This they claim accounts for the feeling of being "half asleep" which causes forgetfulness and small errors such as misplacing keys or putting the milk in the cupboard or the cereal in the fridge.
The team at the University of Wisconsin, who measured electrical waves in the brain, discovered that some nerve cells in tired yet awake individuals can briefly go "offline".
Professor Chiara Cirelli, a psychiatrist and author of the study, said: "Even before you feel fatigued, there are signs in the brain that you should stop certain activities that may require alertness.
"Specific groups of neurons may be falling asleep, with negative consequences on performance."
Until now, scientists thought that sleep deprivation generally affected the entire brain. Electroencephalograms (EEGs), that measure electrical activity in the brain, show network can detect whether neurons in the brain are on or off.
Prof Cirelli said: "We know that when we are sleepy, we make mistakes, our attention wanders and our vigilance goes down.
"We have seen with EEGs that even while we are awake, we can experience shorts periods of 'micro sleep'."
She said periods of micro sleep were thought to be the most likely cause of people falling asleep at the wheel while driving.
However, the new research found that even before that stage, brains are already showing sleep-like activity that impairs them.
The researchers inserted probes into specific groups of neurons in the brains of freely-behaving rats. After the rats were kept awake for prolonged periods, the probes showed areas of "local sleep" despite the animals' appearance of being awake and active.
Prof Cirelli said: "Even when some neurons went offline, the overall EEG measurements of the brain indicated wakefulness in the rats."
She said there were behavioural problems caused by local sleep episodes.
"When we prolonged the awake period, we saw the rats start to make mistakes," she said.
Read more at The Telegraph
No comments:
Post a Comment