Sleep Lets BrainFile Memories

To sleep.Perchanceto file?Findings published online this week by the proceedings of the NationalAcademy of Sciences further support the theory that the brain organizes

and stows memoriesformed during the day while the rest of the body is catching zzz's.

Gyorgy Buzsaki of Rutgers University and his colleagues analyzedthe brain waves of sleeping rats and mice. Specifically,they examined theelectrical activity emanating

（散发）from thesomatosensory（耳、目、口等以外的）neocortex（新大脑皮层）(an area that processes sensory information) and the hippocampus（海马）,which is

a center forlearning and memory. The scientists found that oscillations in brain waves fromthe two regions appear to be intertwined.So-called sleep spindles (bursts of

activity from theneocortex)were followed tens of milliseconds later by beats in the hippocampusknown as ripples.The team posits that this interplay between the two brain

regions is a keystep in memory consolidation.

A second study,alsopublished online this week by the proceedings of the National Academy ofSciences,links age-associated memory decline to high glucose levels.

Previous researchhad shown that individuals with diabetes（糖尿病，多尿症）suffer from increased memory problems.In the new work,Antonio Convitof New York

University School of Medicine and his collaborators studied 30people whose average age was 69 to investigate whether sugar levels,which tendto increase with age,affect

memory in healthypeople as well.The scientists administered recall tests, brain scans（细看，审视，浏览，扫描）and glucose tolerancetests, which measure how quickly

sugar is absorbedfrom the blood by the body's tissues.Subjects with the poorest memoryrecollection,the team discovered,also displayed the poorest glucosetolerance.In

addition,their brainscans showed more hippocampus shrinkage than those of subjects better able toabsorb blood sugar.

" Our studysuggests that this impairment（损害、损伤）may contribute to the memory deficits （赤字、不足额）that occur as people age."Convit says."And it raises the

intriguingpossibility that improving glucose tolerance could reverse some age-associatedproblems in cognition."Exercise and weight control can help keep glucoselevels in

check（阻止、制止）,so there may be one more reasonto go to the gym.

What is therelation of memory to glucose tolerance,as is indicated by a research mentionedin Paragraph 4?

A.People with poormemory have high glucose tolerance.

B.People with goodmemory have low glucose tolerance.

C.Memory level hasnothing to do with glucose tolerance.

D.The poorer thememory,the poorer glucose tolerance.