Honing in on Headaches

19 June 2020

HEADACHE

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Nearly everyone has had one, with some merely a nuisance and others severely debilitating…. we’re honing in on headaches in this and the next episode of Naked Neuroscience. Plus, we're talking about the latest neuroscience news with our local experts!

In this episode

Brain schematic

01:04 - Can roaming make us happy?

We're delving into the latest Naked neuroscience news!

Can roaming make us happy?
Duncan Astle, Cambridge University; Helen Keyes, ARU

Let's dive into some Naked Neuroscience news, with cognitive neuroscientist Duncan Astle and perceptual psychologist Helen Keyes. First up, as lockdown continues here in the UK, Cambridge University’s Duncan Astle highlighted a perhaps quite pertinent paper about roaming. Duncan told me that the evidence suggests when animals are free to roam in enriched environments, they have greater wellbeing. So can the same be said for us humans? Does being able to go exploring relate to our mood? Well that’s the question the paper he looked at wanted to answer...

Duncan - They took a group of subjects, about 130 of them, and they supplied them with a geo-location tracker. And this tracked their movements around town over a period of three to four months. During that time, they would also send mini surveys to their mobile phones on a regular basis to check up on their mood. After they collected the data, they were able to calculate something called roaming entropy or R.E. It's just a way of providing a measure of how much you move about. And what they found is that subjects' mood was significantly related to their RE. When roaming entropy was higher, their mood was also higher. So on the days where they moved around a lot, they tended to report being in a better mood or having better affect. Secondly, looking across days, they found that mood tended to be highest when those days took in novel locations. And in fact, actually this explains subjects' mood over and above the basic roaming entropy finding. So there's something particularly strong about novelty. And thirdly, what they could do is take into account the socioeconomic diversity of the places that people visited. And they found that when there was a greater diversity of places visited, that was also associated with greater mood.

So two important findings. One is about the novelty. And one is about the diversity of the places that people are going. And both of these things seem to be associated with people's mood.

Katie - Does it make a difference how you move around? Cause I would assume if you're walking around compared to say driving in the car, that would make you feel better. Is the tracker about how you move or just where you're going?

Duncan - I don't think the tracker gives them that level of granularity. I guess it checks your locations on a minute by minute basis. So in theory, they could use that to work out speed.

Katie - OK, but this isn't about exercise, this is about going to different places, regardless of how you get there, right?

Duncan - Yeah exactly so they've controlled for that. One question you might be starting to think is - is it that novelty boosts mood, or is it that when you're in a better mood, you sort of seek out novel places? The answer from their data seems to be that it's both and they can test that by doing what's called a lagged analysis. So for example, they could see whether your mood today is influenced by the novelty of locations from yesterday. Or they could test whether your mood today will influence the novelty of the locations you go to tomorrow. And what they're able to show is that actually all of those relationships were significant. So the lag works in all directions, implying that these things are kind of mutually beneficial to each other. So for instance, when you're starting to feel in a better mood, you seek out more novel places. And in turn seeking out more novel places will have a subsequent beneficial effect on your mood the subsequent day. So you can imagine quite quickly how people can get themselves into positive cycles or negative cycles.

And then finally, half of the subjects went into an MRI scanner. And in particular they were focusing on a part of the brain called the ventral striatum, which is an area that lots of people have implicated in affect and mood. And what they did was to test which areas in the brain are functionally connected with this area, the ventral striatum, in a way that moderates the relationship between someone's roaming behaviour and their mood. And they find there was one particular location, the hippocampus, heavily involved in spatial navigation. So in subjects who have strong coupling between the hippocampus and the ventral striatum, those subjects seem to show a stronger coupling between their roaming behaviors and their mood, implying that there's some kind of neurological basis or neuroscientific basis that mirrors the behavioural relationship between the roaming behaviour and the mood.

Katie - So does that mean for some people, going somewhere else and seeking out a novel environment might be really, really good for your mental wellbeing?

