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

Concurrent self-administered transcranial direct current stimulation and attention bias modification training in binge eating disorder: feasibility randomised sham-controlled trial

BACKGROUND

Binge eating disorder (BED) is a common and disabling condition, typically presenting with multiple psychiatric and obesity-related comorbidities. Evidence-based treatments are either resource-intensive (psychotherapies) or have side-effects (medications): these achieve remission in around 50% of cases. Novel treatments are needed.

AIMS

This randomised sham-controlled trial aimed to assess feasibility, acceptability and preliminary efficacy of at-home, self-administered transcranial direct current stimulation (tDCS) and attention bias modification training (ABMT) in adults with binge eating disorder.

METHOD

Eighty-two participants with binge eating disorder were randomly allocated to real tDCS with ABMT, sham tDCS with ABMT, ABMT only or waitlist control. Intervention groups received ten sessions of their allocated treatment over 2-3 weeks. tDCS (2 mA, 20 min) was self-administered using a bilateral (anode right/cathode left) montage targeting the dorsolateral prefrontal cortex. Outcomes were assessed at baseline, post-treatment and 6-week follow-up.

RESULTS

Prespecified feasibility criteria (recruitment ≥80 participants and retention rate ≥75%) were exceeded, and treatment completion rates were high (98.7%). All interventions reduced binge eating episodes, eating disorder symptoms and related psychopathology between baseline and follow-up, relative to waitlist control (medium-to-large between-group effect sizes for change scores). Small-to-medium effect sizes for change scores favoured real tDCS with ABMT versus comparators, suggesting the verum intervention produces superior outcomes.

CONCLUSIONS

At-home, self-administered tDCS with ABMT is feasible and acceptable, and preliminary data on efficacy are promising. This approach could be a useful and scalable alternative or adjunct to established treatments for binge eating disorder. Confirmatory trials can, and should, be pursued.

Functional alterations in overweight/obesity: focusing on the reward and executive control network

Overweight (OW) and obesity (OB) have become prevalent issues in the global public health arena. Serving as a prominent risk factor for various chronic diseases, overweight/obesity not only poses serious threats to people's physical and mental health but also imposes significant medical and economic burdens on society as a whole. In recent years, there has been a growing focus on basic scientific research dedicated to seeking the neural evidence underlying overweight/obesity, aiming to elucidate its causes and effects by revealing functional alterations in brain networks. Among them, dysfunction in the reward network (RN) and executive control network (ECN) during both resting state and task conditions is considered pivotal in neuroscience research on overweight/obesity. Their aberrations contribute to explaining why persons with overweight/obesity exhibit heightened sensitivity to food rewards and eating disinhibition. This review centers on the reward and executive control network by analyzing and organizing the resting-state and task-based fMRI studies of functional brain network alterations in overweight/obesity. Building upon this foundation, the authors further summarize a reward-inhibition dual-system model, with a view to establishing a theoretical framework for future exploration in this field.

Food choice drivers at varying income levels in an emerging economy

The purpose of this work was to explore and compare food choice drivers of low (LI), middle (MI) and high (HI) income urban people in an emerging economy (South Africa). Here, 13 focus group (FG) discussions [six LI, n = 36, 67% women; four MI, n = 22, 100% women and three HI, n = 17, 76% women; total n = 75) were transcribed, coded inductively and deductively and 17 food choice categories emerged. Eight of these, i.e., aspects related to: plant vs animal protein, food waste, food preparation, availability of resources, food exploration, social aspects and food spoilage, are not typically (e.g., sensory appeal, mood, health, convenience etc.) measured with established food choice questionnaires. Economic factors and Availability of food and resources were mentioned the most by LI participants compared to MI and HI. Whereas, Health; Familiarity and Food exploration were mostly mentioned by MI and HI participants. This study yielded a mixture of individual and environment based motives which add to our understanding of the "why" aspects underlying food choice in an urban and emerging economy. The fact that these aspects are compared by income group provides interesting information on the similarities and differences of how the food choice process unfolds across varying income groups. The insights from this study are useful for the development of an updated, quantitative food choice questionnaire for application in this and other emerging economies.

Cognitive Control and Weight Loss After Bariatric Surgery: the BARICO Study

BACKGROUND AND OBJECTIVES

Bariatric surgery (BS) is an effective treatment for obesity. However, some individuals experience insufficient weight loss after surgery. Therefore, we investigated whether cognitive control affects weight loss after Roux-en-Y gastric bypass (RYGB).

METHODS

Within this exploratory observational study, part of the BARICO study (BAriatric surgery Rijnstate and Radboudumc neuroImaging and Cognition in Obesity), participants aged between 35 and 55 years eligible for RYGB were included. Before and after BS, body weight, (delta) BMI and percentage total body weight loss (%TBWL) were determined. Additionally, at baseline, Stroop task-performance, -activation and -connectivity were assessed by a color-word paradigm task during functional neuroimaging to determine the ability of participants to inhibit cognitive interference.

RESULTS

Seventy-six participants were included, of whom 14 were excluded from fMRI analysis, leaving 62 participants. Participants were aged 45.0 ± 5.9 years with a mean pre-surgery BMI of 40.2 ± 3.3 kg/m2, and 86% were women. Mean decrease in BMI was 13.8 ± 2.5 kg/m2, and mean %TBWL was 34.9 ± 6.3% 1 year after BS. Stroop task performance did not correlate with (delta) BMI and %TBWL. The inferior parietal/middle occipital gyrus, inferior frontal gyrus, and supplementary motor cortex were involved in cognitive interference, although activity in these regions did not predict weight loss after surgery. Lastly, generalized psychophysiological interaction did not provide evidence for (delta) BMI- and %TBWL-dependent connectivity modulation.

DISCUSSION

Cognitive control did not predict weight loss after surgery. Future studies should focus on longer follow-up periods to understand the relation between cognitive control and weight loss.

TRIAL REGISTRATION

NL7090 ( https://www.clinicaltrialregister.nl/nl/trial/28949 ).

The effects of an 8-week mindful eating intervention on anticipatory reward responses in striatum and midbrain

Introduction

Accumulating evidence suggests that increased neural responses during the anticipation of high-calorie food play an important role in the tendency to overeat. A promising method for counteracting enhanced food anticipation in overeating might be mindfulness-based interventions (MBIs). However, the neural mechanisms by which MBIs can affect food reward anticipation are unclear. In this randomized, actively controlled study, the primary objective was to investigate the effect of an 8-week mindful eating intervention on reward anticipation. We hypothesized that mindful eating would decrease striatal reward anticipation responses. Additionally, responses in the midbrain-from which the reward pathways originate-were explored.

Methods

Using functional magnetic resonance imaging (fMRI), we tested 58 healthy participants with a wide body mass index range (BMI: 19-35 kg/m2), 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).

