How much of a risk taker are you?

20 September 2019

Interview with 

Helen Keyes, ARU; Duncan Astle, Cambridge University

BRAIN

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Joining Katie Haylor to check out the latest neuroscience news stories are psychologist Helen Keyes and neuroscientist Duncan Astle. First up, Helen talked about a paper looking at how the degree to which we take risks may fluctuate more than we think...

Helen - I've been looking at a paper asking why it is that sometimes we make risky decisions whereas sometimes we might be more risk averse. And this study suggests that perhaps we're not quite as stable as we might think we are. And while it might be true that we might have some risk taking traits or some risk averse traits, this study does show that actually our behaviour is quite erratic, more erratic than we might like to believe about ourselves.

So the background of this is we tend to look at risk taking at a population level, and that some people are prone to taking risks. In particular younger people are known to be more prone to taking risks than older people by about 5 percent. This study is run on the basis that we are almost slaves to the brain chemical dopamine so dopamine - a feel good chemical in your brain. And generally people whose brains are saturated with dopamine will take more risks. This is really widely established and in general a big head of dopamine feels good and people can tend to return for another rush, it can lead to a lot of addictive behaviours.

In this study the researchers used fMRI which can show us different levels of activity in the brain over a period of time and they focused on the dopaminurgic midbrain. This is part of your brain that's really centrally involved in decision making. What was really neat about this study was that they tied the presentation of stimulus to your brain responses. So they looked at the dopaminurgic midbrain and if you were just in your resting state, had very low activity there, this would trigger the presentation of a stimulus.

Katie -  And the stimulus is doing something risky?

Helen - It is indeed. So the interesting part is they tied the presentation of a stimulus to when you in your resting state had low or high activity in this region. And when that happened, let's say you had low resting activity in this region, you would then be presented with an interesting potentially risky choice.

So you would be asked to choose on a gambling task as to whether you wanted to go for a low amount of money, a safe option so say three pounds, or whether you wanted to make a choice, a gamble, where you could get more money than that so potentially six or nine pounds or zero.

And they found that if in your dopaminurgic midbrain you had very low activity, a low resting state, and you're suddenly presented with this gambling choice, there's quite a spike in your dopamine activity. And that spike in dopamine leads to you actually taking a more risky decision. So within the same session, if in your resting state you had a high activity in this brain area and you're presented with a risky choice, there wasn't quite the same dopamine spike and you tended to make a safer choice.

Katie - Ah OK. But this is within one person, right? So does that mean on any given day you can have higher or lower levels of dopamine in your brain?

Helen - It absolutely does and this is what was quite surprising about this study. It was really neat just within one fMRI session people were making quite different gambling choices, just on things we have no control over, so background fluctuations in resting state activity in this part of your brain.

Katie - Here’s me thinking that I'm a very habitually cautious person, maybe that is not true?

Helen - Well you may be a habitually cautious person, but I think you might not be as consistent within yourself as you might think. We need to remember that risk taking activity isn't just a generic negative. There can be real reasons for us taking risks! So if we want to be ambitious and make progress, whether that's in our work life, or our romantic life, or any aspect of our life, we're gonna need to have these fluctuations, we're gonna need to sometimes push ourselves and take a few more risks.

And this mechanism might be quite helpful for this and indeed the authors of this study suggest these background fluctuations might make us a bit more unpredictable and even might make us better able to adapt to different situations. So there could be good use in these background fluctuations.

I think what this does point to is we can be a bit more self-aware. So it does suggest that some decisions we're making or the way you make decisions can be somewhat out of our control, our behaviour can be somewhat erratic. It doesn't give us much hope, does it, for ourselves!

But what it does suggest is that things that I'm quite interested in, like the development of driverless cars, could be really really good because if these background fluctuations are going to affect particularly risk taking behaviour, let's take that out of the equation altogether and make more sensible choices.

Duncan - It’s interesting that there are various conditions where risk taking can become pathological. So for instance people who become addicted to dangerous narcotics and that kind of thing. And there's been a lot of interest in the role that the dopamine system plays. Are there underlying genetic differences in our dopamine systems, such that for instance if some people's dopamine systems are just much more erratic, then that means that there might be periods where they're exceptionally prone to taking big risks like, “inject this substance”?

Katie - Oh I see. So there's fluctuation in everyone but there could be more fluctuation in some people.

Duncan - Yeah. So there is some genetic susceptibility for certain types of substance abuse addiction for example. And it's interesting that there are various medications on the market to try and mimic dopamine action so for instance something like Parkinson's where because of the loss of dopamine receptors, the medication tries to boost the amount of dopamine.

And what you'd find is exactly what you'd expect from what you've said is that, that obviously helps with some symptoms, but they start to struggle with any tasks that require them to gauge rewards and make choices about rewards i.e. make risks. Because their levels of dopamine are just high the whole time

Duncan looked at a stimulating paper on transcranial magnetic stimulation...

