Can brain training combat motion sickness?
The paper that cognitive neuroscientist Duncan Astle looked at this month wanted to figure out the relative contributions of REM sleep and non-REM sleep to learning...
Duncan - So they trained people on a visual learning task, and then they let participants have a 90 minute nap. And then when they woke up, they tested them on the task again, to see how much better they'd got from their initial training. Now, whilst they were asleep, they also scanned their brains with a special type of brain scanner called a magnetic resonance spectroscopy scan, or an MRS. And the really neat thing about this scan is it picks up different chemicals in the brain, including neurotransmitters - tiny chemicals that are vital for the communication of electrical signals in everyone's brains. And they looked at two different types of neurotransmitter. So glutamate, which is an excitatory transmitter, it upregulates, or increases, the activity of neurons in the brain. Versus GABA, which is an inhibitory transmitter. It down-regulates or suppresses the activity of different neurons in the brain.
Duncan - So everyone learns a task. Then they go for that nap in the brain scanner and their brains are scanned and, and the relative levels of these different neurotransmitters in the visual areas of their brain that have been responsible for learning the task are measured whilst they sleep. And then they wake up and they're tested on the task again, and they could then establish whether there are any relationships between how good people were at the task when they woke up and what had been happening in their brains as they slept. And what they found was that as people slept, those people who had more non-REM sleep had an excitatory shift in their visual areas. So they got an increase in the glutamate release relative to the GABA. And the bigger that shift, the bigger the improvement on the task that they observed, versus people who had more REM sleep. And they had more of an inhibitory shift in their brain patterns, which seemed to be less well associated with getting better on the task.
Duncan - So there was a twist. So what they then did was they took the same participants and they tried to train them to do a different task, which would interfere with the original task that they had learnt. And so they tried to train them on this different task, and then they test them on the original task to see how much interference they have experienced. And there, they found that the people who did best were those who had had some non-REM sleep, but had also had some of that inhibitory REM sleep. And what they propose is that when you're asleep in that non-REM phase, you get this big increase in excitatory neurotransmitter release that they think might have something to do with brain plasticity. But that what's also important for learning is the stabilisation of those new connections. And so having some REM sleep, the inhibitory shift, they think, has to do with having the stabilisation. And so it's those subjects who have had that bit of stabilisation that showed the best resistance to the interference from the new task.
Katie - I see. So for you to learn something or for your learning to be consolidated when you're asleep, you've got to make those connections. And then you've got to stabilise those connections, and both parts are really important.
Duncan - Yeah, exactly. So people who learnt really well and had loads of non-REM sleep, but had no REM, found that they were highly prone to the interference of the new task, right. So they were able to learn the original task, but as soon as something new comes along, it interferes with their original proficiency on the first task. The best people are those that get a little bit of both.
Katie - So there's quite a lot going on in this study. And I think you said actually earlier, this is just one of four experiments that they did. If you need both REM and non-REM sleep in order to learn something well, what situations would you not get both in a normal night?
Duncan - The timing of the cycles between REM and non-REM sleep are kind of different across different individuals. So for example, in non-REM sleep, there are different stages all the way down to the kind of deepest level of sleep, where the brain is least active. And then gradually the person will rise back up and they'll get to REM sleep, which is like the last step before the person wakes up. Different people cycle through those things at different rates. And so in a night, different people will get different amounts of different levels of sleep. For instance, if I were to wake you up every hour, it might be that you never get to your REM sleep cycle.
Katie - Say if there isn't something specific waking you up, like say, if you've got a young baby or something like that. Say if you have a sleep issue associated with mental ill health, I'm guessing that's going to be pretty important for, as in, a knock on effect for how you learn?
Duncan - Yeah. Actually sleep disturbances is identified in all sorts of different types of disorder, not just adult mental health issues. But for instance, lots of developmental disorders, so kids with ADHD, sleep disturbance is one of the most commonly reported symptoms of having ADHD. And one of the theories going is that one of the reasons why lots of individuals might find it harder to learn, isn't just because of the direct impact of their particular symptoms, like being anxious or being depressed. But it's that combined with having poorer quality sleep, that also contributes to its impact on learning.
Katie - I dunno if this is more of a semantics question, but does it depend on what you're learning? I know this was a visual task, is that right? What if you are doing some sort of, I don't know, just growing up in life, emotional learning or something like that?
