Study For Better Grades

         PARIS (AFP) - Researchers may have found the reason why children who go to bed too late often fare badly

                   at school: lack of sleep appears to disrupt functioning of the hippocampus, an area of the brain

                                                                      that formulates new memories.

Reporting Sunday in the journal Nature Neuroscience, Harvard Medical School investigators recruited 28 volunteers, who were either randomly deprived of sleep for two days and a night before carrying out a test, or

who were allowed to sleep normally.

The test involving looking at and remembering a large set of picture slides while the volunteers were screened by fMRI                                   scanner, which gives a 3-D image of blood flow, hence of cerebral activity.

The human guinea pigs were then allowed two full nights of sleep and then performed a second test in which they were                                         asked to spot the original slides in a batch that included new pictures.

The sleep-deprived group did slightly worse in the first test than the sleepers, but did considerably better than

                                                                            them in the second.

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

      than among their counterparts. This had a knock-on effect on other parts of the brain that are linked to alertness,

                                                                     the brainstem and thalamus.

                      Previous research has 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 behavioural capacity for committing new experiences to memory," says the paper.

                   "It therefore appears that sleep before learning is critical in preparing the human brain for

         next-day memory formation -- a worrying finding considering society's increasing erosion of sleep time."