Category Archives: wetenschapsnieuws

Spinoza laureate Eveline Crone studies how temperament influences prosocial development

On September 12th professor Eveline Crone will receive the Spinozapremie – a grant of 2,5 million euro. What questions will she try to answer with the funds?

Receiving such a large sum of money – not designated for a specific research proposal, but to be spent on whatever line of research the laureate considers most important, does not happen everyday. ‘It is a great honor,’ the professor of neurocognitive developmental psychology reflects on her situation. ‘There are so many things I would like to study and now I get the opportunity to actually execute some of my ideas, but it is also quite overwhelming. Where to start?!’

She decided to choose two lines of research. One to enrich the longitudinal study she already set up – to gain a better understanding of the role temperament plays in determining the developmental path an adolescent embarks on. The other is a leap in unchartered territories – studying the brain activation patterns of entire families to figure out how prosocial behavior develops in the family context.

Temperament
In the first research line the grant will allow Crone and her colleagues to measure the hormone levels and mood states of their participants over the course of a week, rather than performing just one measurement during the participant’s visit to the lab. ‘That way, we don’t only obtain a baseline measure but we’ll be able to see the responsiveness of emotional states and hormone levels during the activities of daily life – a valuable and reliable indication of temperament.’ This means Crone and her team can analyse how temperament might play a role in the establishment of a self image, for example.

‘Furthermore, we know puberty is a differentiating period for prosocial behavior or the care and consideration for others,’ Crone continues. Before puberty, kids are stable and generally prosocial. Post-puberty adolescents are also stable, but the extent to which they consider others vastly differs from one individual to the next. ‘I suspect that gaining better insight into temperament and into the interactions between temperament and environment, will help us understand how prosocial developmental takes shape.’

Synchronicity
The other part of Crone’s research project also focuses on prosocial behavior, but here the emphasis is on the family context of the child. She plans to set up an experiment where neural activity of both the child and the parents and possible siblings is measured, while they play a game where they are involved in prosocial behavior, like donating money to each other. ‘I am curious to see to what extent neural activation patterns are similar between family members. And whether this synchronicity is influenced by the level of harmony within the family. Intuitively we might expect family harmony to determine synchronicity, but this type of neural activation study in a family context has never been done. Nor do we have other empirical evidence that this relationship exists so it really is an uncertain project. But I think I should consider the Spinoza grant as an encouragement to follow my intuition and take the risk to start an ambitious project that could really teach us something new.’

 

Text: Marieke Buijs

Wanted: the brain’s timekeeper

How does the human brain keep track of time? The question fascinates professor Hedderik van Rijn: ‘Timing is crucial in many aspects of human behavior, also in higher cognitive processes. In order to understand those, we need to understand how timing works.’ A Vici grant helps him track down the temporal workings of the brain.

You ring your neighbor’s doorbell and at a certain moment decide to turn away because she’s not home. You’re in a conversation and know exactly when to nod or pause or pose the next question. Or – in a more dramatic situation – a police officer commands a suspect to put away his weapon and at a certain moment decides to pull his trigger. How do we keep track of time in these kinds of situations? We don’t look at our watch to tell us how long we have been waiting at the door, some internal mechanism helps us determine when it’s time to take the next step in what we are doing.

Fundamentally mistaken
For decades, scientists speculated this temporal behavior is managed by an internal clock, a kind of stopwatch that starts running when we ring the doorbell and gives a signal when the appropriate ‘waiting at the door time’ has passed. But despite many efforts, researchers have not been able to identify any traces of this neural stopwatch. This lead Van Rijn to suspect our conception of how the brain keeps track of time is fundamentally mistaken.

‘The information associated with the actions we’re involved in is temporarily stored by oscillations in our working memory. Why would we assume that besides these oscillations, there would be a separate brain mechanism involved in tracking the temporal aspects of the things we do?’ Van Rijn asks. ‘That does not seem efficient to me.’