Results

Compared with the educational cooking intervention, mindful eating affected neural reward anticipation responses, with reduced caloric relative to monetary reward responses. This effect was, however, not seen in the striatum, but only in the midbrain. The secondary objective was to assess temporary and long-lasting (1 year follow-up) intervention effects on self-reported eating behavior and anthropometric measures [BMI, waist circumference, waist-to-hip-ratio (WHR)]. We did not observe effects of the mindful eating intervention on eating behavior. Instead, the control intervention showed temporary beneficial effects on BMI, waist circumference, and diet quality, but not on WHR or self-reported eating behavior, as well as long-lasting increases in knowledge about healthy eating.

Discussion

These results suggest that an 8-week mindful eating intervention may have decreased the relative salience of food cues by affecting midbrain but not striatal reward responses, without necessarily affecting regular eating behavior. However, these exploratory results should be verified in confirmatory research.The primary and secondary objectives of the study were registered in the Dutch Trial Register (NTR): NL4923 (NTR5025).

Multivariate resting-state functional connectomes predict and characterize obesity phenotypes

The univariate obesity-brain associations have been extensively explored, while little is known about the multivariate associations between obesity and resting-state functional connectivity. We therefore utilized machine learning and resting-state functional connectivity to develop and validate predictive models of 4 obesity phenotypes (i.e. body fat percentage, body mass index, waist circumference, and waist-height ratio) in 3 large neuroimaging datasets (n = 2,992). Preliminary evidence suggested that the resting-state functional connectomes effectively predicted obesity/weight status defined by each obesity phenotype with good generalizability to longitudinal and independent datasets. However, the differences between resting-state functional connectivity patterns characterizing different obesity phenotypes indicated that the obesity-brain associations varied according to the type of measure of obesity. The shared structure among resting-state functional connectivity patterns revealed reproducible neuroimaging biomarkers of obesity, primarily comprising the connectomes within the visual cortex and between the visual cortex and inferior parietal lobule, visual cortex and orbital gyrus, and amygdala and orbital gyrus, which further suggested that the dysfunctions in the perception, attention and value encoding of visual information (e.g. visual food cues) and abnormalities in the reward circuit may act as crucial neurobiological bases of obesity. The recruitment of multiple obesity phenotypes is indispensable in future studies seeking reproducible obesity-brain associations.

Computational mechanisms underpinning greater exploratory behaviour in excess weight relative to healthy weight adolescents

Obesity in adolescence is associated with cognitive changes that lead to difficulties in shifting unhealthy habits in favour of alternative healthy behaviours, similar to addictive behaviours. An outstanding question is whether this shift in goal-directed behaviour is driven by over-exploitation or over-exploration of rewarding outcomes. Here, we addressed this question by comparing explore/exploit behaviour on the Iowa Gambling Task in 43 adolescents with excess weight against 38 adolescents with healthy weight. We computationally modelled both exploitation behaviour (e.g., reinforcement sensitivity and inverse decay parameters), and explorative behaviour (e.g., maximum directed exploration value). We found that overall, adolescents with excess weight displayed more behavioural exploration than their healthy-weight counterparts - specifically, demonstrating greater overall switching behaviour. Computational models revealed that this behaviour was driven by a higher maximum directed exploration value in the excess-weight group (U = 520.00, p = .005, BF₁₀ = 5.11). Importantly, however, we found substantial evidence that groups did not differ in reinforcement sensitivity (U = 867.00, p = .641, BF₁₀ = 0.30). Overall, our study demonstrates a preference for exploratory behaviour in adolescents with excess weight, independent of sensitivity to reward. This pattern could potentially underpin an intrinsic desire to explore energy-dense unhealthy foods - an as-yet untapped mechanism that could be targeted in future treatments of obesity in adolescents.

Brain functional and structural magnetic resonance imaging of obesity and weight loss interventions

Obesity has tripled over the past 40 years to become a major public health issue, as it is linked with increased mortality and elevated risk for various physical and neuropsychiatric illnesses. Accumulating evidence from neuroimaging studies suggests that obesity negatively affects brain function and structure, especially within fronto-mesolimbic circuitry. Obese individuals show abnormal neural responses to food cues, taste and smell, resting-state activity and functional connectivity, and cognitive tasks including decision-making, inhibitory-control, learning/memory, and attention. In addition, obesity is associated with altered cortical morphometry, a lowered gray/white matter volume, and impaired white matter integrity. Various interventions and treatments including bariatric surgery, the most effective treatment for obesity in clinical practice, as well as dietary, exercise, pharmacological, and neuromodulation interventions such as transcranial direct current stimulation, transcranial magnetic stimulation and neurofeedback have been employed and achieved promising outcomes. These interventions and treatments appear to normalize hyper- and hypoactivations of brain regions involved with reward processing, food-intake control, and cognitive function, and also promote recovery of brain structural abnormalities. This paper provides a comprehensive literature review of the recent neuroimaging advances on the underlying neural mechanisms of both obesity and interventions, in the hope of guiding development of novel and effective treatments.

The Neural Processes in Food Decision-making and their Effect on Daily Diet Management in Successful and Unsuccessful Restrained Eaters

This study aimed to explore the neural mechanisms underlying food decision making in unsuccessful restrained eaters (US-REs) and successful restrained eaters (S-REs). During a functional magnetic resonance imaging scan, participants were required to choose between pairs of high- and low-calorie foods under the following conditions: the congruent condition (choose between high- and low-calorie foods with the same level of tastiness) and incongruent condition (choose between high-calorie foods tastier than the corresponding low-calorie foods). Subsequently, the participants' diets were monitored for one week. The behavioral results showed that US-REs (n = 28) chose more high-calorie foods than S-REs (n = 26); in contrast, S-REs spent more time in choosing for the incongruent than the congruent condition. The fMRI results found that US-REs exhibited more activity in reward regions (caudate and thalamus) than S-REs in the congruent condition. In the incongruent condition, S-REs showed stronger functional connectivity between the conflict-monitoring region (anterior cingulate cortex) and inhibitory-control regions (inferior frontal gyrus [IFG] and medial frontal gyrus) than US-REs. In both the conditions, increased activation of the insula, putamen, middle frontal gyrus, and IFG could predict increased food intake among US-REs in the following week. Furthermore, in both the conditions, increased IFG activation could predict decreased food cravings among S-REs during the following week. Our results suggest that US-REs have a strong reward response to food. Compared to US-REs, S-REs are more guided more by the goal of weight control, and exhibit strong functional connections between the conflict-monitoring and inhibitory-control regions. Therefore, eating enjoyment and weight-control goals influence restrained eating in daily life.

Spatiotemporal profile of altered neural reactivity to food images in obesity: Reward system is altered automatically and predicts efficacy of weight loss intervention

Introduction

Obesity presents a significant public health problem. Brain plays a central role in etiology and maintenance of obesity. Prior neuroimaging studies have found that individuals with obesity exhibit altered neural responses to images of food within the brain reward system and related brain networks. However, little is known about the dynamics of these neural responses or their relationship to later weight change. In particular, it is unknown if in obesity, the altered reward response to food images emerges early and automatically, or later, in the controlled stage of processing. It also remains unclear if the pretreatment reward system reactivity to food images is predictive of subsequent weight loss intervention outcome.

