[www.cnn.com]

"(CNN) -- Are you a truck driver or shift worker planning to catch up on some sleep this weekend?

Cramming in extra hours of shut-eye may not make up for those lost pulling all-nighters, new research indicates.

The damage may already be done -- brain damage, that is, said neuroscientist Sigrid Veasey from the University of Pennsylvania.
Alzheimer's & Sleep
The widely held idea that you can pay back a sizeable "sleep debt" with long naps later on seems to be a myth, she said in a study published this week in the Journal of Neuroscience.

Long-term sleep deprivation saps the brain of power even after days of recovery sleep, Veasey said. And that could be a sign of lasting brain injury.
Veasey and her colleagues at the University of Pennsylvania medical school wanted to find out, so, they put laboratory mice on a wonky sleep schedule that mirrors that of shift workers.

They let them snooze, then woke them up for short periods and for long ones.
Then the scientists looked at their brains -- more specifically, at a bundle of nerve cells they say is associated with alertness and cognitive function, the locus coeruleus.

They found damage and lots of it.

"The mice lose 25% of these neurons," Veasey said."