Science Interviews

Interview

Fri, 6th Jun 2014

How sleep helps you learn

Peter Oliver, Oxford University

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Could sleep help you boost your learning power? Sleeping Student

We've all heard the phrase "sleep on it", and there are many anecdotes from people such as students and musicians who find that getting a good night's sleep after studying or practising helps with learning.

But what's going on in the brain? Its secrets are now revealed in research from scientists in America and China, showing that nerve cells, or neurons, in the brains of mice grow new connections as they sleep that help them learn.

Kat Arney caught up with sleep scientist Peter Oliver from Oxford University, who started by explaining what's going on in our brains as we visit the land of Nod.

Peter -   The brain is very active when weíre asleep and thatís really the first point.  So, when weíre asleep, itís not like the brain is switched off.  Itís firing all the time, making new contacts.  And these new contacts the brain makes during the night and how the cells connect to one another, thatís often called memory consolidation.  The idea is that when weíre asleep, the brain is active.  If you like, itís replaying events that have happened during the day and this will help us remember things for the future Ė both the next day and also for longer term.  The case is memory consolidation.  So, this is a fairly new topic and a slightly controversial topic.  The evidence for memory consolidation is quite new in the field and relies on very complex experiments, but certainly true.  There's lots of evidence that sleep is a very active process.  Sleep is really important for our brains and has a very useful function.  These new connections made when weíre asleep are really important for us.  Thatís really the background behind it.

Kat -   So, what have the researchers done in this paper?

Peter -   So, what theyíve done is they try to understand more a bit about the structural elements in the brain that they change when somebody has carried out as task.  This is actually using mice.  So, the mice have been trained on a simple Ė what's called a motor task with simple movement task.  They were taught to walk on a rotating rod.  Itís a bit like a toilet roll holder connected to a motor and then it rotates slowly.  This allows the mice to walk along Ė very simple, very simple task.  But also, as they're doing the task, the brain is having to learn the task and make new connections.  They showed that the brain was actually changing its structures, very subtle changes in a very small group of new cells in the brain.  So, neurons in the brain were changing.  And then what they did is they let the mice have a normal night sleep and they see what happens the next day after a normal night sleep.  What they found is that these particular structural changes were still there after they'd had a normal night sleep.  So the fact that the neurons had been firing when they're asleep was promoting these new, very small and subtle but important structural changes in these neurons.

Kat -   So, these are like little fingers that help the nerve cells talk to each other.

Peter -   Exactly right.  So, itís actually crucial.  So, as you know, the brain is very, very complex.  There's probably a hundred billion neurons in a human brain and itís incredibly interconnected.  So, many neurons are interconnected to many, many others.  Itís a bit like you're standing in a large crowd and you decided to hold hands with the person next to you.  You have to put your hand out first to do that and then that person will put their hand out and then you'll hold hands.  And then you might do that to someone else.  So, this is the way the connections are made in the brain.  So, if you like, there's a big crowd of people all holding hands in different combinations to allow people to communicate.  Thatís really what happens in the brain.  So, the important thing in these studies that they show that having a normal night sleep actually promotes these new connections in the brain.  And these new structures, these new connections are maintained for several days later.  Thatís really the key thing.  I think why this is important is because itís now shown in real detail how flexible and how new structure changes occur during sleep and how that can affect memory in the future.

Kat -   How do they know it was definitely sleep that was doing this?

Peter -   So, what they did under control for sleep is they actually carried out some sleep deprivation experiments.  Itís where they will actually make sure that the mice donít sleep.  Normally, they're keeping awake and they carried out experiments in parallel.  What they showed, that there was actually a reduction in the amount of this spine formation or reduction in the structural changes in the brain when the mice had had disturbed sleep.  So, there's definitely a strong link then between the quality of sleep, the type of sleep that these mice were getting and also, the amount of these increase in these dendritic spines that are occurring overnight.  So, there's definitely a strong link between the type of sleep, the quality of sleep, and also, the structural changes in the brain.  So the idea is, the better sleep you have, the longer sleep you have, and the more sleep you have in whatís called the deep sleep or slow wave sleep, this is more likely to allow new connections in the brain to occur.

Kat -   Now obviously, when a story like this hits the headlines, people are like, ďIs this relevant to humans?Ē  These studies have been done in mice.  Do you think they are going to be relevant to humans?

Peter -   Yes, certainly.  What we know about the firing of the brain during sleep is very similar in most mammals.  The structures of the brain we looked at in this particular study are very similar to those found in humans.  So, there's a direct correlation between the structures that are being examined.  Certainly, a rodentís sleep is very similar to a humanís sleep in terms of the type of sleep they get.  The different phase of sleep are very similar, so although mice are nocturnal compared to humans mostly being living during the daytime that their data has lots of direct parallels with humans.  Certainly, we know from lots of work that having good night sleep is very important for humans, both for their physical health and also for their mental health, and for their formation of new memories.  So certainly, this has direct and very important implications for humans Ė both in disease situations, but also in just normal daily lives.

Kat -   So for example, I'm a musician.  So, if I was trying to learn a piece, I should do some practice and then sleep on it and do a bit more in that and that would be better than just kind of keeping going on it.

Peter -   I think thatís kind of what this ton of work is pointing towards.  I think there's a long way to go to really correlate directly between a physical activity one day, a good night sleep and improving your performance the next day on very complex tasks.  But certainly, this data shows a very simple task can actually be related directly to changes of the brain which might help you remember things in the future.  Certainly, with the world cup coming up, if the England team are practicing penalties every day as apparently they are as I heard from Steven Gerard today, and then they sleep really well and practice the next day and then sleep really well the next day, it doesnít really guarantee theyíll score when against Italy or one of the other teams in the future.  But certainly, I hope the team is sleeping well this week.

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Did anyone catch the primary reference for this podcast? I'd like to read the original paper. Teri, Mon, 3rd Aug 2015

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