to $107.5-billion bite out of the nation's economy annually, including $15.9 billion in direct health-care and medication expenditures, and the remainder in indirect costs associated with lost productivity and accidental injury and death.
Officials implicate sleep deprivation in more than 100,000 highway crashes a year, 1,500 of them fatal and 71,000 involving injuries.
Fatigue figured in three life-altering events in the past 24 years: the partial reactor meltdown at Three Mile Island in Pennsylvania in 1979, which stunted the nuclear industry; the 1986 explosion of the Space Shuttle Challenger, which took the lives of the first teacher in space and six other astronauts and severely cramped the National Aeronautics and Space Administration's style, and the 1989 spill of millions of gallons of crude oil into pristine waters when the oil supertanker Exxon Valdez ran aground on a reef in Prince William Sound, Alaska.
"In this always-on-the-go society, a lot of people look at sleep as a waste of time, but if we try to cut it, it will be our downfall later," Walker warned. "Look at the Exxon Valdez and the Chernobyl meltdown -- both show the dangers of a lack of sleep."
With the average sleep time slashed by 20 percent in the past 100 years, it is time to wake up to the consequences of a nation that refuses to close its eyes, scientists said.
"The implication is that people's memory and cognitive functions in general will be partially impaired; people will not be working as efficiently as they could and (there will be) a general trend towards decreased general health," Nader said. "We all try to compensate by taking things such as coffee, but you can only compensate for so much impairment."
Although their study dealt specifically with word recognition, the findings may be relevant to other learning, Nusbaum said.
"We have known that people learn better if they learn smaller bits of information over a period of days, rather than all at once," he said. "This research could show how sleep helps us retain what we learn."
The team tested students' understanding of a series of different words muffled by the mechanical, robotic sound of a voice synthesizer. "It is something like learning how to understand someone speaking with a foreign accent," Nusbaum explained.
Those who slept through the night performed as well the next morning as they had immediately after training, which increased their scores by a whopping 20 percent. Subsequent tests showed the effects lasted up to six months.
"When you are trying to learn a new foreign language or a new dialect, we can say with confidence sleep is part of that process," Margoliash told UPI.
In their research, involving 100 subjects ranging in age from 18 to 27 and learning finger-tapping variations, Walker and company identified three stages in the life of a memory.
"To initiate a memory is almost like creating a word processing file on a computer," he explained. "Once the file has been created, if you don't hit the 'save' button before shutting off the computer, it will be lost."
Their new research helps explain the brain process that enables humans to first create the memories and then to stabilize and "save" them. Following the sleep stage, the final phase permits a reshaping of memory, a strategy that could prove useful for treating such psychological ills as post-traumatic stress disorder. Replaying the troublesome memory over time may remove some of its horror, scientists speculated.
"There clearly is an important role sleep has in helping us learn complex tasks," Margoliash concluded. "Mom was right when she admonished us to get a good night's sleep."
Copyright 2003 by United Press International.