Researchers at the University of Wisconsin-Madison have found that some nerve cells in a sleep-deprived yet awake brain can briefly go ‘off-line’ into a sleep-like state, while the rest of the brain appears awake, leading to mistakes.
"Even before you feel fatigued, there are signs in the brain that you should stop certain activities that may require alertness," said Chiara Cirelli, professor of psychiatry at the School of Medicine and Public Health.
"Specific groups of neurons may be falling asleep, with negative consequences on performance,” added Cirelli.
Until now, scientists thought that sleep deprivation generally affected the entire brain. Electroencephalograms (EEGs) show network brain-wave patterns typical of either being asleep or awake.
"We know that when we are sleepy, we make mistakes, our attention wanders and our vigilance goes down," said Cirelli.
"We have seen with EEGs that even while we are awake, we can experience shorts periods of 'micro sleep',” added Cirelli.
Periods of micro sleep were thought to be the most likely cause of people falling asleep at the wheel while driving, said Cirelli.
But the new research found that even before that stage, brains are already showing sleep-like activity that impairs them, she said.
The study is detailed in the current issue of Nature.