What happens to the brain when we're sleepy?

Kat Arney put this to neuroscientist Laura Ford, from the University of Cambridge...

Laura - The way that we look at this is we actually do sleep deprivation studies so that's exactly what it sounds like. We asked people to come in and volunteer to just be deprived from sleep for a couple of days because no scientists like to do that to people.

Kat - Why would you do that? That sounds awful.

Laura - I know.

Chris - Loads of parents would sign up for that.

Laura - Exactly. They can be our great case studies. So the idea is that we invite you to come in. so this is why parents wouldn't qualify because they need to be well rested when they start because we need.

Chris - That rules me out then, yeah.

Laura - Yeah. We need a good baseline. So we'll invite you in to come for a baseline and you would undertake a task. So that might be something like an addition or subtraction task which involves arithmetic, involves planning or working memory so all of these things are quite challenging and cognitively challenging. What we'll do is we'll put them into a brain imager at the same time and then we'll have a comparison. So we'll deprive them of sleep for one, two, maybe up to three days, depending upon the ethics that they get and we'll have a look at how things change. So, how does their performance change cognitively? What's the decline? And what does this seem to correlate with when we think about what's going on in the brain? Basically, they'd work on metabolic principle. So, it's the idea of whenever neurons are active at that time, they need a certain amount of oxygen. These imaging techniques take a look inside the brain and takes advantage of the fact that there are different magnetic properties of oxygenated to de-oxygenated blood. So, while the brain sends blood to the area the neurons are being used and you can see the oxygen that's being kind of taken up by them as a proxy for their activity.

Kat - But what is going on when you're feeling really sleepy?

Laura - Exactly. So looking at these two things, basically, what we see, they're quite congruent with each other. We have global deactivation of the brain but there are certain areas that are really hard hit. And those are.

Kat - So these are bits of the brain that are just going, "Ugh!" just winding down.

Laura - Absolutely and it seems to be dose dependent. So, as the days goes on the decline becomes more progressive. But there were areas that are worst hit at the frontal areas and the thalamus. This really makes sense when we think about our profile earlier because the frontal lobe is responsible for planning our executive function, our memory. The thalamus sits on top of the brainstem and it's really important for alerting. It has all of these feed forward and feedback mechanisms with the frontal lobe. So they talk to each other a lot and it's incredibly important in attention. One more interesting thing is this idea of when we look at sleep. So, when you're in a REM sleep or deep wave sleep, they're the first areas to turn off. So, it tells us that they are very expensive in terms of their oxygen and their glucose use. And they seem to be what benefits most from sleeping.

Kat - So basically, people will make worse decisions when they're tired because these important bits of the brain in decision making are just knackered. Laura - Absolutely. And it's the case and you just have less resources to be able to use and your brain is not functioning. It's not using energy in the correct way, it's not using suction sufficiently, so you are less able to make a good decision.

Kat - Good idea to get a good night's sleep I'm reckoning.

Laura - Absolutely.