Methods

In this study, we presented high-calorie and low-calorie food, and nonfood images to individuals with obesity, who were then prescribed lifestyle changes, and matched normal-weight controls, and examined neural reactivity using magnetoencephalography (MEG). We performed whole-brain analysis to explore and characterize large-scale dynamics of brain systems affected in obesity, and tested two specific hypotheses: (1) in obese individuals, the altered reward system reactivity to food images occurs early and automatically, and (2) pretreatment reward system reactivity predicts the outcome of lifestyle weight loss intervention, with reduced activity associated with successful weight loss.

Results

We identified a distributed set of brain regions and their precise temporal dynamics that showed altered response patterns in obesity. Specifically, we found reduced neural reactivity to food images in brain networks of reward and cognitive control, and elevated reactivity in regions of attentional control and visual processing. The hypoactivity in reward system emerged early, in the automatic stage of processing (< 150 ms post-stimulus). Reduced reward and attention responsivity, and elevated neural cognitive control were predictive of weight loss after six months in treatment.

Discussion

In summary, we have identified, for the first time with high temporal resolution, the large-scale dynamics of brain reactivity to food images in obese versus normal-weight individuals, and have confirmed both our hypotheses. These findings have important implications for our understanding of neurocognition and eating behavior in obesity, and can facilitate development of novel integrated treatment strategies, including tailored cognitive-behavioral and pharmacological therapies.

Differential Orbitofrontal Cortex Responses to Chocolate Images While Performing an Approach-Avoidance Task in the MRI Environment

Background: Chocolate is one of the most frequently craved foods, and it often challenges self-regulation. These cravings may be underpinned by a neural facilitation of approach behavior toward chocolate. This preregistered study investigated the behavioral and neural correlates of such a bias using functional magnetic resonance imaging (fMRI) and reaction times (RTs). Methods: A total of n = 30 frequent chocolate eaters performed a relevant-feature approach-avoidance task (AAT) in the MRI scanner using buttons to enlarge (approach) or to shrink (avoid) pictures of chocolate and inedible control objects. We tested (a) whether implicit RT-based approach biases could be measured in a supine position in the scanner, (b) whether those biases were associated with activity in reward-related brain regions such as the insula, amygdala, striatum, and orbitofrontal cortex (OFC), and (c) whether individual RT-based bias-scores correlated with measures of chocolate craving. Results: Behaviorally, we found a highly reliable approach bias toward chocolate, defined by faster RTs in the compatible conditions (approach chocolate, avoid objects) compared to the incompatible conditions (avoid chocolate, approach objects). Neurally, this compatibility effect involved activity in the left medial OFC, a neural response that was positively correlated with individual approach bias scores. Conclusions: This study shows that the relevant feature AAT can be implemented in an fMRI setting in a supine position using buttons. An approach bias toward chocolate seems related to medial OFC activation that might serve to devalue chocolate when it has to be avoided. Our demonstration of neural and behavioral approach biases for chocolate underscores the need for stimulus-specific cognitive trainings to support healthy consumption and successful self-regulation.

Habituation or sensitization of brain response to food cues: Temporal dynamic analysis in an functional magnetic resonance imaging study

Introduction

In the modern obesogenic environment, heightened reactivity to food-associated cues plays a major role in overconsumption by evoking appetitive responses. Accordingly, functional magnetic resonance imaging (fMRI) studies have implicated regions of the salience and rewards processing in this dysfunctional food cue-reactivity, but the temporal dynamics of brain activation (sensitization or habituation over time) remain poorly understood.

Methods

Forty-nine obese or overweight adults were scanned in a single fMRI session to examine brain activation during the performance of a food cue-reactivity task. A general linear model (GLM) was used to validate the activation pattern of food cue reactivity in food > neutral contrast. The linear mixed effect models were used to examine the effect of time on the neuronal response during the paradigm of food cue reactivity. Neuro-behavioral relationships were investigated with Pearson's correlation tests and group factor analysis (GFA).

Results

A linear mixed-effect model revealed a trend for the time-by-condition interactions in the left medial amygdala [t(289) = 2.21, β = 0.1, P = 0.028], right lateral amygdala [t(289) = 2.01, β = 0.26, P = 0.045], right nucleus accumbens (NAc) [t(289) = 2.81, β = 0.13, P = 0.005] and left dorsolateral prefrontal cortex (DLPFC) [t(289) = 2.58, β = 0.14, P = 0.01], as well as in the left superior temporal cortex [42 Area: t(289) = 2.53, β = 0.15, P = 0.012; TE1.0_TE1.2 Area: t(289) = 3.13, β = 0.27, P = 0.002]. Habituation of blood-oxygenation-level-dependent (BOLD) signal during exposure to food vs. neutral stimuli was evident in these regions. We have not found any area in the brain with significant increased response to food-related cues over time (sensitization). Our results elucidate the temporal dynamics of cue-reactivity in overweight and obese individuals with food-induced craving. Both subcortical areas involved in reward processing and cortical areas involved in inhibitory processing are getting habituated over time in response to food vs. neutral cues. There were significant bivariate correlations between self-report behavioral/psychological measures with individual habituation slopes for the regions with dynamic activity, but no robust cross-unit latent factors were identified between the behavioral, demographic, and self-report psychological groups.

Discussion

This work provides novel insights into dynamic neural circuit mechanisms supporting food cue reactivity, thereby suggesting pathways in biomarker development and cue-desensitization interventions.

Utility of 'substance use disorder' as a heuristic for understanding overeating and obesity

Rates of obesity and obesity-associated diseases have increased dramatically in countries with developed economies. Substance use disorders (SUDs) are characterized by the persistent use of the substance despite negative consequences. It has been hypothesized that overconsumption of palatable energy dense food can elicit SUD-like maladaptive behaviors that contribute to persistent caloric intake beyond homeostatic need even in the face of negative consequences. Palatable food and drugs of abuse act on many of the same motivation-related circuits in the brain, and can induce, at least superficially, similar molecular, cellular, and physiological adaptations on these circuits. As such, applying knowledge about the neurobiological mechanisms of SUDs may serve as useful heuristic to better understand the persistent overconsumption of palatable food that contributes to obesity. However, many important differences exist between the actions of drugs of abuse and palatable food in the brain. This warrants caution when attributing weight gain and obesity to the manifestation of a putative SUD-related behavioral disorder. Here, we describe similarities and differences between compulsive drug use in SUDs and overconsumption in obesity and consider the merit of the concept of "food addiction".

A Neuroeconomics Approach to Obesity

Obesity is a heterogeneous condition that is affected by physiological, behavioral, and environmental factors. Value-based decision making is a useful framework for integrating these factors at the individual level. The disciplines of behavioral economics and reinforcement learning provide tools for identifying specific cognitive and motivational processes that may contribute to the development and maintenance of obesity. Neuroeconomics complements these disciplines by studying the neural mechanisms underlying these processes. We surveyed recent literature on individual decision characteristics that are most frequently implicated in obesity: discounting the value of future outcomes, attitudes toward uncertainty, and learning from rewards and punishments. Our survey highlighted both consistent and inconsistent behavioral findings. These findings underscore the need to examine multiple processes within individuals to identify unique behavioral profiles associated with obesity. Such individual characterization will inform future studies on the neurobiology of obesity as well as the design of effective interventions that are individually tailored.

