Sleeping While Awake: Sleep intrusions during wakefulness and their cognitive consequences

What happens in our brains when we get tired?

Mental fatigue can occur for diverse reasons, through extended periods of wakefulness or following intense cognitive efforts. In other words, fatigue can be both time and use-dependent. My core hypothesis is that both processes are underpinned by local intrusions of sleep in the awake brain. Sleep and wakefulness are not mutually exclusive states.

When animals are sleep deprived, high-amplitude slow waves (SWs), a hallmark of sleep, can be locally observed in awake individuals. These wake SWs have been linked to impaired cognitive performance.

I have further shown that these wake SWs can be observed without sleep deprivation when participants perform demanding tasks. These wake SWs predict objective (errors) and subjective (e.g., mind wandering) markers of attentional lapses. However, the underlying mechanisms driving SWs remain unclear; why do they occur?

How well do they predict the cognitive consequences associated with fatigue?

And can they be externally modulated?To answer these questions, I will first describe the physiological signatures of wake SWs, from single-neuron to whole-brain activity.

Second, I will seek to explain the occurrence of wake SWs by testing their association with the metabolic changes within the brain.

Third, whereas wake SWs have been so far associated with adverse behaviors (lapses of attention), I will examine whether wake SWs could also predict positive outcomes, such as creative insights.

Finally, I will investigate the possibility of modulating wake SWs and improving cognitive performance.Through this project, I will build a novel neurophysiological account of fatigue from the ground up by describing what local sleep is, explaining why it occurs, predicting its adaptative purposes, and modulating how frequently it occurs.

This ambitious research program will generate critical novel insights into the neural mechanisms underlying the everyday phenomenon of fatigue.