His idea; the decay in working memory oscillations that occurs over time, could function as a time stamp for the items represented. And the striatal region known to be involved in action selection, the basal ganglia, have specific cells that read the changes in working memory oscillations and signal timing information about those oscillations.

Rushed decisions
That theory would also explain our ability to keep track of the multitude of different things we might be doing simultaneously, Van Rijn argues. Whiles driving for example, we keep track of the timing of speech in a conversation with our passenger, we check our mirrors and speed indicator with a certain frequency and meanwhile we also regularly check-in with the toddler snoozing in the back seat. ‘Rather than having separate stopwatches running for all these actions, the time sensitive cells in the basal ganglia could keep track of all of them.’

The Vici grant allows Van Rijn and his research group to test this theory in different ways. For example, they will use a high definition fMRI scanner in an attempt to pinpoint the striatal cells that correspond to different time stamps. Van Rijn explains that this is the riskiest part of the study, which he can only afford to undertake because the grant allows him enough time to also cover other research paths. ‘It is a bit of a leap of faith because we really don’t know whether the measurement will be sensitive enough to distinguish the cells we expect to be involved in timing.’

In another research line, Van Rijn tries to unravel how external factors like heat and internal factors like emotions can influence the perception of time. ‘We experience time to go relatively fast when we are emotional. Could that be caused by faster decay in the working memory oscillations? Insight into that question might also help us find ways to teach people to not make rushed decisions, the relevance of which becomes crystal clear when we think about the example of a police officer deciding to pull the trigger.’

 

Text: Marieke Buijs

How do our expectations shape perception?

Only through their senses do humans and other organisms have access to the information in the world surrounding them. In the processing of this sensory information, factors like our expectations and previous experiences come into play. Heleen Slagter, associate professor at the University of Amsterdam, tries to unravel the neural mechanisms involved in the interplay between our expectations and perception. The European Research Council supported her with a fund of 1 500 000 euro.

With this grant, Slagter is able to approach the relation between expectations and perception through three main lines of inquiry. In the first, Slagter and her team try to understand why humans only have one interpretation of reality at any moment. ‘This becomes apparent when we are confronted with noisy input,’ Slagter explains. ‘When you walk down a street at night in pouring rain, you might observe a man with a hat standing on the side walk, but at second glance you realize it’s a sign post. With ambiguous input, you either recognize a man or you recognize a sign post, you never see a morphed version of the two because our prior experience tells us there is no such thing as a man-sign post.’

To determine why only one model is selected and how the brain determines which model this should be, Slagter will combine experimental manipulations of perceptual expectations with neuroimaging. She expects interplay between the basal ganglia and the prefrontal cortex to play a particular role in determining what percept will dominate our conscious experience. Using a pharmacological intervention, Slagter will try to modulate interactions between these brain regions, to see whether this prevents people from updating their expectations of what is out there.

In a more clinical part of this research line, Slagter collaborates with professor Damiaan Denys of the AMC to explore the relevance of basal ganglia in obsessive compulsive disorder (OCD). ‘You could think of OCD as an illness where our models of the world are not adjusted according to reality. For example, people clean their house constantly but don’t perceive their house to be clean. We hope by stimulating activity in the basal ganglia, we can help people update the models they use of reality, thereby helping them to perceive the outside world in a more accurate way.’

In the second line of research, the team tries to understand how attention and expectations influence perception. The amount of information reaching our senses is vast and cannot all be processed by higher brain regions. As human beings we have evolved to process information as efficiently as possible. We can do so first of all based on prior experience, through predictive processing. This means we constantly predict what we are likely to perceive and mainly process the mismatches between our predictions and incoming information. But attention also plays a critical role in guiding information processing, and may determine the extent to which these mismatches make us reconsider our predictions depending on how reliable we consider the mismatch.

