Grant: Travel Awards - Institute Community Support

Old age is a time to enjoy the fruits of a lifetime of intellectual, emotional and interpersonal growth, but for too many, these pleasures are taken away by the slow and steady advance of cognitive decline. To understand the causes of cognitive decline is the first step in treating and preventing this scourge. To this end, researchers have turned their attention to sleep. Sleep quality rapidly deteriorates with age. In light of the mounting evidence that sleep's role is to preserve memories, it is becoming evident that sleep problems in old age contribute to cognitive decline. Recent evidence suggests that sleep solidifies memories through rhythmic bursts of brain activity during sleep, known as sleep oscillations. The most important of these sleep oscillations are spindles and slow waves. Together, they are believed to precisely synchronize the activity of the brain's billions of cells so that new memories are transferred to long-term storage. When this process goes awry, the brain loses its ability to learn and adapt. Much research has shown that indeed, spindles and slow waves are important for preserving memories, but none has examined whether it is really the synchronization of these two oscillations that is essential. Our study has shown just this. By observing the sleep brain activity of 11 good sleepers after they performed either a word learning task or a non-learning task, we showed that there is an increase in the degree to which spindles and slow waves are synchronized, or coupled, after an intense bout of learning. Furthermore, those sleepers who retained the most words when we tested them the next morning also showed the greatest degree of coupling. This is the first evidence that the coupling of spindles and slow waves is important for memory. The detection of this disruption in at-risk individuals could provide an early sign of cognitive decline, allowing efficient targeting of preventative treatment and the extension of mentally healthy old age.