You’ve probably heard people say they enjoy running because it lets them switch off. Perhaps you feel that way yourself. Well recent research in mice suggests there may actually be a scientific basis for this, because brain activity really does decrease when you’re performing a simple, repetitive action. What’s more, while running may tire your body out, such exercise might actually reduce your brain’s need for sleep.
Being awake and being asleep aren’t two mutually exclusive, uniform states. At times you can be more deeply asleep or more wide awake than others, and the boundary between the two can be blurred. Your normal behaviour, such as the ability to react quickly to unexpected events, deteriorates as you stay awake beyond your regular bedtime. We don’t know exactly why this is but it may be that parts of your brain go to sleep even when you’re technically awake. But with the right motivation, we can also force ourselves to stay awake and even restore our performance temporarily.
How long we need to sleep or can stay awake for depends to some extent on our genes, but evidence suggests they are also affected by what activities we do while we’re awake. Surprisingly, we still don’t know what is it about being awake that puts pressure on our bodies to sleep, but scientists often refer to is as “Process S”. Like an hourglass, the levels of Process S indicate how long we’ve been awake or asleep and how likely we are to fall asleep or wake up at any given moment.
Recent evidence suggests that sleep is initiated not by the brain as a whole but by local networks of neurons that were used more while awake. My colleagues and I wondered if parts of the brain responsible for certain behaviours had more of an affect on our ability to stay awake than others.