Finally, Slagter wants to establish whether the human prediction machine operates automatically, outside our control. ‘I will determine whether it is possible to consciously ‘be in the moment’ and choose to not let previous experiences color our perception. Whether it is possible to perceive every single stimulus as it is, without any expectations.’ To test this, Slagter invites a Buddhist master to her lab and studies the effects of two different meditation styles. ‘I think meditation could help us perceive the world in a less biased way, creating the space to adjust our habitual perception and thoughts. I’m curious to see whether we will find experimental proof to back that up.’

 

Text: Marieke Buijs

How the brain determines which information reaches conscious perception

Assistant professor

Only a fraction of the stimuli surrounding us reaches our conscious perception at any moment. How does our brain switch from one stimulus to the other? And which forces influence that process? Associate professor Tomas Knapen studies these questions at VU university in Amsterdam and received a grant from NWO to combine forces with the Chinese lab of Peng Zhang at the Chinese Academy of Sciences.

In order to reliably study conscious perception, Knapen executes his research in a strongly regulated lab setting. He uses binocular rivalry, an optic illusion for which participants wear special glasses which have one red and one green lens. Observing a red-green figure, this means one eye is confronted with the green shape, while the other eye observes a red figure in the same location. In human perception, this results in the observer being solely aware of a red figure at one point, while a moment later the image shifts and the observer only registers the green figure.

Apparently, the brain contains a mechanism that causes regular shifts in awareness between the streams of information from the left and the right eye. Knapen wants to understand how this mechanism works, also because he suspects a similar principle to be at play in switching perception in daily life: from the conversation you are in to a more interesting one at the adjacent table, or from the book you are reading to the screen of your phone. Knapen: ‘In the real world, the amount of possible switches is unlimited and the stimuli also constantly change, with passers-by that enter and leave your field of vision. In this experiment, we limit the possibilities to two consistent stimuli. That enables us to really gain understanding of the brain mechanisms at play in selecting the input that reaches consciousness.’

So what causes the shift? Is it top-down regulation from the frontal cortex or other higher level visual brain areas that are bored with the information from one eye and ‘request’ a change? Or, alternatively, is it processes of local habituation in the primary visual cortex that causes the signal from one eye to extinguish and for the other signal to take over in the information flowing to higher visual areas? Or is it some form of interaction between these two scenario’s?

To shed light on these questions, Knapen uses a 7 Tesla fMRI-scanner. That gives him the resolution to distinguish between top-down and bottom-up information streams in the different layers of the primary visual cortex. In Peking, Knapens colleague Zhang uses a MEG-scanner, which has a high temporal resolution, to differentiate between the two types of information streams. Eventually, the two teams will combine their data, making use of the good temporal and spatial resolution of the different techniques to learn about the mechanisms at play in switching attention between stimuli.

Simultaneously, Knapen will conduct a series of sub-experiments to control for biases as a result of the research instructions. ‘I find it important to be sure that we really measure what we assume to measure. Therefore, I deliberately try to control for factors that might skew the experiment.’ In the main experiment, participants receive instructions to report on their perception by pushing buttons corresponding to the green and the red image. But doing so triggers fluctuations in attention and other cognitive processes and these could influence perception. When the subject reports perceiving a green image by pushing the corresponding button, this reporting in and by itself gives the green image more valence, and that might influence the switch to the red image, Knapen theorizes. Therefore, he will compare this research setup to one in which participants don’t have to report their perception in real time, but are asked to report afterwards how many switches of the image they perceived.

Knapen hopes his experiments will help him understand conscious perception and the way in which our actions influence that perception. Knapen: ‘Ultimately I hope this type of research adds to our understanding of how people move through the interactive film that is life.’

