An hour's nap can dramatically boost and restore brain power, according to a new study from the University of California reported Monday.

The study, from the department of psychology at UC Berkeley, suggests taking a brief siesta not only refreshes the mind, but can also make you smarter.

And those who work long days without a rest become more sluggish, the study said. Pulling an all-nighter, for example, decreased the brain's ability to learn by nearly 40 percent in those observed.

"Sleep not only rights the wrong of prolonged wakefulness but ... it moves you beyond where you were before you took a nap," said Matthew Walker, the study's lead investigator.

Walker and his team will go on to investigate whether the reduction of sleep experienced by people as they get older is related to the documented decrease in our ability to learn as we age.

The findings come as other reports cited a study which linked insomnia and sleep deprivation to the shrinking of grey matter in the brain.

The research, led by Dr. Ellemarije Altena at the University of Cambridge, found that chronic insomnia compromised brain capacity and had consequences for decision-making.