Duncan - So this is using transcranial magnetic stimulation. It's also very interesting paper and it's looking at anhedonia, inability to find joy and enjoyment in the things that we do.

Katie -  Are you talking about depression?

Duncan -  It is a very common symptom. About 70 percent of those with major depressive disorder will experience this symptom. It's regarded as a very stubborn symptom for treatment options and people who score particularly highly on this symptom tend to be those who are most resistant to the current forms of treatment.

So in this study they recruited 19 subjects who all had major depressive disorder and particular problems with anhedonia. They rated them on an anhedonia scale. And they also performed a task which required them to look at faces that convey different types of emotion, and those faces are manipulated to make it really tricky to judge the differences, e.g. how happy is this person?

Then the subjects are divided into two groups and both of them receive a type of stimulation applied to a part of the frontal lobe called the dorsal lateral prefrontal cortex, which people have previously thought might be important in the symptom of anhedonia.

Katie - What does it mean to stimulate this bit of the brain? What are you doing to somebody?

Duncan - So you will remember from GCSE or equivalent physics that wherever you get an electrical current running in a particular direction you will also get a magnetic field running counter to it. It’s called the right hand rule.

Katie - This does bring back memories of my physics lessons!

Duncan - The same is true of your brain. So when the neurons fire, the axons in different layers of the brain are really well aligned and that can create an electrical current that generates magnetic field, and we can measure that outside the brain. And the same thing goes in reverse if we can induce a big magnetic field just outside your head, then we can kind of fire the electrical activity within those neurons.

And so what TMS does, it's two coils, essentially a big loop of iron that has got lots of wire wrapped around it. And then at the flick of a switch a very large electrical current is put through the wire to create an electromagnet. And then when that's applied to the outside of your head, it generates a big enough magnetic field on the outside to get the neurons firing on the inside.

Katie - So how does this relate to anhedonia then?

Duncan - Good question. So what they did essentially was to apply repetitive transcranial magnetic stimulation to this part of the brain called the dorsal lateral prefrontal cortex. And they did it for 20 sessions and in each session a person would receive 3000 bursts of TMS and this at 10 hertz at 10 per second.

And then people come back into the lab, they repeat the emotional faces task, and they repeat the anhedonia questionnaire. Now half of the group unbeknownst to them they are not receiving the real stimulation. And what they find is that people who have had the real deal active stimulation do indeed show better sensitivity on that faces task, and the degree of change on the faces task is predictive of the degree of improvement that they show on the anhedonia questionnaire.

Katie - So what's going on to make this relationship?

Duncan - Well one popular idea is that there are various parts of the brain which are something called the limbic system so areas like the amygdala, that are really important in processing emotional content. But that that can be regulated by other areas like the dorsal lateral prefrontal cortex.

And what might be going wrong in subjects who experience anhedonia, is they’re not able to regulate this lower level brain area. And so one possibility is that by stimulating the dorsal lateral prefrontal cortex it’s then better able to regulate the amygdala and thus you're better able to experience the emotional content of the faces and experience less anhedonia.

This kind of thing is seen as a potential alternative route to treatment. So we know that the current best quality NHS gold standard treatment, which is usually cognitive behavioural therapy with some kind of pharmaceutical agent, is effective fir 50 to 60 per cent of individuals. And so treatments like this are seen as a possibility.

But there are some real questions surrounding it. Number one its feasibility, so can we really scale this up? Secondly how long does it last? Would the person keep having to come back in every couple of months for another set of sessions? Can you deliver it to people of all ages? Could you give this to an adolescent for example who is particularly prone to depression?

Katie - Do we know anything about what happens to the brain of a younger person who you're putting in this situation?

Duncan - Not really. There've been some long term follow up to this kind of stimulation done with adults, but there's not really been any work done with kids because we don't really know the effect that it might have on the developing brain.

Katie - I'm assuming that this is a safe technology that doesn't seem to cause brain regions any harm?

Duncan - Yeah so there's no evidence whatsoever that this does any harm to the brain.

These studies are relatively high risk to run so they tend to be run on a small scale. So really to see whether it's genuinely effective you'd need to scale it up.

Katie - Do you think looking at people's faces, where the emotion is difficult to read, is a good measure of anhedonia? It sounds like something that could be quite a difficult task even if you don't have anhedonia.

Duncan - There might be lots of reasons why you might be bad at that task. A general challenge is finding tasks that sit between the kind of basic intervention you've done, whether it be a drug, a therapy, stimulation technique, and the ultimate outcome which is symptoms in the real world. So in the middle of that we try and think of tasks that we think might be sensitive to the underlying symptoms. But ultimately they're always quite a long way from the real world. Sitting in a lab and looking at faces static on the screen as they flash up in 2D isn't really much like real life but at the minute it's kind of the closest that we can get in the lab setting.

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