Duncan - Yeah. I can think of lots of different potential explanations. So one is the one that you just said, right? Some people, these areas are just naturally better connected. And as a result, the more mutual benefit, the information can flow more easily between the two. Another account is that this relationship is kind of trained over time. So that the more you do one or the more you kind of co-activate these different brain areas, the more they become functionally coupled. And so what you're seeing in the brain scanner is kind of the after effect of repeatedly co-activating these two different brain areas. But I think it's nice to demonstrate that there is some neuroscientific instantiation of what's obviously happening out there in the real world, in terms of people's experience.

Katie - It feels quite intuitive, that link between seeking novel places and feeling quite good. Does this explain why I really like going on holiday?

Duncan - Ooo, I think there could be lots of reasons why you like going on holiday, depending on what you do when you get there. I think there's lots of ways in which navigation is kind of beneficial for your mood. So I don't know about you, but when I'm trying to find somewhere, it really gets my mind off whatever was going on in the place I just left. And it allows me to somehow mentally sort of draw a line or kind of demarcate what was a particular attentional episode and start a new one. And I can imagine that being able to do that physically in terms of your navigation could have all sorts of mental benefits as well. And I think that whilst we're all currently in lockdown, I suspect that we're not able to do that. And that is one reason why people's moods have been really altered by their experience.

Katie - Helen, do you want to chip in with anything?

Helen - I think it's really interesting in terms of some of the studies we've covered in the last few months around mindfulness and using things like video games to actively take your mind off of a situation, for example off of work stress and how that can really encourage mindfulness and improve your mood and mental wellbeing. It seems to tie in really nicely the idea that both novelty and diversity are improving moods here. Because that is the link isn't it? Novel and diverse places will engage you in a way that is likely to take your mind off your worries, more so than trudging around the same old places again and again. And I think it is probably a significant worry at the moment and that it's not very easy for us to encounter novel or diverse situations. And we probably will see quite a large effect on mood as a result.

 

Anglia Ruskin University's Helen Keyes been delving into confirmation bias this month, which is essentially being more likely to take on board, and, Helen told me, even remember, information that confirms our beliefs. And the paper she’s been looking at seeks to understand this on a neural level. Could the confirmation bias be explained by how the brain likes to take in new information? Well the authors got subjects to do a visual task - to look at moving dots on a screen, decide which way they were moving, and decide how confident they were in that decision. Then, when faced with more moving dots, the scientists wanted to see if people’s degree of confidence in the first dot decision related to how they approached the new information. Helen told me more...

Helen - So the authors of this study recorded 28 participants using MEG, or magnetoencephalography, which records neural activity with really tight timing precision. And participants were shown a series of dots on a screen for about 350 milliseconds. And some of the dots will be moving rightwards or leftwards. And the rest of the dots on the screen will just be moving randomly. Your task is simply to say whether the dots are generally moving rightwards or leftwards. A participant had to indicate their decision. And then importantly, they had to give a rating on their confidence in their decision. Then they received a second sample of dots. The dots were moving in the same way as in the first session. And they were then asked again which direction the dots were moving in and their confidence level.

Because the authors were recording MEG, they were able to look specifically at brain responses, which are known to be involved in evidence accumulation. And they found that if you're a participant and you really felt that these dots were moving in a leftward direction, and you were confident in that, when you saw the next set of dots, your neural activity in these areas that are involved in accumulating evidence was really high, if the evidence agreed with you. So I'll say that again. If the second set of dots agreed with what you believed, agreed with your assertion that these dots were moving in a leftward basis, these parts of your brain that are involved in taking in this information were really active. If the new evidence disconfirmed your decision, so if you thought they were going left, and the second set of dots show that they were going right, those parts of your brain involved in taking in new information, basically just, they just dismiss this information. They were not active.