Altered Brain Structural Reorganization and Hierarchical Integrated Processing in Obesity

The brain receives sensory information about food, evaluates its desirability and value, and responds with approach or withdrawal. The evaluation process of food in the brain with obesity may involve a variety of neurocircuit abnormalities in the integration of internal and external information processing. There is a lack of consistency of the results extant reported for aberrant changes in the brain with obesity that prohibits key brain alterations to be identified. Moreover, most studies focus on the observation of neural plasticity of function or structure, and the evidence for functional and structural correlations in the neuronal plasticity process of obesity is still insufficient. The aims of this article are to explore the key neural structural regions and the hierarchical activity pattern of key structural nodes and evaluate the correlation between changes in functional modulation and eating behavior. Forty-two participants with obesity and 33 normal-weight volunteers were recruited. Gray matter volume (GMV) and Granger causality analysis (GCA) were performed using the DPARSF, CAT12, and DynamicBC toolbox. Compared with the normal weight group, the obesity group exhibited significantly increased GMV in the left parahippocampal gyrus (PG). The obesity group showed decreased causal inflow to the left PG from the left orbitofrontal cortex (OFC), right calcarine, and bilateral supplementary motor area (SMA). Decreased causal outflow to the left OFC, right precuneus, and right SMA from the left PG, as well as increased causal outflow to the left middle occipital gyrus (MOG) were observed in the obesity group. Negative correlations were found between DEBQ-External scores and causal outflow from the left PG to the left OFC, and DEBQ-Restraint scores and causal inflow from the left OFC to the left PG in the obesity group. Positive correlation was found between DEBQ-External scores and causal outflow from the left PG to the left MOG. These results show that the increased GMV in the PG may play an important role in obesity, which may be related to devalued reward system, altered behavioral inhibition, and the disengagement of attentional and visual function for external signals. These findings have important implications for understanding neural mechanisms in obesity and developing individual-tailored strategies for obesity prevention.

Coexistence of sensory qualities and value representations in human orbitofrontal cortex

Despite the multiple regions and neural networks associated with value-based decision-making, the orbitofrontal cortex (OFC) is possible a particularly important one. Although the role of the OFC in reinforcer devaluation tasks, which assess the ability to represent identity, sensory qualities, and subjective values of the expected outcomes, has been established, the specific aspect represented in this area remains unclear. In this study, using functional magnetic resonance imaging, wherein participants rated the palatability of 128 food items using photographs, we investigated whether the human OFC represents object identity, sensory qualities, or value. Employing many items helped us dissociate object identity from sensory qualities and values; the inferred sensory qualities of identical items were manipulated by a change in metabolic state. Moreover, value differences between items were analytically controlled by employing a technique similar to age adjustment. The palatability ratings for food items significantly decreased after a meal. Using representational similarity analysis, we confirmed that the OFC represents value. Moreover, identical items were represented similarly in the lateral OFC in a given metabolic state; however, these representations were altered post-feeding. Importantly, this change was not explained by subjective value, suggesting that the OFC represents sensory quality and value, but not object identity.

The evidential value of research on cognitive training to change food-related biases and unhealthy eating behavior: A systematic review and p-curve analysis

Cognitive bias modification (CBM), which retrains implicit biases towards unhealthy foods, has been proposed as a promising adjunct to improve the efficacy of weight loss interventions. We conducted a systematic review of research on three CBM approaches (i.e., cue-specific inhibitory control, approach bias modification, and attentional bias modification) for reducing unhealthy eating biases and behavior. We performed a p-curve analysis to determine the evidential value of this research; this method is optimally suited to clarify whether published results reflect true effects or false positives due to publication and reporting biases. When considering all CBM approaches, our results suggested that the findings of CBM trials targeting unhealthy eating are unlikely to be false positives. However, only research on attentional bias modification reached acceptable levels of power. These results suggest that CBM interventions may be an effective strategy to enhance the efficacy of weight loss interventions. However, there is room for improvement in the methodological standards of this area of research, especially increasing the statistical power can help to fully clarify the clinical potential of CBM, and determine the role of potential moderators.

A dismantling study on imaginal retraining in overweight or obese women

Imaginal retraining is a variant of approach bias modification and transfers the method into one's own mind. As the technique contains multiple elements, this pilot study aimed to dismantle which of its components is most efficient in reducing craving for high-calorie food. A total of 113 women were randomly allocated to one out of six conditions containing a short intervention to mentally manipulate a picture displaying high-calorie foods. Four of the interventions involved different combinations of elements of the imaginal retraining technique, while the remaining two conditions comprised thought suppression or merely observing a picture. Participants rated their level of craving, as well as three pictures containing healthy and unhealthy foods regarding their pleasantness before and after the interventions took place. Within-group changes were assessed with paired t-tests (in case of non-normal data Wilcoxon paired t-tests) and between-group differences with one-way ANOVAs (non-parametric Kruskal-Wallis tests). A trend level reduction in craving was found in the imaginal retraining condition with and without a movement. A post hoc analysis of both conditions joint together showed a statistically significant reduction in craving. In addition, positive picture appraisal for unhealthy foods was significantly reduced in both imaginal retraining conditions (with and without movement) with medium to large effect sizes. This study demonstrated that imaginal retraining with an arm movement can reduce craving and picture appraisal for high-calorie foods significantly in a one-time application. It is a promising technique to reduce appraisal for unhealthy high-calorie foods. Future studies should repeat the experiment in situations of high craving and allow for a personalized selection of stimuli.

Is the habit system altered in individuals with obesity? A systematic review

Habit-like eating behavior is repeatedly pointed to as a key cognitive mechanism contributing to the emergence and maintenance of obesity. Here, we conducted a systematic review of the literature to assess the existent behavioral evidence for the Habit Hypothesis for Overeating (HHO) which states that obesity is the consequence of an imbalance between the habit and goal-directed reward learning systems, leading to overconsumption of food. We found a total of 19 studies implementing a variety of experimental protocols (i.e., free operant paradigm, slips-of-action test, two-step task, Pavlovian-to-Instrumental paradigm, probabilistic learning task) and manipulations. Taken together, the studies on clinical (binge eating disorder) and non-clinical individuals with overweight or obesity do not support the HHO conclusively. While the scientific literature on HHO is still in its infancy, the heterogeneity of the extant studies makes it difficult to evaluate the degree of convergence of these findings. Uncovering the role of reward learning systems in eating behaviors might have a transformative impact on public health.

