6.03.2007

Researchers Focus on Eyes: Memory and Sleep Deprivation
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Although it’s true that sleep deprivation can lead to short-term memory loss, new research suggests it’s not that our minds become too tired to absorb new material, but that the information doesn’t get relayed past the eyes.

Experiments show that visual processing is impaired in the sleep-deprived, scientists reported last month.

Those short on sleep can only see and take in a small number of objects at a time. Anything over a certain threshold is lost.

“When people are sleep-deprived, they may not be seeing what they think they should be seeing, and it appears that this is what contributes to memory declines following sleep deprivation,” said Dr. Michael Chee, a neuroscientist at the National University of Singapore Graduate Medical School. He headed the team of researchers from his institution and Duke University.

The study involved 30 healthy volunteers whose memory was tested after a regular night’s sleep and after going 24 hours with no sleep.

“We generally think of memory decline as a result of faulty storage of information,” Chee said. “However, if the information is not properly handled by the visual system, either as a result of a failure to direct attention appropriately or a failure of visual areas (of the brain) to process what is seen, you can forget about the later stages of information consolidation and storage.”

Chee’s findings were published online by the Proceedings of the National Academy of Sciences.

He noted that a small group of sleep-deprived volunteers who had better performance in the tests were more able to tune out distractions, “but even they suffered from compromised visual attention and processing.”

In his next round of experiments, Chee wants to use brain imaging during tests to see if there are structural differences in the brains of people who are more or less susceptible to attention deficits from sleep deprivation.

Individuals who are less susceptible might make better candidates for long shifts at air traffic control centers, power plants or emergency dispatch centers, the researcher suggests.

And while we’re talking about attention deficits, can we not talk about them in a crowded car?

Australian researchers – including some who first noted that a driver who chats on a cell phone quadruples his risk of ramming another car – now say that driving with passengers substantially increases the risk of a serious crash, no matter how old the driver is. This is especially the case when driving with two or more passengers.

“Drivers with passengers were more than 60 percent more likely to have a motor-vehicle crash resulting in hospitalization, irrespective of their age group,” said Dr. Susanne McEvoy, lead investigator for the project at the George Institute for International Health in Sydney.

“The likelihood of a crash was more than doubled in the presence of two or more passengers,” McEvoy added.

The distraction level was not as great as that reported from phone use. But a lot more people drive with passengers than talk on phones in transit, so the toll from this kind of distraction is likely higher.

In addition, the researchers said the distraction risk is probably just one part of the equation for those most easily diverted – teenagers. They run extra risks from riding with other teens because peer pressure and showing off make them do stupid things.

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