Duncan - Yeah. I think that's different. So it may be that sleep's crucial for that in the same way, but we don't know that from these data, but there are other studies. For example, if I teach you new words, like if I taught you the new word cathedruc, to start with you find that people do remember it quite well, but it doesn't interfere with your other known words like cathedral. And so we know that it's not properly represented like a word, but after a good night's sleep, you find that people start to represent it like a real word. And so we know that it will interfere with a real word like cathedral. And so we know that it works for more complex tasks, not just kind of really basic visual learning tasks, even kind of complex vocabulary tasks where you're learning a new word with a new meaning, seem to have sleep dependent learning effects.
Katie - Is it a bit of a perennial issue with sleep science to try and really accurately replicate the sleep that people would have at night at home, normally, in a lab in a 90 minute nap?
Duncan - There are universities that have labs that are specially designed to try and recreate. But I think the reality is that you're never going to perfectly recreate someone's sleep. Because for instance, we are going to have to put some electrodes on their head, to know what sleep stage they're in.
Katie - What would you say the significance of this finding is? Because it certainly makes sense that in order to learn something, you need to have what I would call a good night's sleep, which I guess encompasses multiple sleep cycles and REM and non-REM. Is that novel?
Duncan - I think people have hitherto assumed that the reason that a good night's sleep is important is so that the next day, you're alert and bright-eyed, and that's true probably. But what these data show is that there's another reason, which is actually actually, whilst you're having a good night's sleep, the learning is continuing. As in your brain is continuing in a process of laying down durable representations and durable patterns of activity that will assist you the following day. The more we understand about the neurochemical relationships between what happens when we sleep and how we learn, the better, because there are so many people who have disturbed sleep for various different reasons, like having ADHD. And understanding more about what's going on in the brain when we get good sleep, might in the long run, actually help us intervene and support those people who could do with a better night's sleep.
Perceptual psychologist Helen Keyes mused over motion sickness this month...
Helen - One in three of us suffer quite significantly from motion sickness when we're travelling. And aside from medications, there are actually very few ways to alleviate this. But there is some research that shows that habituation or repeated exposure to travel sickness inducing situations can help to alleviate the problem. Now, as you can imagine, repeatedly exposing yourself to being travel sick is not a pleasant solution to the problem.
Katie - Urgh, no. Repeatedly exposing myself to motion sickness does not sound like my cup of tea! Helen explained that motion sickness arises out of a disconnect between what you're seeing and what your body is feeling.
Helen - Some research had previously noted an interesting link between visuo-spatial abilities and travel sickness. They noted that people who have greater visuo-spatial control abilities are less susceptible to travel sickness. Visuo-spatial abilities, essentially just how you are at moving through the world. So mentally rotating scenes in your head, how you are at hand-eye coordination, all of these things are tied in together. So just your spatial awareness and your control of that. And so that had been what previous research had shown us, but there's very little done on this. But it did lead the researchers to ask whether people could be trained to have better visuo-spatial skills. And if so, whether this in turn would lead to reduced travel sickness.
Helen - So they tested just that, they had 42 participants, which is very few, and that was further divided down so that 20 of those participants did their testing in a driving simulator. Driving simulators are really famous for their travel sickness effects. So they're a pretty good tool to use for this study. Then the other 22 participants were in a real car being driven around on the road. Now those other 22 participants, only 15 of them were in the real experimental condition. And the other seven were in a control condition.
Helen - So what did they do? Well before anybody began any of their testing, a measure of visuo-spatial skills were taken, and this was done using the classic mental rotation task. You may have come across this, you're shown an image of some blocks in a particular configuration, and you are asked to rotate that mentally in your head, and then you have to choose which one it would match up with if it were rotated. So it's a good measure of your visuo-spatial skills.
Katie - Oh dear. I find that sort of thing really hard. I have to turn the Ikea flat pack instruction guide to the way that the stuff is sitting in my living room.
Helen - And do you also suffer from travel sickness?
Katie - Yes!
Helen - Well, there you go. You've just demonstrated what these researchers were looking for! They wanted to have a kind of baseline measure of people's motion sickness. So initially, participants would either be in the driving simulator or be driven around in the car for 30 minutes, and then they would have a measure of their driving or motion sickness taken. Then for 14 days, once a day, participants would use a visuo-spatial training pack, pen and paper tasks, like looking at an unfolded cube and trying to manipulate that in their heads to think what it would look like as a folded cube, those types of tasks. And then after the 14 days, they would repeat the driving task. So they would either go back into the driving simulator, or they would again be driven around in a car. And again, their motion sickness measures would be taken. And they would also do the mental rotation task again to see if their abilities had improved.