Text: Marieke Buijs

Mini-symposium:“Attention, Learning and Reward”

February 23, 2017, Time: 15.00 – 17:30
Place: Vrije Universiteit Amsterdam (MF-G6-13: medical faculty, G-Wing, 6th floor, room 13)

Program:

Time

Speaker

Title

15:00- 15:05 Welcome   Introduction
15:05-15:30 Leonardo Chelazzi, University of Verona, Italy  Statistical Learning of Target Selection and Distractor Filtering
15:30-15:55 Sara Jahfari, Vrije Universiteit Amsterdam On the role of learning in the future deployment of attention, and the regulation of uncertain choices: a computational approach
15:55-16:20 Jan Engelmann, Universiteit van Amsterdam How rewards and punishments guide goal-directed cognition and choice
15:55-16:20 Jan Engelmann, Universiteit van Amsterdam How rewards and punishments guide goal-directed cognition and choice
16:20-16:35 Break  
16:35-17:00 Jane Raymond, University of Birmingham Competition among motivational states drives visual attention
17:00-17:25 Jan Theeuwes, Vrije Universiteit van Amsterdam Reward shapes visual attention

Mini-symposium is coupled to PhD defense of Michel Failing:

Thesis title:  “For What It’s Worth: Reward Value Drives Visual Selective Attention”
Time: 11.45 – 12:45
Place: Vrije Universiteit Amsterdam (Aula, main building)

Download the flyer: MiniSymposiumAttentionLearningAndReward

The neural mechanisms and function of consciousness

How does the collective activity of individual neurons result in a subjective conscious experience of the world? It is one of the core questions in contemporary psychology, cognitive neuroscience and philosophy. Cognitive neuroscientist Simon van Gaal received an ERC grant of 1,5 million euro to bring the answer a little bit closer.

How does something you experience, like a thought or a dream, arise from the electrochemical processes taking place in the brain? To unravel the neural foundations of consciousness, Van Gaal and his team will spend the next five years on a series of studies.

Pharmacological intervention
An important part of the ERC funded project focuses on the molecular processes underlying consciousness. Studies in other animals have shown that the NMDA-receptor might be crucial for recurrent processing, the dynamic information exchange between brain regions. Because recurrent processes are thought to give rise to consciousness, Van Gaal expects NMDA-mediated processes to be essential in becoming aware of a stimulus. To test this, he will do reversible pharmacological interventions in humans in which he temporarily blocks NMDA receptors and measures how this influences the likelihood a subject will consciously perceive a stimulus that is briefly shown.

In order to string the behavioral measures and the molecular intervention together, Van Gaal and his team will use different visualization techniques to keep track of neural activity during the experiments. Specifically, the team is interested in registering to what extent recurrent signaling between different areas in the brain is affected by NMDA blockade.

A potential function of conscious experience
Another part of the project focuses on establishing what purpose consciousness may serve in human functioning. Van Gaal: ‘Consciousness has developed in evolution, possibly because it helps us in some way. But what it is that we gain by having conscious experiences is no yet known.’

It is known that many cognitive and perceptual functions, like processing visual or auditory input or the initiation of motor actions, can operate unconsciously, so these are not the function of consciousness. Van Gaal proposes that consciousness might benefit us by extending the period that information is available in the brain. In order to find out whether this might be true, the research team will measure whether subjects can use unconscious information to base decisions on later in time or whether this retention of information only happens when a stimulus is consciously processed.

Vegetative state
Although Van Gaal is primarily driven by curiosity to understand the fundamental workings of the human brain, in a longer run, he can see these insights resulting in more practical solutions, especially when it concerns insight into the molecular processes involved. Van Gaal: ‘Knowledge of the neurotransmitter-systems implicated in consciousness might eventually help us find ways to treat people who have problems relating to consciousness, patients who are in a vegetative state for example.’

Text: Marieke Buijs

Typically, human behavior is explained as the result of a battle between deliberate efforts to achieve a certain goal and external factors that subconsciously drive our behavior away from that goal. Professor in cognitive psychology Bernhard Hommel proposes an alternative theory about the relation between goal setting and behavior and received an ERC grant of 2,5 million euro to experimentally explore this theory.

Maybe people are not merely actors who, while trying to achieve a certain goal, are distracted by external factors that secretly drive their behavior instead. What if we view people as smart planners, deliberately switching between maintaining focus on their goals and being guided by circumstances? Would that be a better model to understand human behavior?