Really, for relatively unimportant, non-politically motivated decisions, just about dots moving across the screen, people showed a really strong confirmation bias where they tended to favour incorporating new evidence that fit with their initial decision, and ignoring evidence that disconfirmed it. So it shows that this confirmation bias happens, at least in part, at a neural level. And it does suggest that maybe holding a high level of confidence in your decisions makes you more likely to disregard potentially useful information, if it kind of disagrees with your initial decision. This isn't necessarily a negative thing. There's reason to believe this might be to stop us dithering and to enable us to move forward with our decisions.

Katie - See, that's my problem, Helen. I am an ultimate ditherer. I always thought that this was about efficiency. You know, the idea being that the brain only has so much processing power. So why not just use a shortcut? Is that relevant?

Helen - I think it's absolutely relevant. I think it's the brain's way of using your heuristics and saying, "well, you're confident in this decision, I'm just going to direct my resources towards this in an efficient way. And off you go down this path and I'll support you in that". Thank you brain for being very supportive of my decisions.

Katie - Do you think this could open up opportunities to unpick some of the confirmation bias? Is it possible to work on it as a skill, to be less biased in this way?

Helen - It absolutely is. So most of the research prior to this, on the confirmation bias, has been, you know, around this behavioural response. Why is it, for example, that people hold particular political beliefs? Or for example, if somebody is racist or has a very entrenched opinion, there is work done there to show that these entrenched opinions can be challenged and lessened and opinions can be changed. What might be quite interesting is to see when is that happening at the neural level? At what stage is it that we can make that opinion change happen? So how much new evidence or what type of new evidence, or in what new way can we present new evidence that challenges people's deeply held beliefs, that at some stages is going to be absorbed or taken on board in the way we would hope, rather than disregarded.

Katie - Duncan, is there anything you want to add?

Duncan - Yeah, I was gonna ask how confident we are that the mechanisms that govern these dots are the same as other sorts of biases? So let's imagine that there's a really controversial celebrity, and I think they're great and Helen thinks they're awful. I might selectively take on board all the wonderful things that I see in the news. And it kind of reinforces my impression of that person. It might engage all sorts of different kind of emotional processes. How well do you think that kind of confirmation bias translates to, you know, whether the dots are moving left or right on the screen?

Helen - There's more work to be done, but when we take together the huge body of evidence, behaviourally, around what you're describing, we haven't tied that to the neural level. So this is the first type of study looking at whether this confidence effects your decision making and your ability to take onboard new information at a neural level. So yes, the next stage will be to take it back up to that world view level stuff. But what I like about this is we've taken out that motivation altogether in this study. There's no reason why - you know, I might see myself reflected in this particular celebrity and therefore it'd be self-protective to think they were doing a great job. We've removed all that. There's not really these other reasons why people should believe these dots are moving left or right. So we'll work back upwards from there, I think, and do bigger studies on this.

a crack in the earth

Splitting - headaches 101
Amanda Ellison, Durham University

To give us an overview on headaches, Durham University neuroscientist Amanda Ellison has just written a book on exactly this. Amanda told Katie Haylor that headaches allow us a window into better understanding how the brain works in concert with the rest of the body. Firstly, Amanda and Katie discussed some of the different types of headaches that we might come across...

Amanda - There are lots and lots of classifications of headaches. And depending on which classification you look at, you will see that there are headaches and subtypes of headaches and... it's enough to give you a headache! So really what I focused on in this book is five main types of headaches. So we begin our story with brain freeze headache - that, actually more scientifically, is called cold stimulus headache. And lots of us have experienced this, that stabbing pain in your temple when you've gobbled your ice cream too fast, or had a smoothie or something like that. We talk about that and what it is that's going on there.

