Decreased brain waves during sleep predict memory decline in older adults, reports a study published online this week in Nature Neuroscience. This study helps explain why older people’s memories do not benefit as much from sleep as younger individuals, and suggests a possible intervention to help boost memory maintenance in the elderly.
Getting a good night’s sleep is thought to help people to remember events better. Evidence from young adults suggests that the amount of non- rapid eye movement sleep, or slow wave sleep, correlates with the degree of memory consolidation seen during sleep. Human adults are known to get worse at memory tasks with age, and aging is correlated with the deterioration of certain brain areas that are important in generating these slow waves.
Matthew Walker and his colleagues instructed healthy young and older adults to learn a set of words. They then tested subjects’ memory either immediately after learning the list or after a night of sleep. They found that the memories of older individuals were much worse than younger ones, and the older subjects also had varying degrees of brain matter loss in the medial prefrontal cortex (mPFC) - an area known to be important for slow wave generation during sleep. The authors report that age-related loss in mPFC grey matter predicts the loss of slow wave sleep in the older subjects, and that this loss of slow wave sleep in turn is predictive of the age-related decline of memory retention.