Decision-making and adaptive control over impulsive actions
by Dagmar van der Neut
Impulsivity and decision-making, those are the main themes of an ambitious research project that will be conducted within the university research priority program Brain & Cognition and that stretches across research groups from different faculties at the University of Amsterdam and beyond. Philosophy, biology, economics, psychiatry, genetics, electrophysiology, neuropharmacology, mathematics and psychology-all those disciplines come together in one large research project: Decision-making and adaptive control over impulsive actions. The goal: to understand the neurocognitive mechanisms behind decision-making, and particularly those behind impulsive decisions and actions.
Richard Ridderinkhof, Eric-Jan Wagenmakers and Birte Forstmann are the lead researchers in the Faculty of Psychology. Together with Frans van Winden, professor of economics, and Damiaan Denys, professor of psychiatry at the AMC, they supervise postdocs and graduate students who will conduct seven different research projects.
This interdisciplinarity has added value, says professor of developmental psychology Richard Ridderinkhof. ‘In all those disciplines, we've already been working on specific research questions for some time. But what is sometimes lacking are a number of approaches or handles that would enable us to study decision-making and impulsivity in all its richness.'
Economists, for instance, will approach psychologists and neuroscientists for collaboration, says professor of economics Frans van Winden. ‘Economic decisions turn out to be influenced by various social, affective and cognitive processes. Out of these collaborations new disciplines arise, such as neuroeconomics.'
The collaboration between disciplines and the elimination of boundaries between them also fits with a shift in opinion about psychic disorders. Ridderinkhof: ‘In the past, we thought in terms of separate disorders. Now we're starting to think in terms of dimensions and concepts that go across disorders. Impulsivity is such a dimension. You see disruptions of it in Parkinson's Disease, ADHD, Obsessive Compulsive Disorder, addiction, eating disorders and aging.'
In the brain, it appears that it's mostly the frontostriatal circuit that regulates impulsivity and control over impulses. That circuit consists of the striatum-a structure situated somewhat deeper in the frontal lobe-and the prefrontal cortex. Ridderinkhof: ‘While driving, most actions are done on automatic pilot. The striatum plays an important role in this. But when you approach a roundabout, sometimes some actions have to be temporarily stopped until it's clear what you have to do. Do you have the right of way, or not? Which exit should you take? Which lane should you get into? Should you downshift? Order is required for those actions. The frontal cortex then joins in to adjust the automatic actions and set priorities.'
In impulse control disorders, it is possible that the striatum responds too quickly to a first impulse, or that the frontal cortex cannot sufficiently adjust. For patient treatment, it is crucial to know what exactly happens in the brain. Because where should you intervene?
In serious cases of Parkinson's and OCD, physicians are already using Deep Brain Stimulation (DBS). This involves, for example, intervening in the striatum, which is suspected to be hyperactive in OCD. An electrode planted in the brain core then has to reduce or shut down that activity. The function of the frontal cortex-the top-down control-can also be addressed through cognitive training, for instance. In years to come, this training will also be studied as part of this project.
Ridderinkhof: ‘You can practice flexibility, for example-not panicking when the speed of a task is being increased. But the working memory-important for top-down control of fundamental processes-or the suppressing of impulses can also be trained. For people with impulsivity problems this may be difficult, but not impossible. Brain training has been successful, for example in children with a mild cognitive impairment.'
To better map out cognitive and neural processes, Ridderinkhof wants to study choice processes in their most fundamental form. He and his colleagues do this by using the moving dots task, among others. In this task, a subject has to choose in which direction the most dots are moving across a computer screen. Sometimes that's easy (80 percent of the dots moves toward the right), but sometimes there is a lot of "noise" (60 percent moves toward the right, 40 percent moves randomly).
This task is a simplistic representation of the bombardment of visual stimuli that is launched at us in real life. How do we choose what is important to us in our environment? What draws our attention? How important are our intentions in what we perceive? Eventually it could turn out that someone who makes impulsive decisions too often will respond differently to such moving dots than a healthy subject.