Then we talk about sinus headache, which is really quite prevalent also, and undervalued, I think, by people, in terms of how pervasive that kind of headache is. It's oftentimes always there. Sinus headache is born out of congestion in your sinuses, hollows in your bones. But sometimes they get very clogged up with mucus and the mucus is there to flush out any bugs or allergens that are in there. Obviously people who deal with allergies every year, they're very used to this, and sometimes these allergies will build up the mucus and then will trap other nasty things like bacteria or viruses inside the sinuses and they find it very, very hard to escape. And so it's inflammation upon inflammation upon inflammation, as your immune response tries to flush out these bugs. And the problem with that then is that your head feels very congested. And it sets off the same kinds of reactions that you get in any other kinds of headaches. You get vasodilation, you get activation of the main pain receptor in the head, which is the trigeminal nerve. All of this is interpreted in your brain as pain, and it actually manifests as a pain in your face and a pain towards the front of your head. So it really feels like you've been hit in the face with a spade.

Katie - Okay. So brain freeze - don't eat your ice cream too fast. Sinus headaches - I think I know the kind of painful pressure build up that you're talking about. Am I on the right lines?

Amanda - Absolutely.

Katie - What are the other three?

Amanda - Tension headache is really, really common. And it's also known as the stress headache, and it is born out of emotional stress, sure, because when we are stressed emotionally, or we've got lots of things going on, you do very much feel stressed and you feel emotionally stressed, but your body actually becomes stressed too. You hold yourself in a different way. Your back is more tense. Your posture is worse. You're possibly rushing around from place to place or exerting energy that you wouldn't ordinarily be exerting. And this will all feed back up to your brain. And if your body feels tense, you feel emotionally tense. Then that doesn't help. Your brain feels like it's under attack. It is very much the fight or flight response.

Originally, it's a very adrenaline based response and that creates the energy in order for us to deal with the problem that we're trying to deal with in front of us. Over the longer term - cortisol, we're talking about a heightened response to stress. This causes generalised inflammation. It also causes an immune response. It causes release of things like nitric oxide that cause vasodilation. And again, now we're getting into the situation where we realise all of these resources come in to the brain to allow us to deal with the problem that's in front of us. It's causing vasodilation of the cerebrovascular system. And that's triggering off the pain receptors in the head, that's says "Danger! Danger! These blood vessels might not be able to take this for much longer".

Katie - Tell me about migraines because I'm certain they're going to be on your list. I think I've had two migraines in my life and honestly, they were absolutely horrendous. I remember feeling sick. I cried a little bit. My head felt like it was going to explode. And the only thing I could do was jump under my bed and try and block out any sensory stimulation until it went away. And if I ever hear someone now saying, "Oh, I think maybe I've had a bit of a migraine the other day", I think, "Did you?" Is that fair?

Amanda - That's entirely fair Katie, yeah. It's terrible. Because when you write a book like this and I've been involved in this field for a long time and it really does make you second guess your fellow man, and woman, because when they do say, "Oh, I had a touch of a migraine. You're like, "no, you don't get a touch of migraine. You either get migraine or you do not." And it's very much along the lines of, "I had a touch of the flu". No, you didn't. You had a cold, it might have been a bad cold, but that was not influenza. And if it was the flu, you would know all about it because flu is an entirely different animal. And it's the same kind of thing with migraine. Not all bad headaches are migraine.

Katie - What is going on that makes a migraine so horrendous?

Amanda - You actually have four stages to it. You have the prodrome phase, which is happening before you even know it's happening. And this is when various things are happening across the cortex of your brain. You're getting waves of excitation, followed by waves of relative inactivity. And this then changes the balance of neurochemicals in your brain. It starts to create a pain-type response. That's all part of the aura phase. Now some people experience an aura, which is a visual or sensory disturbance, and some people do not. But we think now that actually the same thing that's happening in the brain, whether or not you are experiencing the aura. Whether or not you experienced the aura is based on how eloquent your cortex is. So if your cortex is very eloquent, you will experience it as a sensory disturbance. But if it's not very eloquent, well it's happening anyway. And then that then sets up your pain phase. And that's when you get this deep throbbing in parts of your head, usually towards the front, usually on one side, at least initially, and it can be a really horrendous pain. It feels like somebody's just trying to crack your skull open. And you can actually get some really bad sensory disturbances with that as well, because what's happening inside your cortex feeds into your subcortical structures. And they're the things that's do all the things you're not aware of. So breathing, thirst, how hot and cold you feel, your temperature regulation, nausea. All of those different things. And that keeps coming in waves and waves. And that explains how crummy you feel. And it really does knock you flat.

