Have you ever noticed that if you did not have enough sleep or your sleep was disrupted the night before, you will not function at your mental optimum the day after? If you are a student, you feel that you can't pay enough attention in class. If you are a working adult, you tend to make more mistakes than usual. Recently, scientists have evidence that lack of sleep is essential for proper learning, memory as well as for every day mental work.

A lack of sleep appears to disrupt the functioning of the hippocampus, an area of the brain that forms new memories.

The latest of the medical journal Nature Neuroscience reported on Harvard Medical School investigators who recruited 28 volunteers who were either randomly deprived of sleep for two days and a night or who were allowed to sleep normally.

They looked at and tried to remember a large set of pictures while a scanner screened them, mapping their blood flow, and hence cerebral activity.

The subjects were then allowed two full nights of sleep before a second test in which they had to spot the original slides in a batch that included new pictures.

The sleep-deprived group did worse in the first test than those who had slept. But in the second test, those who had been sleep-deprived did much better than those who had earlier slept.

The scanner showed that in the first test, hippocampus activity among the sleep-deprived was far lower.

Previous research had found that sleep after learning is vital for consolidating memory, but hard evidence has, until now, been lacking as to the effects of lack of sleep before a memory is created.

"These results demonstrate that an absence of prior sleep substantially compromises the neural and behavioral capacity for committing new experiences to memory," said the study.

"It therefore appears that sleep before learning is critical in preparing the human brain for next-day memory formation."

In a separate study work on rats, by a team from Princeton University found that a lack of sleep affected the hippocampus. It found that the stress hormone corticosterone caused the effect. The researchers compared animals which were deprived of sleep for 72 hours with others which were not. Those who missed out on rest had higher levels of corticosterone and produced significantly fewer brain cells in a particular region of the hippocampus. When the animal's corticosterone levels were kept at a constant level, the reduction cell proliferation ended. This may explain why people who experience lack of sleep face concerntration problems and other difficulties.

If you're having trouble falling asleep at night, head to the kitchen and reach for some kiwifruit. A study by Taipei Medical University has found that eating two kiwifruits an hour before going to bed can improve your sleep quality by as much as 40 percent.

Professor Jen-Fang Liu of the university's School of Nutrition and Health Science studied the sleep pattern of 29 subjects with diagnosed sleeping difficulties over four weeks. She found that the kiwifruit diet decreased Sleep Onset Latency (SOL) by an average of 38.7 percent. SOL is the time it takes a person to fall asleep after going to bed. The participants also reported waking up less during the night.

And here's a handy tip; If you find it a hassle to peel the kiwifruit, simply cut it in half and scoop the contents out with a spoon.

Other alternatives to a better night's sleep include a cup of chamomile tea to soothe frazzled nerves, a warm glass of milk after a warm bath or just reading a book until you feel you are ready for bed. If you are living with a partner, you can also ask him or her to give you a light massage to ease the day's tensions.

Changing your sleeping schedule, either bringing it forward or backward, dimming the lights or having soft music in the background may also induce sleep.Doing light mental work like a crossword puzzle or jigsaw puzzle may also help.

It pays to get a good night's sleep for optimum learning and other memory work. A good night's rest also mean less mistakes at work. So there you have it, a good night's sleep makes you healthy, wealthy and wise.