Helen - So the first finding was that people who took part in the training did show a significant improvement in the mental rotation task. Following this training, motion sickness scores reduced hugely - by 51% in the simulator group and by 58% in the on-road group. Whereas for the controls, the people who didn't do any training at all, motion sickness scores didn't change. So the visuo-spatial training did seem to reduce levels of travel sickness quite significantly.
Helen - The authors are really keen to point out the benefits of this type of brain for travel in automated vehicles. So we are predicting that as driving becomes more and more automated, even drivers may eventually be able to engage in reading or watching screens or even producing work while they're driving. And in this way, they're saying, well, perhaps this training could reduce the ill effects of motion sickness. I would say though, that it is a very small sample size and to make these claims on, but there were huge effects. So that does give us some hope.
Helen - Essentially, what the authors think is happening is that the visuo-spatial training is leading to an enhanced ability to resolve visuo-spatial conflicts. And that's essentially what travel sickness is. It's a conflict between your visual information and the spatial and bodily information that you're feeling. So they think just practicing, manipulating those and controlling those visual spatial tasks is helping you to resolve those conflicts when you're in the car.
Katie - Does this particular study help establish that kind of crux, that mechanism, of what's actually changing in someone who has that problem compared to people who don't?
Helen - I think it does. Because we know from previous research that, you know, you can essentially get into a habit of, if you put yourself in the situation of being traveled sick a lot of times, it can help to reduce that effect. We're thinking it's tapping into the same thing, your body is getting practice at resolving those conflicts, those visup-spatial conflicts. And that seems to be just essentially getting you used to it, and you don't feel so ill with it.
Katie - And why is it that if I'm actually driving in a car, I'm in control of the vehicle, I don't get travel sick. But if I'm a passenger, every time I get travel sick! What's going on there?
Helen - I think that's a really interesting question, and it's a really universal effect. Drivers have less motion sickness than passengers. Obviously you're not in control of the motion. So if you're ever doing any virtual reality headsets or you're ever really immersed, like in the driving simulator, where movement is happening, even if your body and eyes are moving, movement is happening, but you're not in control of it, or you don't feel like it's part of what your body is doing, that's more of a conflict for you. It's less predictable for you. But secondly, when you're a passenger, you're also less likely to have your eyes directly on the horizon, on the moving outside of the car. You're more likely, again, to be focusing on other parts, perhaps looking at your phone, things like that. So there's two reasons, but the main reason is your body isn't in control of that motion that's happening to it.
Katie - Helen, as you said, this is quite a small number of people involved in this study. How convinced are you of the strength of this association?
Helen - Not that convinced Katie because the sample is so small, you know, it would be a really magnificent and strong effect if it was this simple to resolve motion sickness. This is wonderful. On the basis of this study, I am going to give it a try myself, I have to say, if I'm going to be doing something where I'm going to be a passenger on a long journey. But it is such a small sample size to make these claims on. The size of the effects, reducing motion sickness by 51 or 58%, that's huge. So that does suggest there's something there, that it's not just some sort of minor fluke, but really there's no other literature on this and people haven't done work on this. It's kind of a lone ranger, a bit of a Wild West here with this new exciting study, and I think it's going to need a lot more work before we can be confident that it's a real effect.
Katie - Duncan?
Duncan - I just wanted to ask about the control condition?
Helen - The control condition was not very well run. So there were only seven people in the control condition and they were only in the car driving condition. They didn't do a control for the driving simulator. And the control condition didn't involve any sort of real control. It involves the people doing nothing for the 14 days and then coming back and being tested again. Whereas obviously a better control would have involved them engaging in some sort of other pen and paper task everyday for 15 minutes. It could well be a placebo effect. We need to bear in mind that these motion sickness measures were self-reported motion sickness. It's very possible you would want to be pleasing the researcher and give lower scores there in the direction you thought the researcher wanted. This is not the most methodologically sound study I've ever come across, but the effects were just so large that this really lept out at me as something that was quite interesting and perhaps worthy of further investigation.