Mind the food: behavioural characteristics and imaging signatures of the specific handling of food objects

In our world with nearly omnipresent availability of attractive and palatable high-calorie food, the struggle against overweight and obesity is a major individual and public health challenge. Preference for unhealthy food and eating-related habits have a strong influence on health, suggesting that high-calorie food triggers fast and near-automatic reaching and grasping movements. Therefore, it is important to better understand the specific neural mechanisms that control the handling of food involving a coordinated interplay between sensoric, motoric, and cognitive subsystems. To this end, 30 healthy participants (Ø BMI: 22.86 kg/m2; BMI range: 19-30 kg/m2; 23 females) were instructed to collect one of two concurrently presented objects (food vs. office tools) by manual movement in virtual reality (VR) and on a touchscreen. Parallel to the task in VR, regional brain activity was measured by functional near-infrared spectroscopy (fNIRS). In the VR and on the touchscreen, stimulus recognition and selection were faster for food than for office tools. Yet, food was collected more slowly than office tools when measured in VR. On the background of increased brain activity in the right dorsolateral prefrontal cortex (dlPFC) during food trials, this suggests more behavioural control activity during handling foods. In sum, this study emphasizes the role of the right dlPFC in faster recognition and selection of food as part of a food-valuation network, more controlled handling of food in the VR which highlights the relevance of medium for modelling food-specific embodied cognitions.

The impact of overweight/obesity on monetary reward processing: A systematic review

OBJECTIVE

Converging evidence suggests abnormalities in monetary reward processing may underlie the shared pathophysiology between major depressive disorder and obesity. As such, there is a need to parse deficits in specific subcomponents of monetary reward functioning (i.e., valuation, learning and anticipation).

METHODS

PsycINFO, Google Scholar and PubMed databases were searched for English-language articles published between database inception to June 6th, 2020. Studies were identified using the following medical search heading (MeSH) terms and search strings: (reward (valuation OR motivation OR anticipation OR learning OR functioning OR decision-making OR reinforcement)) AND ((obesity OR overweight OR obese).

RESULTS

Findings were reviewed from 11 studies evaluating the association between obesity and monetary reward processing. Four studies found significant differences in reward learning in individuals with obesity compared to normal-weight participants. Five studies found body mass index (BMI) to be predictive of willingness to expend effort (i.e., valuation) for a monetary reward. Three studies found changes in neural activations in the ventral striatum during anticipatory phases preceding receipt of a monetary reward in participants with obesity.

CONCLUSIONS

Participants with obesity demonstrated significantly poorer performance in task-based measures of reward learning, valuation, and anticipation, resulting in lower monetary reward outcomes across all studies compared to healthy controls. Notably, participants with obesity and comorbid depression performed worse than participants with no comorbid depression.

LIMITATIONS

There persists heterogeneity between studies with regards to inclusion of mood disorder populations and exclusion of psychiatric comorbidities in groups with obesity.

Selective Devaluation Affects the Processing of Preferred Rewards

The present study investigated whether the representation of subjective preferences in the event-related potential is manipulable through selective devaluation, i.e., the consumption of a specific food item until satiety. Thirty-four participants completed a gambling task in which they chose between virtual doors to find one of three snack items, representing a high, medium, or low preference outcome as defined by individual desire-to-eat ratings. In one of two test sessions, they underwent selective devaluation of the high preference outcome. In the other, they completed the task on an empty stomach. Consistent with previous findings, averaged across sessions, amplitudes were increased for more preferred rewards in the time windows of P2, late FRN, and P300. As hypothesised, we also found a selective devaluation effect for the high preference outcome in the P300 time window, reflected in a decrease in amplitude. The present results provide evidence for modulations of reward processing not only by individual factors, such as subjective preferences, but also by the current motivational state. Importantly, the present data suggest that selective devaluation effects in the P300 may be a promising tool to further characterise altered valuation of food rewards in the context of eating disorders and obesity.

A Systematic Review of Obesity and Binge Eating Associated Impairment of the Cognitive Inhibition System

Altered functioning of the inhibition system and the resulting higher impulsivity are known to play a major role in overeating. Considering the great impact of disinhibited eating behavior on obesity onset and maintenance, this systematic review of the literature aims at identifying to what extent the brain inhibitory networks are impaired in individuals with obesity. It also aims at examining whether the presence of binge eating disorder leads to similar although steeper neural deterioration. We identified 12 studies that specifically assessed impulsivity during neuroimaging. We found a significant alteration of neural circuits primarily involving the frontal and limbic regions. Functional activity results show BMI-dependent hypoactivity of frontal regions during cognitive inhibition and either increased or decreased patterns of activity in several other brain regions, according to their respective role in inhibition processes. The presence of binge eating disorder results in further aggravation of those neural alterations. Connectivity results mainly report strengthened connectivity patterns across frontal, parietal, and limbic networks. Neuroimaging studies suggest significant impairment of various neural circuits involved in inhibition processes in individuals with obesity. The elaboration of accurate therapeutic neurocognitive interventions, however, requires further investigations, for a deeper identification and understanding of obesity-related alterations of the inhibition brain system.

Sensory cue reactivity: Sensitization in alcohol use disorder and obesity

Neuroimaging techniques to measure the function of the human brain such as electroencephalography (EEG), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI), are powerful tools for understanding the underlying neural circuitry associated with alcohol use disorder (AUD) and obesity. The sensory (visual, taste and smell) paradigms used in neuroimaging studies represent an ideal platform to investigate the connection between the different neural circuits subserving the reward/executive control systems in these disorders, which may offer a translational mechanism for novel intervention predictions. Thus, the current review provides an integrated summary of the recent neuroimaging studies that have applied cue-reactivity paradigms and neuromodulation strategies to explore underlying alterations in neural circuitry as well in treatment strategies in AUD and obesity. Finally, we discuss literature on mechanisms associated with increased alcohol sensitivity post-bariatric surgery (BS) which offers guidance for future research to use sensory percepts in elucidating the relation of reward signaling in AUD development post-BS.

Reliance on model-based and model-free control in obesity

Consuming more energy than is expended may reflect a failure of control over eating behaviour in obesity. Behavioural control arises from a balance between two dissociable strategies of reinforcement learning: model-free and model-based. We hypothesized that weight status relates to an imbalance in reliance on model-based and model-free control, and that it may do so in a linear or quadratic manner. To test this, 90 healthy participants in a wide BMI range [normal-weight (n = 31), overweight (n = 29), obese (n = 30)] performed a sequential decision-making task. The primary analysis indicated that obese participants relied less on model-based control than overweight and normal-weight participants, with no difference between overweight and normal-weight participants. In line, secondary continuous analyses revealed a negative linear, but not quadratic, relationship between BMI and model-based control. Computational modelling of choice behaviour suggested that a mixture of both strategies was shifted towards less model-based control in obese participants. Our findings suggest that obesity may indeed be related to an imbalance in behavioural control as expressed in a phenotype of less model-based control potentially resulting from enhanced reliance on model-free computations.

