How many hours of sleep do you get every night? If you're like most of us, the answer is not enough. Scientists have found that getting enough rest will help you remember more than just where you last put your car keys.

The study of 60 healthy young adults found that lack of sleep had a negative effect on the brain's ability to sort through and retain recent memory.

Dr. Jeffrey Ellenbogen helped conduct the study and says there is a correlation between sleep and memory. "Sleep is actually actively engaging the memory and making it stronger."

Medical researchers at Harvard University and the University of Pennsylvania told some students to sleep before they were tested on what they had just learned. Other students did not sleep. Those who slept had sharper memories than those who stayed awake.

"Getting a good night's sleep stabilized and strengthened the memory."

The link between sleep and memory was first established decades ago. But the theory has remained controversial because researchers are still not sure how the brain retains memory. Without that evidence, many scientists say they don't know conclusively how sleep affects the process. This new study of 'declarative memory,' which is the ability to recall facts and events, does show marked improvement after sleep.

A survey by the National Sleep Foundation in the United States found that teenagers are among the most sleep deprived ... and most Americans between the ages of 18 and 54 sleep an average of six hours a night. Health experts say seven to eight hours of rest is what most of us need to face the next day.