Biology subjects

Horstmann, A.

Publications and source records attributed to Horstmann, A..

7 recordsLinked to original sources

bioRxiv2023

Impaired updating of working memory representations in individuals with high BMI: evidence for dopaminergic mechanisms

Everyday life requires an adaptive balance between distraction-resistant maintenance of information and the flexibility to update this information when needed. These opposing mechanisms are proposed to be balanced through a working memory gating mechanism. Prior research indicates that obesity may elevate the risk of working memory deficits, yet the underlying mechanisms remain elusive. Dopaminergic alterations have emerged as a potential mediator. However, current models suggest these alterations should only shift the balance in working memory tasks, not produce overall deficits. The empirical support for this notion is currently lacking, however. To address this gap, we pooled data from three studies (N = 320) where participants performed a working memory gating task. Higher BMI was associated with overall poorer working memory, irrespective of whether there was a need to maintain or update information. However, when participants, in addition to BMI level, were categorized based on certain putative dopamine-signaling characteristics (Single Nucleotide Polymorphisms; specifically, Taq1A and DARPP-32), distinct working memory gating effects emerged. These SNPs, primarily associated with striatal dopamine transmission, appear to be linked with differences in updating, specifically, among high-BMI individuals. Moreover, blood amino acid ratio, which indicates central dopamine synthesis capacity, combined with BMI, shifted the balance between distractor-resistant maintenance and updating. These findings suggest that both dopamine-dependent and dopamine-independent cognitive effects exist in obesity. Understanding these effects is crucial if we aim to modify maladaptive cognitive profiles in individuals with obesity.

neuroscience↗

bioRxiv2022

Cortical grey matter mediates increases in model-based control and learning from positive feedback from adolescence to adulthood

Adolescents undergo maturation in cognition and brain structure. Model-based (MB) control is known to increase from childhood to young adulthood, which is mediated by cognitive abilities. Here, we asked two questions unaddressed in previous developmental studies: Firstly, what are the brain structural correlates of age-related increases in MB control? Secondly, how are age-related increases in MB control from adolescence to adulthood influenced by motivational context? A developmental sample (n=103, age: 12-42) completed structural MRI and an established task to capture MB control. The task was modified with respect to outcome valence by including (1) reward and punishment blocks to manipulate the motivational context and (2) an additional choice test to assess learning from positive vs. negative feedback. After replicating that an age-dependent increase in MB control is mediated by cognitive abilities, we demonstrate first-time evidence that grey matter density (GMD) in the parietal cortex mediates the increase of MB control with age. While motivational context did not relate to age-related changes in MB control, learning from positive feedback improved with age. Meanwhile, negative feedback learning showed no age effects. We present a first report that an age-related increase in learning from positive feedback was mediated by reduced GMD in the parietal, medial and dorsolateral prefrontal cortex. Our findings indicate that efficient brain maturation, as putatively reflected in lower GMD, in distinct and partially overlapping brain regions is a key developmental step towards age-related increases in planning and value-based choice. Significance StatementAdolescents undergo extensive maturation in cognition and brain structure. Interestingly, model-based decision-making is also known to increase from childhood to adulthood. Here, we demonstrate for the first time that grey matter density in the parietal cortex mediates an age-dependent increase in model-based control. An age-related increase in positive feedback learning was mediated by reduced grey matter density in the parietal, medial and dorsolateral prefrontal cortex. Interestingly, a manipulation of motivational context (gain reward vs. avoid punishment) did not impact age-related changes in model-based control. These findings highlight that efficient brain maturation in distinct and overlapping cortical brain regions constitutes a key developmental step towards increases in model-based planning and value-based choice.

neuroscience↗

bioRxiv2020

DRD2/ANKK1 Taq1A but not COMT single nucleotide polymorphisms contribute to the link between temporal impulsivity and obesity in men

Temporal impulsivity, the tendency to choose a smaller, sooner over a larger, delayed reward, is associated with single nucleotide polymorphisms (SNPs) in COMT and DRD2-related ANKK1 genes, whose products regulate dopaminergic transmission in the brain. Temporal impulsivity is also consistently associated with obesity, sometimes in a genderdependent fashion. Further, there seems to be no direct association between these SNPs and obesity. In this study, we investigated an interaction between BMI, COMT, and DRD2/ANKK1 SNPs, and temporal impulsivity. We tested three plausible models of associations between those variables: (1) genetic variability influencing BMI through temporal impulsivity and gender interactions, (2) genetic variability interacting with temporal impulsivity to influence BMI, (3) interaction of BMI and genetic variability influencing temporal impulsivity. We found evidence for the second model: in men, BMI was dependent on temporal impulsivity and the DRD2/ANKK1 SNP. It shows that increased temporal impulsivity combined with a disadvantageous DRD2/ANKK1 genotype might be a vulnerability factor for the development of obesity. Our study, even though cross-sectional, adds to the body of literature regarding the influence of the dopaminergic system on obesity measures. Our results point to a factor explaining discrepancies in results regarding associations of temporal impulsivity and BMI in women and men.

genetics↗

bioRxiv2019

Differences in intake of high-fat high-sugar diet are related to variations in central dopamine in humans.