Preliminary evidence for an association between intake of high-fat high-sugar diet, variations in peripheral dopamine precursor availability and dopamine-dependent cognition in humans

Obesity is associated with alterations in dopaminergic transmission and cognitive function. Rodent studies suggest that diets rich in saturated fat and refined sugars (HFS), as opposed to diets diets low in saturated fat and refined sugars (LFS), change the dopamine system independent of excessive body weight. However, 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 task performance between two groups differing in habitual intake of dietary fat and sugar. Specifically, we used a double-blind within-subject cross-over design to compare the effect of acute phenylalanine/tyrosine depletion 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 matched for body mass index (mostly normal weight to overweight) and IQ. Depletion of peripheral precursors of dopamine reduced the working memory specific performance on the operation span task in the LFS, but not in the HFS group (P = 0.016). Learning from positive- and negative-reinforcement (probabilistic selection task) was increased in both diet groups after dopamine depletion (P = 0.049). As a 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 = 0.025). Our data provide the first evidence indicating that the intake of HFS is associated with changes in dopamine precursor availability, which is suggestive of changes in central dopamine levels in humans. The observed associations are present in a sample of normal to overweight participants (ie, in the absence of obesity), suggesting that the consumption of a HFS might already be associated with altered behaviours. Alternatively, the effects of HFS diet and obesity might be independent.

Relating goal-directed behaviour to grazing in persons with obesity with and without eating disorder features

BACKGROUND

Both obesity and eating disorders (ED) have been associated with reductions in purposeful, flexible goal-directed behaviour, and with an overreliance on more rigid habitual behaviour. It is currently unknown whether grazing, an eating style which is common in both conditions, is related to goal-directed behaviour. The current study therefore aimed to relate grazing to goal-directed behaviour in a group of participants with obesity with and without ED features, compared to a healthy-weight control group.

METHODS

Participants (N = 87; 67.8% women, mean age 28.57 years), of whom 19 had obesity and significant eating disorder features, 25 had obesity but without marked eating disorder features, and 43 were age- and sex-matched healthy-weight controls, completed two instrumental learning tasks assessing action-outcome contingency sensitivity and devaluation sensitivity, as well as demographic and eating disorder-related questionnaires. Gamma and Ordinary Least Squares regressions were performed to examine the effect of group and grazing on goal-directed behaviour.

RESULTS

Lower action-outcome contingency sensitivity was found in the group with obesity and with eating disorder features than in the group with obesity but without eating disorder features or in healthy controls. No group differences in devaluation sensitivity were found. A small but significant relationship was found between grazing severity and contingency sensitivity in the group with obesity and eating disorder features, such that increasing grazing severity was associated with less diminished contingency sensitivity.

CONCLUSIONS

There is some indication that in persons with obesity and eating disorder features instrumental behaviour is less flexible and adaptive; furthermore, within this group grazing may represent a goal-directed behaviour, despite unhelpful long-term implications of grazing.

Linking Grazing to Inhibition and Goal-Directed Behaviour in Obesity With and Without Eating Disorder Features

Recent models of obesity and eating behaviour have implicated both automatic responding to food-related cues and executive functioning in driving dietary choice. This study aimed to relate grazing severity to high weight with and without significant eating disorder features via the effects of inhibition and degree of goal-directed behaviour, in persons with obesity with and without significant eating disorder features compared to healthy controls. Forty-four participants with obesity (43.1% endorsing marked eating disorder features), and 43 healthy-weight age- and sex-matched participants (N = 87; 67.8% female, age = 28.57 (8.70; 18.18–58.34) years, BMI = 29.18 (7.80; 18.65–51.95) kg/m2) completed demographic and eating disorder-related questionnaires, a neuropsychological task of inhibition and an instrumental decision-making task. Bootstrapped serial mediation analyses were performed to examine the effect of group on grazing via goal-directed behaviour and inhibition. While significant differences existed between the groups in terms of inhibition, goal-directed behaviour and grazing severity, the effect of group on grazing severity was not found to be mediated by the degree of behavioural goal-directedness and inhibition. Therefore, :in persons with obesity with or without eating disorder symptoms, putative relationships between a reduced inhibitory profile and/or behaviour that is less flexible and goal-directed and eating behaviours such as grazing, remain unclear.

What Should I Eat and Why? The Environmental, Genetic, and Behavioral Determinants of Food Choice: Summary from a Pennington Scientific Symposium

This review details the proceedings of a Pennington Biomedical scientific symposium titled, "What Should I Eat and Why? The Environmental, Genetic, and Behavioral Determinants of Food Choice." The symposium was designed to review the literature about energy homeostasis, particularly related to food choice and feeding behaviors, from psychology to physiology. This review discusses the intrinsic determinants of food choice, including biological mechanisms (genetics), peripheral and central signals, brain correlates, and the potential role of the microbiome. This review also address the extrinsic determinants (environment) of food choice within our physical and social environments. Finally, this review reports the current treatment practices for the clinical management of eating-induced overweight and obesity. An improved understanding of these determinants will inform best practices for the clinical treatment and prevention of obesity. Strategies paired with systemic shifts in our public health policies and changes in our "obesogenic" environment will be most effective at attenuating the obesity epidemic.

Abnormal Regional Neural Activity and Reorganized Neural Network in Obesity: Evidence from Resting-State fMRI

OBJECTIVE

This study aimed to investigate regional neural activity and regulation of patterns in the reorganized neural network of obesity and explore the correlation between brain activities and eating behavior.

METHODS

A total of 23 individuals with obesity and 23 controls with normal weight were enrolled. Functional magnetic resonance imaging (fMRI) data were acquired using 3.0-T MRI. Amplitude of low-frequency fluctuation and functional connectivity (FC) analyses were conducted using Data Processing Assistant for resting-state fMRI and Resting-State fMRI Data Analysis Toolkit (REST).

RESULTS

The group with obesity showed increased amplitude of low-frequency values in left fusiform gyrus/amygdala, inferior temporal gyrus (ITG), hippocampus/parahippocampal gyrus, and bilateral caudate but decreased values in right superior temporal gyrus. The group with obesity showed increased FC between left caudate and right superior temporal gyrus, left fusiform gyrus/amygdala and left ITG, right caudate and left fusiform gyrus/amygdala, and right caudate and left hippocampus/parahippocampal gyrus. Dutch Eating Behavior Questionnaire-Emotional scores were positively correlated with FC between left hippocampus/parahippocampal gyrus and right caudate but negatively correlated with FC between left fusiform gyrus/amygdala and left ITG.

CONCLUSIONS

The study indicated the reorganized neural network presented as a bilateral cross-regulation pattern across hemispheres between reward and various appetite-related functional processing, thus affecting emotional and external eating behavior. These results could provide further evidence for neuropsychological underpinnings of food intake and their neuromodulatory therapeutic potential in obesity.

