Sleep deprivation can affect judgment and reaction time

Neurologist Michael Chee at the Duke-National University of Singapore Graduate School of Medicine says everyone has lapses of attention, but they are more frequent when people are tired. Chee defines these lapses as periods of relatively slow responses, giving a typical driving situation as an example. "If you see a stop sign, if you're fully alert, you'll jam the breaks very quickly, but when you are sleep deprived, you tend to be slower."

Chee studied the timing of different responses by scanning the brains of volunteers who were well-rested. Then he scanned the volunteers again after they had been awake for 24 hours. Each time, he asked them to do a visual task, quickly.

When they were tired, Chee found the subjects could see the visual data. But they couldn't correctly identify what they saw. And they had these lapses more frequently, but with different timing.

"The interesting thing is that these periods when the brain literally goes off-line are intermixed with periods of relatively normal functioning," Chee says. "When you're sleep deprived, there are periods when you're functioning relatively normally, and yet there are periods where you crash. And these can be intermixed over a period of… just seconds."

Chee says the biggest decrease in activity took place in 'control' regions of the brain, areas where judgments are made. He says this could lead to dangerous situations.

"There are a lot of people who push themselves to stay awake just to complete a project or get a job done … with very good intentions," he notes, adding that such a strategy might actually backfire. "As our research shows, there are periods where you're really not processing information properly."

Chee says it's probably better to get some sleep and finish your work when you're rested. But he says researchers are also looking for ways to help people stay alert longer when they have to stay awake.

His research is published in the Journal of Neuroscience.