Obesity is associated with alterations in dopaminergic transmission and cognitive function. Recent findings from rodent studies suggest that diets rich in saturated fat and refined sugars (HFS) induce changes in the dopamine system independent of excessive body weight. However, so far the impact of HFS on the human brain has not been investigated. Here, we compared the effect of dietary dopamine depletion on dopamine dependent cognitive tasks between two groups that differ in habitual intake of dietary fat and sugar. Specifically, we used a double-blind within-subject crossover design to compare the effect of acute phenylalanine/tyrosine depletion (APTD) on a reinforcement learning and a working memory task, in two groups that are on opposite ends of the spectrum of self-reported HFS intake (low vs. high intake: LFS vs. HFS group). We tested 31 healthy young women, who were matched for BMI (mostly normal weight to overweight) and IQ. Depletion of central dopamine reduced the working memory specific performance on the operation span task (OSPAN) in the LFS, but not in the HFS group (p = 0.023, r = 0.210). Learning from positive and negative reinforcement (probabilistic selection task: PST) was increased in both diet groups after dopamine depletion (p = 0.048, r = 0.144). As secondary exploratory research question we measured peripheral dopamine precursor availability (pDAP) at baseline as an estimate for central dopamine levels. The HFS group had a significantly higher pDAP at baseline compared to the LFS group (p = .048, r = -0.355). Our data provides first evidence that the intake of HFS is associated with changes in indirect measures of central dopamine levels in humans. The observed associations are independent of body weight status, suggesting that consumption of HFS might be associated with maladaptive behaviors contributing to the development of obesity.

neuroscience↗

bioRxiv2019

Activity in the left amygdala in response to foods differs depending on the emotional context

Emotions can influence our eating behaviors. Facing an acute stressor or being in a positive mood are examples of situations that tend to modify appetite. However, the question of how the brain integrates these emotion-related changes in food processing remains elusive. Here we designed an emotional priming fMRI task to test if amygdala activity during food pictures differs depending on the emotional context. Fifty-eight female participants completed a novel emotional priming task, in which emotional images of negative, neutral or positive situations were followed by pictures of either foods or objects. After priming in each trial, participants rated how much they liked the shown foods or objects. We analyzed how brain activity during the contrast \"foods > objects\" changed according to the emotional context - in the whole brain and in the amygdala. We also examined the potential effect of adiposity (i.e., waist circumference). We observed a higher difference between liking scores for foods and objects after positive priming than after neutral priming. In the left amygdala, activity in the contrast \"foods > objects\" was higher after neutral priming relative to negative priming. Waist circumference was not significantly related to this emotional priming effect on food processing. Our results suggest that emotional context alters food and non-food perception, both in terms of liking scores and with regards to engagement of the left amygdala. Moreover, our findings indicate that emotional context has an impact on the salience advantage of food, possibly affecting eating behavior.

neuroscience↗

bioRxiv2019

Hemispheric asymmetries in resting-state EEG and fMRI are related to approach and avoidance behaviour, but not to eating behaviour or BMI

Much of our behaviour is driven by two motivational dimensions - approach and avoidance. These have been related to frontal hemispheric asymmetries in clinical and resting-state EEG studies: approach was linked to higher activity of the left relative to the right hemisphere, while avoidance was related to the opposite pattern. Increased approach behaviour, specifically towards unhealthy foods, is also observed in obesity and has been linked to asymmetry in the framework of the right-brain hypothesis of obesity. Here, we aimed to replicate previous EEG findings of hemispheric asymmetries for self-reported approach/avoidance behaviour and to relate them to eating behaviour. Further, we assessed whether resting fMRI hemispheric asymmetries can be detected and whether they are related to approach/avoidance, eating behaviour, and BMI. We analysed 3 samples: Sample 1 (n=117) containing EEG and fMRI data from lean participants, and Samples 2 (n=89) and 3 (n=152) containing fMRI data from lean, overweight, and obese participants. While in Sample 1 approach in women was related to EEG and fMRI hemispheric asymmetries, in Samples 2 and 3 this effect was not significant. Here, hemispheric asymmetries were neither related to BMI nor eating behaviour. Our study partly replicates previous EEG findings regarding hemispheric asymmetries and indicates that this relationship could also be captured using fMRI. Our findings suggest that eating behaviour and obesity are likely to be mediated by mechanisms not directly relating to frontal asymmetries in neuronal activation quantified with EEG and fMRI.

neuroscience↗

bioRxiv2018

Unhealthy Yet Avoidable - How Cognitive Bias Modification Alters Behavioral And Brain Responses To Food Cues In Obesity

ObjectiveObesity is associated with automatically approaching problematic stimuli, such as unhealthy food. Cognitive bias modification (CBM) could beneficially impact on problematic approach behavior. However, it is unclear which mechanisms are targeted by CBM in obesity: Candidate mechanisms include (1) altering reward value of food stimuli or (2) strengthening inhibitory abilities.\n\nMethods33 obese people completed either CBM or sham training during fMRI scanning. CBM consisted of an implicit training to approach healthy and avoid unhealthy foods.\n\nResultsAt baseline, approach tendencies towards food were present in all participants. Avoiding vs. approaching food was associated with higher activity in the right angular gyrus (rAG). CBM resulted in a diminished approach bias towards unhealthy food, decreased activation in the rAG, and increased activation in the anterior cingulate cortex. Relatedly, functional connectivity between the rAG and right superior frontal gyrus increased. Analysis of brain connectivity during rest revealed training-related connectivity changes of the inferior frontal gyrus and bilateral middle frontal gyri.\n\nConclusionTaken together, CBM strengthens avoidance tendencies when faced with unhealthy foods and alters activity in brain regions underpinning behavioral inhibition.

neuroscience↗