Study shows importance of sleep for optimal memory functioning

Harvard researchers have tracked fatigue's footsteps on the human brain, showing that sleeplessness impairs the ability to learn new information and that abnormal brain function, not reduced alertness, is the cause.

The study, released in the journal Nature Neuroscience, adds a new wrinkle to the unfolding story of the importance of sleep for memory function and builds on earlier studies that show that sleep deprivation after an event also impairs memory formation.

The study found that student volunteers who had been awake for 35 hours before viewing images performed an average of 19 percent worse remembering those images two days later, after catching up on their sleep.

Further, using functional magnetic resonance imaging (MRI), the researchers traced the initial learning impairment to the hippocampus, a part of the brain researchers described as its "short-term memory," analogous to a computer's RAM or cache memory. Activity in the hippocampus was significantly decreased among sleep-deprived volunteers in the study.

The study's senior author, Matthew Walker, an assistant professor of psychology in Harvard Medical School's Psychiatry Department, said the study's most important scientific finding is that the impairment comes from impaired brain functioning - almost as if a temporary lesion had formed on the hippocampus - rather than merely from reduced alertness and an inability to take in the images.