Lieneke K. Janssen

Different mental rotation strategies reflected in the rotation related negativity

In a mental rotation task of objects, typically, reaction time (RT) increases and the rotation related negativity (RRN) increases in amplitude with increasing angles of rotation. However, in a mental rotation task of hands, different RT profiles can be observed for outward and inward rotated hands. In the present study, we examined the neurophysiological correlates of these asymmetries in the RT profiles. We used a mental rotation task with stimuli of left and right hands. In line with previous studies, the behavioral results showed a linear increase in RT for outward rotations, but not for inward rotations as a function of angular disparity. Importantly, the ERP results revealed an RRN for outward rotated stimuli, but not for inward rotated stimuli. This is the first study to show that the behaviorally observed differences in a mental rotation task of hands is also reflected at the neurophysiological level.

Loss of lateral prefrontal cortex control in food-directed attention and goal-directed food choice in obesity

Abstract Loss of lateral prefrontal cortex (lPFC)‐mediated attentional control may explain the automatic tendency to eat in the face of food. Here, we investigate the neurocognitive mechanism underlying attentional bias to food words and its association with obesity using a food Stroop task. We tested 76 healthy human subjects with a wide body mass index (BMI) range (19–35 kg/m2) using fMRI. As a measure of obesity we calculated individual obesity scores based on BMI, waist circumference and waist‐to‐hip ratio using principal component analyses. To investigate the automatic tendency to overeat directly, the same subjects performed a separate behavioral outcome devaluation task measuring the degree of goal‐directed versus automatic food choices. We observed that increased obesity scores were associated with diminished lPFC responses during food attentional bias. This was accompanied by decreased goal‐directed control of food choices following outcome devaluation. Together these findings suggest that deficient control of both food‐directed attention and choice may contribute to obesity, particularly given our obesogenic environment with food cues everywhere, and the choice to ignore or indulge despite satiety. HighlightsFood‐directed attention and choice were investigated in relationship to obesity.Obesity was associated with reduced lateral PFC control in a food Stroop task.This was accompanied by reduced goal‐directed food choices in the same subjects.Less control of food‐directed attention and choice may thus contribute to obesity.

Amplified Striatal Responses to Near-Miss Outcomes in Pathological Gamblers

Near-misses in gambling games are losing events that come close to a win. Near-misses were previously shown to recruit reward-related brain regions including the ventral striatum, and to invigorate gambling behavior, supposedly by fostering an illusion of control. Given that pathological gamblers are particularly vulnerable to such cognitive illusions, their persistent gambling behavior might result from an amplified striatal sensitivity to near-misses. In addition, animal studies have shown that behavioral responses to near-miss-like events are sensitive to dopamine, but this dopaminergic influence has not been tested in humans. To investigate these hypotheses, we recruited 22 pathological gamblers and 22 healthy controls who played a slot machine task delivering wins, near-misses and full-misses, inside an fMRI scanner. Each participant played the task twice, once under placebo and once under a dopamine D2 receptor antagonist (sulpiride 400 mg), in a double-blind, counter-balanced design. Participants were asked about their motivation to continue gambling throughout the task. Across all participants, near-misses elicited higher motivation to continue gambling and increased striatal responses compared with full-misses. Crucially, pathological gamblers showed amplified striatal responses to near-misses compared with controls. These group differences were not observed following win outcomes. In contrast to our hypothesis, sulpiride did not induce any reliable modulation of brain responses to near-misses. Together, our results demonstrate that pathological gamblers have amplified brain responses to near-misses, which likely contribute to their persistent gambling behavior. However, there is no evidence that these responses are influenced by dopamine. These results have implications for treatment and gambling regulation.

Increased Striatal Dopamine Synthesis Capacity in Gambling Addiction

BACKGROUND The hypothesis that dopamine plays an important role in the pathophysiology of pathological gambling is pervasive. However, there is little to no direct evidence for a categorical difference between pathological gamblers and healthy control subjects in terms of dopamine transmission in a drug-free state. Here we provide evidence for this hypothesis by comparing dopamine synthesis capacity in the dorsal and ventral parts of the striatum in 13 pathological gamblers and 15 healthy control subjects. METHODS This was achieved using [18F]fluoro-levo-dihydroxyphenylalanine dynamic positron emission tomography scans and striatal regions of interest that were hand-drawn based on visual inspection of individual structural magnetic resonance imaging scans. RESULTS Our results show that dopamine synthesis capacity was increased in pathological gamblers compared with healthy control subjects. Dopamine synthesis was 16% higher in the caudate body, 17% higher in the dorsal putamen, and 17% higher in the ventral striatum in pathological gamblers compared with control subjects. Moreover, dopamine synthesis capacity in the dorsal putamen and caudate head was positively correlated with gambling distortions in pathological gamblers. CONCLUSIONS Taken together, these results provide empirical evidence for increased striatal dopamine synthesis in pathological gambling.