Ridderinkhof: ‘When you're impulsive, you may go for the first source of information you see. Or for the strongest, and you're not capable of "parking" that information until you've absorbed all the input. When you're waiting for a traffic light and the traffic light next to you turns green, you sometimes have a tendency start driving, too. One person suppresses this with more difficulty than another. In disorders such a dominant stimulus can be very specific-to a germaphobe (someone obsessed with cleanliness), a "dirty" door knob will be the only thing he or she pays attention to.'
The outcomes of these fundamental experiments are analyzed with mathematical models. Mathematical psychologist Eric-Jan Wagenmakers and cognitive neuroscientist Birte Forstmann play an important role in this. Wagenmakers: ‘From those fundamental decision experiments, such as the dot task, you get a lot of data that is difficult to interpret. If someone is slow at deciding, for instance, you don't yet know if that's because he or she is not that good at performing the task or is being cautious and doesn't want to make mistakes. A mathematical model can clarify for each individual how cautious that person is, for example.'
‘Once we've used the model to reduce the complex behavior of people down to easily interpretable psychological processes, we can link those to brain imaging data. With this type of analysis, we can identify very precisely the brain areas that are involved in psychological processes such as cautiousness.'
Neuroscientist Birte Forstmann can make visible the brain cores and neural networks involved in decisions in every individual subject. Forstmann: ‘Using ultrahigh-resolution scanners, a fairly new technique, we can zoom in on very specific brain areas that are deep inside the brain and very small. And diffusion weighted imaging makes visible the white matter tracks, the highways of the brain. We have preliminary evidence that there is not only a difference in brain activity between cautious and fast decision makers, but that the brain structures are different, too.'
Although there will be a lot of focus on studying the fundamental underlying processes present in every human, Ridderinkhof also wants to study individual differences. This, too, is a new trend in the cognitive neurosciences.
Ridderinkhof: ‘In the past, these individual differences within certain groups-such as the elderly-were seen as noise. But now we actually use those differences to get a better view of the nature of underlying processes. When you look at cognitive flexibility, elderly people turn out to be less flexible than young people, on average. But elderly people differ more from each other than younger people do! A 90-year-old is sometimes as flexible as an average forty-year-old, and there are young people who are as rigid as the average senior. We simply cannot talk about the elderly person.'
It is interesting to find out what causes these differences, says Ridderinkhof. ‘Because not every addict responds equally well to a particular treatment, for example. We know far too little about this. That's why this project is so important.'
Also new in this project is the use of combinations of different measurement techniques, such as fMRI, EEG, TMS and DBS. In the past, these techniques were predominantly used by themselves. But now, for example, an EEG will also be recorded while a Transcranial Magnetic Stimulation (TMS) treatment is being performed. That shows the direct effect of the stimulation on the brain. It also allows-much more clearly than before- mapping when and how different brain areas communicate with each other.
The collaboration between the different disciplines also facilitates research that would not have been possible within the researchers' own faculty. For example, in collaboration with the AMC and the Faculty of Economy a study is now running that examines the taking of financially risky decisions. Patients with a severe form of compulsive disorder, depression and addiction are being treated with Deep Brain Stimulation (DBS) at the AMC.
Damiaan Denys, professor of psychiatry at the AMC: ‘In these patients, two electrodes are planted deep inside the brain's reward center. These allow us to correct the activity in the brain circuits. But you can also connect the electrodes to EEG equipment and use them to conduct measurements. The patient can then perform cognitive decision tasks, and we can simultaneously see what exactly happens in the brain. In this way, we obtain very special information, such as how the brain responds to reward and punishment or what happens in the reward center when someone takes risky decisions. It is the first time that this is being studied in this way. That happens nowhere else in the world.'
These types of experiments will certainly result in joint publications in years to come. Ridderinkhof especially hopes that the project will lead to progressive insight. ‘I don't have the illusion that in a few years we'll know everything exactly. But given the multidisciplinary and multimodal approach I expect that we'll be able to make considerably large strides.
Prof. dr. Richard Ridderinkhof (Psychology)
Prof. dr. Frans van Winden (CREED)
Prof. dr. Damiaan Denys (AMC)
Dr. Birte Forstmann (Psychology)
Dr. Eric-Jan Wagenmakers (Psychology)
The following institutes participate: