Mechanisms and Functions of Brain Oscillations during Human Non-Rapid-Eye-Movement (NREM) Sleep: a Functional Neuroimaging Approach

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During sleep in humans, brain function is characterized by rhythmic activities of large numbers of neurons. These rhythmic activities - also called brain oscillations - can be detected through electrodes placed on the scalp during sleep (with an electroencephalogram, or EEG). Brain oscillations of sleep are mostly produced during a sleep stage called non-rapid-eye-movement (NREM) sleep, which accounts for approximately 75% of total sleep in adults. Two main types of brain oscillations during sleep are described: waxing-and-waning oscillations called sleep spindles, and high amplitude oscillations called slow waves. Past research has used techniques of brain imaging to show that activity is intense in certain regions of the brain during sleep spindles and slow waves, which demonstrates that the brain still remains very active during sleep. Recent research has also indicated that brain oscillations of sleep, especially spindles, prevent external stimulation (such as noise) from disrupting the stability of sleep. Brain oscillations are thus the pillars of brain activity during sleep, and are therefore likely to play an essential role in the understanding of the functions of sleep. In this project, our objective it to evaluate how brain oscillations of sleep help us to learn and remember new information during the day. In particular, we will used sophisticated brain imaging techniques (in particular functional magnetic resonance imaging, or fMRI) to study brain oscillations during sleep and relate them to memory performance during the daytime. We will also study how brain oscillations during a sleep following a night of sleep deprivation will help us to recover our abilities to learn information during the next day. The current project will thus shed new light on the mechanisms of important functions of sleep, such as the maintenance of optimal learning and memory performances. The project will also bring new insight on the mechanisms and functions of brain oscillations during sleep, which constitute examples of spontaneous activities of the brain.