And even after that, then you have the postdrome phase where everything is trying to get back to normal inside your brain. You feel mentally unable to add two and two together because who cares? And you just really have a hard time getting back on your feet. And that's as everything resets. You really do need to just take yourself away to a dark room, and let it all just take its course, unless you take any kind of medication to intervene with migraine. And that really is your body incapacitating you to allow everything to reset to normal.

Katie - In the book, you mentioned cluster headache. And I'm wondering if perhaps this might be number five on your list. You mentioned a man who was out of it for two weeks with a cluster headache! What on Earth is it?

Amanda - Yeah, cluster headache is the strongest headache. It's the one that has been rated as being the worst headache that you can ever get. I've had some experience in witnessing this myself, thankfully, I've never experienced it to my knowledge. I did witness somebody banging their head against the wall with this particular type of headache. It goes back to taking that person out of life and society until what's happening in their brain settles down. And that can take weeks for certain people, particularly if they've missed a particularly small window that they have in order to intervene with this headache.

Now with cluster headache, the name comes from these headaches happening in clusters. So they can happen over the course of a day, or over the course of weeks, or over the course of months. But generally they will be diagnosed if you have five episodes of that separated by remission phases. And they are really, really debilitating. They feel like somebody's trying to force your eye out from the inside. It's horrendous and, and there are various other things that people report, like they have a droopy eye, they're tearing up on one side of their face, it's almost like the paralysed as well. There are lots and lots of different effects of this and people just feel generally awful.

Katie - Is there any way of predicting when this is going to happen? Are there some people who are a bit more sensitive? It just sounds so debilitating. Are there ways of controlling how this comes about?

Amanda - There are absolutely ways of controlling how this comes about. But I think what it requires is a good understanding of A) which type of headache it is that you're prone to. It's very important to identify the kinds of headache that you have. The second thing that you need to do is to think about your body and your life and see how it is that that is impacting on your headache. I say this all the time. With headache, prevention is better than cure, but you've got to understand how you as an individual can prevent the headache for you. We all have different pain thresholds. You actually do have a whole other part of your brain, which we now know is very much involved in our own perception of pain. We also need to then understand where these headaches come from and how that intersects with our lives. Now for tension headaches it's easy to point out "well, you know, you've got posture, you've got dehydration, you've got stress". You've got all of these things that are the umbrella terms that explains it.

But for something like migraine or something like cluster headache, there are things that you can do to make sure that you don't expose yourself to any triggers that are peculiar to you. It's easier in migraine to a degree than with cluster headache, because with cluster headache, we seem to think it has a lot to do with the subcortical regions of our brain and things that are happening automatically. And there are certain things that we cannot control there, like the light that's coming into our eyes and various aspects like that. But with migraine, there's been so many urban myths that have grown up around this. So one of the things I did in the book was try to go through all of that and say, "right, what does it mean from a scientific point of view? What's the literature behind this? What's the evidence behind this?"

Katie - What do you think about the public profile of headaches? Do you think we take them seriously enough? Because a lot of this interview has been pretty heavy going in terms of talking about an awful lot of pain. And sometimes if someone was just to say to me, "I've got a bit of a headache". I probably wouldn't actually take it that seriously.

Amanda - There's an element whereby it isn't taken seriously enough. You have a colleague who says, "I have a bit of a headache" and you say, "well, I've had one for six years and I'm getting on with it". And it's very much dismissed as something that almost you're perceived as being weak if you admit to having a headache. But actually headaches tell us a lot about what's happening inside of our bodies. And we, as individuals, should t take them seriously.

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