Dozing Off or Going Off Line?

If, like us, you’ve ever “misplaced” your keys or stuck the milk in the cupboard and the cereal in the refrigerator, we have good news for you. According to new research, chances are you’re not going mad, or showing signs of early Alzheimer’s – your brain may simply have been taking a nap!

The study published this week in Nature suggests that certain napping neurons in an otherwise awake brain may be responsible for the attention lapses, poor judgment, mistake-proneness and irritability that we’ve all experienced when we haven’t had enough sleep.

Doctors at the University of Wisconsin-Madison say they 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.

Even before you feel fatigued, there are signs in the brain that you should stop certain activities that may require alertness,” says Dr. 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.”

Until now, scientists thought that sleep deprivation generally affected the entire brain. EEGs typically show network brain-wave patterns typical of either being asleep or awake.  Micro sleep, a term used to describe momentary periods of sleep that can occur at any time, typically without significant warning was thought to be the most likely cause of accidents due to falling asleep at the wheel while driving.

But the new research found that even before that stage, brains are already showing sleep-like activity that impairs them.  In the current study, researchers inserted probes into 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.
And there were behavioral consequences to the local sleep episodes. When they kept the rats up beyond their bedtime, the rats started to make mistakes. When challenged to do a tricky task, such as reaching with one paw to get a sugar pellet, they began to drop the pellets or miss in reaching for them, indicating that a few neurons might have gone off line.

This activity happened in few cells,” Cirelli adds. “Out of 20 neurons we monitored in one experiment, 18 stayed awake. From the other two, there were signs of sleep—brief periods of activity alternating with periods of silence.”

So, the next time you do something dumb, don’t blame yourself, just tell people your brain was off-line!