Spontaneous eye blink rate and dopamine synthesis capacity: Preliminary evidence for an absence of positive correlation

Dopamine is central to a number of cognitive functions and brain disorders. Given the cost of neurochemical imaging in humans, behavioural proxy measures of dopamine have gained in popularity in the past decade, such as spontaneous eye blink rate (sEBR). Increased sEBR is commonly associated with increased dopamine function based on pharmacological evidence and patient studies. Yet, this hypothesis has not been validated using in vivo measures of dopamine function in humans. To fill this gap, we measured sEBR and striatal dopamine synthesis capacity using [18F]DOPA PET in 20 participants (nine healthy individuals and 11 pathological gamblers). Our results, based on frequentist and Bayesian statistics, as well as region‐of‐interest and voxel‐wise analyses, argue against a positive relationship between sEBR and striatal dopamine synthesis capacity. They show that, if anything, the evidence is in favour of a negative relationship. These results, which complement findings from a recent study that failed to observe a relationship between sEBR and dopamine D2 receptor availability, suggest that caution and nuance are warranted when interpreting sEBR in terms of a proxy measure of striatal dopamine.

Dopaminergic Drug Effects on Probability Weighting during Risky Decision-Making

Abstract Dopamine has been associated with risky decision-making, as well as with pathological gambling, a behavioral addiction characterized by excessive risk-taking behavior. However, the specific mechanisms through which dopamine might act to foster risk-taking and pathological gambling remain elusive. Here we test the hypothesis that this might be achieved, in part, via modulation of subjective probability weighting during decision making. Human healthy controls (n = 21) and pathological gamblers (n = 16) played a decision-making task involving choices between sure monetary options and risky gambles both in the gain and loss domains. Each participant played the task twice, either under placebo or the dopamine D2/D3 receptor antagonist sulpiride, in a double-blind counterbalanced design. A prospect theory modelling approach was used to estimate subjective probability weighting and sensitivity to monetary outcomes. Consistent with prospect theory, we found that participants presented a distortion in the subjective weighting of probabilities, i.e., they overweighted low probabilities and underweighted moderate to high probabilities, both in the gain and loss domains. Compared with placebo, sulpiride attenuated this distortion in the gain domain. Across drugs, the groups did not differ in their probability weighting, although gamblers consistently underweighted losing probabilities in the placebo condition. Overall, our results reveal that dopamine D2/D3 receptor antagonism modulates the subjective weighting of probabilities in the gain domain, in the direction of more objective, economically rational decision making.

The effect of an 8-week mindful eating intervention on anticipatory reward responses in the midbrain

Obesity is a highly prevalent disease, usually resulting from chronic overeating. Accumulating evidence suggests that increased neural responses during the anticipation of high caloric food play an important role in overeating. A promising method to counteract enhanced food anticipation in overeating might be mindfulness-based interventions (MBIs). However, how MBIs can affect food reward anticipation neurally has never been studied. In this randomized, actively controlled study we aimed to investigate whether an 8-week mindful eating intervention decreases reward anticipation in striatal and midbrain reward regions. Using functional Magnetic Resonance Imaging, we tested 58 healthy subjects with a wide body mass index range (BMI: 19-35 kg/m2), who were motivated to change their eating behavior. During scanning they performed an incentive delay task, measuring neural reward anticipation responses to caloric and monetary cues before and after 8 weeks of mindful eating or educational cooking (active control). Relative to educational cooking (active control), mindful eating decreased reward anticipation responses to food, but not to monetary reward cues, in the midbrain, but not the striatum. The effects were specific to reward anticipation and did not extend to reward receipt. These results show that an 8-week mindful eating intervention may decrease the salience of food cues specifically, which could result in decreased food-cue triggered overeating on the long term. Significance statement Mindfulness-based interventions have been shown effective in reducing disordered eating behavior in clinical as well as non-clinical populations. Here, we present the first randomized actively controlled study investigating the effects of mindfulness on reward anticipation in the brain. Using fMRI we show that midbrain responses to caloric, but not monetary, reward cues are reduced following an 8-week intervention of mindful eating relative to educational cooking (active control). Mindful eating interventions may thus be promising in counteracting reward cue-driven overeating, particularly in our obesogenic environment with food cues everywhere. Moreover, our data show that specific mindfulness-based interventions can target specific reward-cue responses in the brain, which might be relevant in other compulsive behaviors such as addiction.