Enhanced Go and NoGo Learning in Individuals With Obesity

Overeating in individuals with obesity is hypothesized to be partly caused by automatic action tendencies to food cues that have the potential to override goal-directed dietary restriction. Individuals with obesity are often characterized by alterations in the processing of such rewarding food, but also of non-food stimuli, and previous research has suggested a stronger impact on the execution of goal-directed actions in obesity. Here, we investigated whether Pavlovian cues can also corrupt the learning of new approach or withdrawal behavior in individuals with obesity. We employed a probabilistic Pavlovian-instrumental learning paradigm in which participants (29 normal-weight and 29 obese) learned to actively respond (Go learning) or withhold a response (NoGo learning) in order to gain monetary rewards or avoid losses. Participants were better at learning active approach responses (Go) in the light of anticipated rewards and at learning to withhold a response (NoGo) in the light of imminent punishments. Importantly, there was no evidence for a stronger corruption of instrumental learning in individuals with obesity. Instead, they showed better learning across conditions than normal-weight participants. Using a computational reinforcement learning model, we additionally found an increased learning rate in individuals with obesity. Previous studies have mostly reported a lower reinforcement learning performance in individuals with obesity. Our results contradict this and suggest that their performance is not universally impaired: Instead, while previous studies found reduced stimulus-value learning, individuals with obesity may show better action-value learning. Our findings highlight the need for a broader investigation of behavioral adaptation in obesity across different task designs and types of reinforcement learning.

Study protocol of a randomised controlled feasibility study of food-related computerised attention training versus mindfulness training and waiting-list control for adults with overweight or obesity

Background

Obesity is a highly prevalent condition with multiple adverse health consequences. Widely available first-line treatments for obesity, such as dietary and other lifestyle interventions, typically have only short-term effects. Thus, new treatment approaches are needed. Novel interventions such as Attention Bias Modification Training (ABMT) and mindfulness-based interventions focus on modifying different maladaptive cognitive patterns typically present in people with obesity (e.g. attention bias to food cues); however, their mechanisms of action remain largely unknown. We describe the theoretical basis and the rationale for a study protocol of a feasibility randomised controlled trial (RCT) comparing two attention trainings (ABMT vs Mindfulness Training [MT]) in people with overweight or obesity. The aim of this study is to inform the development of a large-scale RCT in relation to acceptability and attendance rates and to identify preliminary evidence for the interventions’ clinical efficacy and potential underlying mechanisms.

Design

Forty-five adults who are either overweight or obese (minimum body mass index of 25 kg/m²) will be randomly allocated to receive eight sessions over eight weeks of either computerised ABMT or MT or be on a waiting list. Clinical and cognitive outcomes will be assessed at baseline, post-treatment (8 weeks) and follow-up (12 weeks post-randomisation). These include mood, body composition and attention biases. Credibility and acceptability of the trainings will be assessed using questionnaires, and recruitment and retention rates will be recorded.

Discussion

Findings will inform the feasibility of developing a large-scale RCT that takes into consideration effect sizes for primary outcome measures and the acceptability of the design. The study will also provide preliminary evidence on the clinical efficacy of two different attention trainings for people with obesity and associated underlying mechanisms.

Trial registration

ISRCTN Registry, ISRCTN15745838. Registered on 22 May 2018. 

Erratum: The Cognitive Drivers of Compulsive Eating Behavior

[This corrects the article DOI: 10.3389/fnbeh.2018.00338.].

Neuroendocrinological mechanisms underlying impulsive and compulsive behaviors in obesity: a narrative review of fMRI studies

Impulsivity and compulsivity are multidimensional constructs that are increasingly considered determinants of obesity. Studies using functional magnetic resonance imaging (fMRI) have provided insight on how differences in brain response during tasks exploring facets of impulsivity and compulsivity relate to the ingestive behaviors that support the etiology and maintenance of obesity. In this narrative review, we provide an overview of neuroimaging studies exploring impulsivity and compulsivity factors as they relate to weight status. Special focus will be placed on studies examining the impulsivity-related dimensions of attentional bias, delayed gratification and emotion regulation. Discussions of compulsivity within the context of obesity will be restricted to fMRI studies investigating habit formation and response flexibility under shifting contingencies. Further, we will highlight neuroimaging research demonstrating how alterations in neuroendocrine functioning are linked to excessive food intake and may serve as a driver of the impulsive and compulsive behaviors observed in obesity. Research on the associations between brain response with neuroendocrine factors, such as insulin, peptide YY (PYY), leptin, ghrelin and glucagon-like peptide 1 (GLP-1), will be reviewed.

Decreased Conflict Control in Overweight Chinese Females: Behavioral and Event-Related Potentials Evidence

Overweight or obesity is related to a decrease in cognitive control, especially conflict control. However, research on conflict control in overweight/obese individuals are still controversial. This study was conducted to explore general and food-related conflict control in overweight Chinese females (OWs) with a color–word Stroop task and a food-related conflict task. Event-related potentials (ERPs) were recorded during the food-related conflict task. Behavioral results showed that, OWs had a longer reaction time (RT) than normal-weight Chinese females (NWs), in both tasks. ERP results in the food-related conflict task showed that there was a reduction of N2 and N450 response strength in OWs, and the P3 and late positive component (LPC) response strength was enhanced. Results indicated that OWs might be less efficient in monitoring and resolving conflict, and OWs tended to have a higher motivational or emotional involvement in processing food-related stimuli, which was likely to contribute to their difficulty in losing weight.

Characterization of Industry 4.0 Lean Management Problem-Solving Behavioral Patterns Using EEG Sensors and Deep Learning

Industry 4.0 leaders solve problems all of the time. Successful problem-solving behavioral pattern choice determines organizational and personal success, therefore a proper understanding of the problem-solving-related neurological dynamics is sure to help increase business performance. The purpose of this paper is two-fold: first, to discover relevant neurological characteristics of problem-solving behavioral patterns, and second, to conduct a characterization of two problem-solving behavioral patterns with the aid of deep-learning architectures. This is done by combining electroencephalographic non-invasive sensors that capture process owners' brain activity signals and a deep-learning soft sensor that performs an accurate characterization of such signals with an accuracy rate of over 99% in the presented case-study dataset. As a result, the deep-learning characterization of lean management (LM) problem-solving behavioral patterns is expected to help Industry 4.0 leaders in their choice of adequate manufacturing systems and their related problem-solving methods in their future pursuit of strategic organizational goals.

Appetitive Pavlovian-to-Instrumental Transfer in Participants with Normal-Weight and Obesity

Altered eating behavior due to modern, food-enriched environments has a share in the recent obesity upsurge, though the exact mechanisms remain unclear. This study aims to assess whether higher weight or weight gain are related to stronger effects of external cues on motivation-driven behavior. 51 people with and without obesity completed an appetitive Pavlovian-to-Instrumental Transfer (PIT) paradigm. During training, button presses as well as presentation of fractal images resulted in three palatable and one neutral taste outcome. In the subsequent test phase, outcome-specific and general behavioral bias of the positively associated fractal images on deliberate button press were tested under extinction. While all participants showed signs of specific transfer, general transfer was not elicited. Contrary to our expectations, there was no main effect of weight group on PIT magnitude. Participants with obesity exhibited higher scores in the Three-Factor Eating Questionnaire Disinhibition scale, replicating a very robust effect from previous literature. Individual Restraint scores were able to predict body-mass index (BMI) change after a three-year period. Our data indicate that PIT is an important player in how our environment influences the initiation of food intake, but its effects alone cannot explain differences in-or future development of-individual weight.