That is the overarching question Hommel will try to answer in the next five years. He will do so in an approach that spans different levels of understanding, from the molecular processes in the brain all the way up to the interpersonal interactions that are shaped by society. Hommel: ‘It is a high risk, high gain approach. But that is exactly the goal of ERC-funded research. This grant allows me to work in a team of ten scientists to look at the same question on these conceptually distinct levels.’

Meditation
Because Hommel is interested in the force organizing basic processes like perception, attention and response selection, he will study the network connecting different areas in the brain. For this he has access to a high resolution 7 Tesla fMRI scanner, in which subjects will perform tasks that require either goal- oriented or stimulus-driven behavior, like the Stroop task. Hommel is especially interested in the frontal and striatal dopaminergic networks, because they embody staying focused and flexibly switching respectively. He will also have a close look at the production of dopamine, in the substantia nigra and ventral tegmental areas, as this represents the source of this organization.

On another level, the group will study whether people have control over the brain state they are in. ‘Some people might inherently be better at staying focused on their goal, while others are more flexible in dealing with external circumstances,’ Hommel remarks. ‘But I also think people have control over how they balance intrinsic and external influence on their behavior.’ The psychologist will test this hypothesis by training subjects in two distinct types of meditation. One requires people to stay focused on one thought, fighting off intruding thoughts, the other type of meditation requires the opposite, allowing all thoughts and feelings to be present. Hommel will measure how the different types of training influence the behavior of his subjects.

Artificial mini-culture
Finally, cultural factors also influence people, think for example of how perseverance is regarded as a virtue in Calvinistic societies, whereas going with the flow is more appreciated in other cultures. Hommel will imitate the influence of a societal environment on the extent to which people’s behavior is determined by their goals. He will do so by having participants acquire an artificially created mini-culture – a coherent set of rules that expresses particular norms and values. Subsequently, he will test whether this leads to the same systematic changes in perception, attention, and decision-making that natural religions have been found to produce.

Underlying the research project is Hommel’s concern with the discourse about “free will” that currently dominates psychology. ‘We often presume external stimuli take us off course, undermine our “free will”. But I don’t see a reason to believe stimulus-driven behavior to not be intentional. It can be really smart to adapt to circumstances, both in an ancestral and the current setting. Think about someone chasing a boar and adjusting this behavior when he notices a lion that is about to chase him, or someone nowadays pursuing a career as a singer, but going along with an alternative career opportunity that presents itself instead, going with the ‘distractions’ might be for the better in both scenario’s.’

Text: Marieke Buijs

Pleasure from Food – insights from brain responses to taste

Young and older adults experience similar taste sensations, but like tastes differently. This is one of the most evident outcomes from the research by Heleen Hoogeveen. She successfully defended her thesis on November 30th 2016, at the University of Groningen. Her work was part of a TI Food & Nutrition project, called Sensory & Liking, of which the outcomes provide new leads for product development targeted at the elderly. 

Grandmother likes an extra tablespoon of sugar in her tea, and grandfather wants his potatoes with a heavy sprinkling of salt. In fact, many elderly compared to young adults prefer foods with intense taste. Researchers tend to think that in the elderly decreased taste sensation is related to changes in taste liking. “However, we observed that healthy older adults sense tastes similar to young adults, but show higher liking for sweet and salty tastes”, stresses Hoogeveen.“ This is probably because taste liking is dependent on more factors than taste sensation alone.”

Neuronal processes

Searching for a better understanding of taste liking, Hoogeveen investigated the neuronal processes taking place from the moment the product touches the tongue and stimulates the taste buds to the moment people give their opinion on how they like the taste. She and her colleagues were the first to measure (via functional Magnetic Resonance Imaging (fMRI)) brain activity, in 39 healthy young adults (18-30 years of age) and 35 healthy elderly people (60 to 72 years of age), when tasting sweet, sour, salt and bitter at different concentrations.