The Cognitive Drivers of Compulsive Eating Behavior

Compulsivity is a central feature of obsessive-compulsive and addictive disorders, which share considerable overlap with excessive eating in terms of repetitive behavior despite negative consequences. Excessive eating behavior is characteristic of several eating-related conditions, including eating disorders [bulimia nervosa (BN), binge eating disorder (BED)], obesity, and food addiction (FA). Compulsivity is proposed to be driven by four distinct cognitive components, namely, contingency-related cognitive flexibility, task/attentional set-shifting, attentional bias/disengagement and habit learning. However, it is unclear whether repetitive behavior in eating-related conditions is underpinned by deficits in these cognitive components. The current mini-review synthesizes the available evidence for performance on compulsivity-related cognitive tasks for each cognitive domain among populations with excessive eating behavior. In three of the four cognitive domains, i.e., set-shifting, attentional bias and habit learning, findings were mixed. Evidence more strongly pointed towards impaired contingency-related cognitive flexibility only in obesity and attentional bias/disengagement deficits only in obesity and BED. Overall, the findings of the reviewed studies support the idea that compulsivity-related cognitive deficits are common across a spectrum of eating-related conditions, although evidence was inconsistent or lacking for some disorders. We discuss the theoretical and practical importance of these results, and their implications for our understanding of compulsivity in eating-related conditions.

Dorsolateral and medial prefrontal cortex mediate the influence of incidental priming on economic decision making in obesity

Obese individuals discount future rewards to a higher degree than lean individuals, which is generally considered disadvantageous. Moreover, their decisions are altered more easily by decision-irrelevant cues. Here, we investigated neural correlates of this phenomenon using functional MRI. We tested 30 lean and 26 obese human subjects on a primed delay discounting paradigm using gustatory and visual cues of positive, neutral and negative valence to bias their intertemporal preferences. We hypothesised that activation differences in reward-related and behavioural control areas, and changes in connectivity between these areas, would reflect the effect of these cues. Here, obese subjects were more susceptible to priming with negative gustatory cues towards delayed choices as opposed to lean subjects. This was related to lower activity in the left dorsolateral prefrontal cortex during priming. Modulation of functional connectivity between the dlPFC and the ventromedial PFC by the behavioural priming effect correlated negatively with BMI. This might indicate that default goals of obese individuals were different from those of lean participants, as the dlPFC has been suggested to be involved in internal goal pursuit. The present results further our understanding of the role of the PFC in decision-making and might inform future weight-management approaches based on non-invasive brain stimulation.

Enhanced food-related responses in the ventral medial prefrontal cortex in narcolepsy type 1

Narcolepsy type 1 is a chronic sleep disorder caused by a deficiency of the orexin (hypocretin) neuropeptides. In addition to sleep regulation, orexin is important for motivated control processes. Weight gain and obesity are common in narcolepsy. However, the neurocognitive processes associated with food-related control and overeating in narcolepsy are unknown. We explored the neural correlates of general and food-related attentional control in narcolepsy-type-1 patients (n = 23) and healthy BMI-matched controls (n = 20). We measured attentional bias to food words with a Food Stroop task and general executive control with a Classic Stroop task during fMRI. Moreover, using multiple linear regression, we assessed the relative contribution of neural responses during Food Stroop and Classic Stroop to spontaneous snack intake. Relative to healthy controls, narcolepsy patients showed enhanced ventral medial prefrontal cortex responses and connectivity with motor cortex during the Food Stroop task, but attenuated dorsal medial prefrontal cortex responses during the Classic Stroop task. Moreover, the former activity but not the latter, was a significant predictor of spontaneous snack intake. These findings demonstrate that narcolepsy, characterized by orexin deficiency, is associated with decreased dorsal medial prefrontal cortex responses during general executive control and enhanced ventral medial prefrontal cortex responses during food-driven attention.

Stress-induced reliance on habitual behavior is moderated by cortisol reactivity

Instrumental learning, i.e., learning that specific behaviors lead to desired outcomes, occurs through goal-directed and habit memory systems. Exposure to acute stress has been shown to result in less goal-directed control, thus rendering behavior more habitual. The aim of the current studies was to replicate and extend findings on stress-induced prompting of habitual responding and specifically focused on the role of stress-induced cortisol reactivity. Study 1 used an established outcome devaluation paradigm to assess goal-directed and habitual control. Study 2 utilized a modified version of this paradigm that was intended to establish stronger habitual responding through more extensive reward training and applying a relevant behavioral devaluation procedure (i.e., eating to satiety). Both studies failed to replicate that stress overall, i.e., independent of cortisol reactivity, shifted behavior from goal-directed to habitual control. However, both studies found that relative to stress-exposed cortisol non-responders and no-stress controls, participants displaying stress-induced cortisol reactivity displayed prominent habitual responding. These findings highlight the importance of stress-induced cortisol reactivity in facilitating habits.

Greater mindful eating practice is associated with better reversal learning

Mindfulness-based interventions are thought to reduce compulsive behavior such as overeating by promoting behavioral flexibility. Here the main aim was to provide support for mindfulness-mediated improvements in reversal learning, a direct measure of behavioral flexibility. We investigated whether an 8-week mindful eating intervention improved outcome-based reversal learning relative to an educational cooking (i.e., active control) intervention in a non-clinical population. Sixty-five healthy participants with a wide BMI range (19–35 kg/m²), who were motivated to change their eating habits, performed a deterministic reversal learning task that enabled the investigation of reward- and punishment-based reversal learning at baseline and following the intervention. No group differences in reversal learning were observed. However, time invested in the mindful eating, but not the educational cooking intervention correlated positively with changes in reversal learning, in a manner independent of outcome valence. These findings suggest that greater amount of mindfulness practice can lead to increased behavioral flexibility, which, in turn, might help overcome compulsive eating in clinical populations.

Allostatic Load Is Linked to Cortical Thickness Changes Depending on Body-Weight Status

Objective: Overweight (body mass index or BMI ≥ 25 kg/m²) and stress interact with each other in complex ways. Overweight promotes chronic low-inflammation states, while stress is known to mediate caloric intake. Both conditions are linked to several avoidable health problems and to cognitive decline, brain atrophy, and dementia. Since it was proposed as a framework for the onset of mental illness, the allostatic load model has received increasing attention. Although changes in health and cognition related to overweight and stress are well-documented separately, the association between allostatic load and brain integrity has not been addressed in depth, especially among overweight subjects.

Method: Thirty-four healthy overweight-to-obese and 29 lean adults underwent blood testing, neuropsychological examination, and magnetic resonance imaging to assess the relationship between cortical thickness and allostatic load, represented as an index of 15 biomarkers (this is, systolic and diastolic arterial tension, glycated hemoglobin, glucose, creatinine, total cholesterol, HDL and LDL cholesterol, triglycerides, c-reactive protein, interleukin-6, insulin, cortisol, fibrinogen, and leptin).

Results: Allostatic load indexes showed widespread positive and negative significant correlations (p < 0.01) with cortical thickness values depending on body-weight status.

Conclusion: The increase of allostatic load is linked to changes in the gray matter composition of regions monitoring behavior, sensory-reward processing, and general cognitive function.