In contrast to earlier findings, Hoogeveen found no activity differences in brain areas involved in taste sensations between the young adults and the elderly. This indicates that aging per se is not necessarily related to changes in taste sensation. However, brain areas involved in memory and emotions did show differences between the two age groups. “In elderly these areas showed higher activity, which might explain the differences in product appreciation between them and younger participants.”

Hoogeveen also investigated how the amount and composition of saliva affects taste processing in the brain. “Mucin concentration, as a proxy of viscosity of saliva, was related to activity in a brain area coding taste intensity”, she says. “Perhaps this finding could impact salt and sugar reduction tools.”

Optimizing products

According to the PhD fellow, much food product development currently focuses on how foods can retard the aging process. “In addition to this focus on the nutritional value of food product, there should be just as much attention on optimizing the appreciation of products for the elderly”, she stresses. “Our work indicates the need for such research.”

Hoogeveen, who is looking for a position as a researcher bridging science and the food industry, experienced her time at TiFN as very inspiring. “It is challenging to translate fundamental outcomes towards practical applications. In this project industry partners and scientists communicated concisely and effectively to bridge this gap, providing valuable outcomes for us all.”

Does the pupil help optimize perception?

Dilation and constriction of the pupil are not merely reflex responses. Cognitive processes like attention also influence the pupillary light response, recent research shows. Psychologist Sebastiaan Mathôt explores how the pupil can help in optimal perception and received a Veni grant from the Dutch Science Association NWO to continue this line of research at the University of Groningen.

Traditionally scientists viewed the pupil as a more or less passive player in the process of perception, dilating when it gets darker and constricting when there is more light available. But there seems to be more to it.

When the pupil is dilated, a lot of light reaches the photoreceptors in the retina, which would theoretically be beneficial for perception because it means the sensitivity of the resulting image is boosted. So why not always keep the pupil at its most dilated state? Because the lens is imperfect, Mathôt explains. ‘These imperfections become more influential in distorting the image when the light flows through a larger diaphragm into the lens,’ Mathôt explains. ‘So a dilated pupil results in less detail in the projected image.’

Therefore, Mathôt expects the pupil to strike a balance between sensitivity and sharpness of the image. But varying circumstances call for different qualities in perception. Mathôt: ‘As an extreme example, imagine you are at an open battle field. You would not be interested in the exact design of the jacket of your fellow soldiers. Instead, you would want to be as sensitive as possible to visual clues around you. This would call for a more dilated pupil than you would have when you are at ease, on your couch, reading a book.’

Mathôt will test this principle in two lab experiments that are very subdued versions of the battlefield and reading a book scenarios. He will measure how pupil diameter influences performance on these two types of tests.

In the first part of the test, participants stare at a cross in the middle of a white computer screen and are asked to press a button when they see a stimulus appear elsewhere on the screen. This requires high sensitivity and low detail of the image. In the second part of the experiment, people again fix their gaze at a cross in the middle of the screen and are asked to describe stimuli that briefly pop-up. In order to do this well, the subject will need to register a more detailed image of the shown stimulus.

By adjusting the amount of light in the room, giving subjects eye drops that dilate their pupils or having them watch either a white or black screen prior to the test, Mathôt will influence the pupil diameter, so he can analyse whether that tweaks performance in the two perception tasks.

Foremost, Mathôt hopes to simply help the understanding of human perception progress. But he also sees some more practical applications of his pupil research. In a previous study, he showed how attention to either a dark or a light object influences pupil diameter. He now wants to use this principle to see if it could help paralysed people in the final stadium of the neurological disease ALS to communicate with the outside world through pupil size. The system Mathôt is testing for this distinguishes between the letters in the alphabet by giving the unique ‘barcodes’ of alternating light and dark spheres surrounding them. Measuring the changes in pupillary diameter in the patient subsequently indicates which letter they were focusing on. ‘Testing this system with actual patients will probably be the most intense intense part of my research. But I would be really happy if I would be able to help people who are suffering from such a horrible disease.’

Text: Marieke Buijs