Regional cerebral blood flow during exposure to food in obese binge eating women

Pupillary dilation response to the auditory food words in adolescents with obesity without binge eating disorder

Childhood obesity is a growing global public health problem. Studies suggest that environmental cues contribute to developing and maintaining obesity. We aimed to evaluate pupillary changes to auditory food words vs. nonfood words and to conduct a dynamic temporal analysis of pupil size changes in adolescents with obesity without binge eating disorder by comparing healthy-weight adolescents. In this study, a total of 63 adolescents aged 12-18 years (n = 32, obesity group (OG); n = 31, control group (CG)) were included. In an auditory paradigm, participants were presented with a series of high and low-calorie food and nonfood words. A binocular remote eye-tracking device was used to measure pupil diameter. Generalized additive mixed models (GAMMs) were used for dynamic temporal analysis of pupillometry data. The results of GAMM analysis indicated that CG had larger pupil dilation than the OG while listening to auditory food words. CG had larger pupil dilation in food words than in nonfood words. However, the OG had a similar pupillary response in food and nonfood words. Pupil dilation response to higher-calorie foods was extended over the later stages of the time period (after 2000 ms) in the OG. In summary, our findings indicated that individuals with obesity had lower pupil dilation to auditory food words compared to normal-weight peers. Adolescents with obesity had prolonged pupillary dilation in higher calories of food words. The individual psychological factors affecting the dynamic changes of pupil responses to food cues in adolescents with obesity should be examined in further studies.

No effect of prefrontal transcranial direct current stimulation (tDCS) on food craving, food reward and subjective appetite in females displaying mild-to-moderate binge-type behaviour

Previous work suggests there may be an effect of transcranial direct current stimulation (tDCS) on appetite control in people at risk of overconsumption, however findings are inconsistent. This study aimed to further understand the potential eating behaviour trait-dependent effect of tDCS, specifically in those with binge-type behaviour. Seventeen females (23 ± 7 years, 25.4 ± 3.8 kg m-2) with mild-to-moderate binge eating behaviour completed two sessions of double-blind, randomised and counterbalanced anodal and sham tDCS applied over the right dorsolateral prefrontal cortex at 2.0 mA for 20 min. Subjective appetite visual analogue scales (VAS), the Food Craving Questionnaire-State (FCQ-S), and Leeds Food Preference Questionnaire (LFPQ) were completed pre- and post-tDCS. Participants then consumed a fixed-energy meal, followed by the VAS, FCQ-S and LFPQ. No difference between pre- and post-tDCS scores were found across fullness (p = 0.275, BF10 = 0.040), prospective consumption (p = 0.127, BF10 = 0.063), desire to eat (p = 0.247, BF10 = 0.054) or FCQ-S measures (p = 0.918, BF10 = 0.040) when comparing active and sham protocols. Only explicit liking and wanting for high-fat sweet foods were significantly different between conditions, with increased scores following active tDCS. When controlling for baseline hunger, the significant differences were removed (p = 0.138 to 0.161, BF10 = 0.810 to 1.074). The present data does not support the eating behaviour trait dependency of tDCS in a specific cohort of female participants with mild-to-moderate binge eating scores, and results align with those from individuals with healthy trait scores. This suggests participants with sub-clinical binge eating behaviour do not respond to tDCS. Future work should further explore effects in clinical and sub-clinical populations displaying susceptibility to overconsumption and weight gain.

Cerebral Blood Flow Alterations and Obesity: A Systematic Review and Meta-Analysis

Background: Reduction in cerebral blood flow (CBF) plays an essential role in the cognitive impairment and dementia in obesity. However, current conclusions regarding CBF changes in patients with obesity are inconsistent. Objective: A systematic review and meta-analysis was performed to evaluate the relationship between obesity and CBF alterations. Methods: We systematically screened published cross-sectional and longitudinal studies focusing on the differences in CBF between obese and normal-weight individuals. Eighteen studies including 24,866 participants, of which seven articles reported longitudinal results, were evaluated in the present study. Results: The results of the meta-analysis showed that in cross-sectional studies, body mass index (BMI) was negatively associated with CBF (β= –0.31, 95% confidence interval [CI]: –0.44, –0.19). Moreover, this systematic review demonstrated that obese individuals showed global and regional reductions in the CBF and increased CBF in diverse functional areas of the frontal lobe, including the prefrontal cortex, left frontal superior orbital, right frontal mid-orbital cortex, and left premotor superior frontal gyrus. Conclusion: Our findings suggest that BMI, rather than waist circumference and waist-to-hip ratio, is inversely associated with CBF in cross-sectional studies. The CBF of obese individuals showed global and regional reductions, including the frontal lobe, temporal and parietal lobes, cerebellum, hippocampus, and thalamus.

Brain regulation of hunger and motivation: The case for integrating homeostatic and hedonic concepts and its implications for obesity and addiction

Obesity and other eating disorders are marked by dysregulations to brain metabolic, hedonic, motivational, and sensory systems that control food intake. Classic approaches in hunger research have distinguished between hedonic and homeostatic processes, and have mostly treated these systems as independent. Hindbrain structures and a complex network of interconnected hypothalamic nuclei control metabolic processes, energy expenditure, and food intake while mesocorticolimbic structures are though to control hedonic and motivational processes associated with food reward. However, it is becoming increasingly clear that hedonic and homeostatic brain systems do not function in isolation, but rather interact as part of a larger network that regulates food intake. Incentive theories of motivation provide a useful route to explore these interactions. Adapting incentive theories of motivation can enable researchers to better how motivational systems dysfunction during disease. Obesity and addiction are associated with profound alterations to both hedonic and homeostatic brain systems that result in maladaptive patterns of consumption. A subset of individuals with obesity may experience pathological cravings for food due to incentive sensitization of brain systems that generate excessive 'wanting' to eat. Further progress in understanding how the brain regulates hunger and appetite may depend on merging traditional hedonic and homeostatic concepts of food reward and motivation.

Modulating eating behavior with transcranial direct current stimulation (tDCS): A systematic literature review on the impact of eating behavior traits

Transcranial direct current stimulation (tDCS) is becoming an increasingly popular technique for altering eating behaviors. Recent research suggests a possible eating behavior trait-dependent effect of tDCS. However, studies recruit participant populations with heterogeneous trait characteristics, including "healthy" individuals who do not present with eating behavior traits suggesting susceptibility to overconsumption. The present review considers the effects of tDCS across eating-related measures and explores whether a trait-dependent effect is evident across the literature. A literature search identified 28 articles using sham-controlled tDCS to modify eating-related measures. Random effects meta-analyses were performed, with subgroup analyses to identify differences between "healthy" and trait groups. Trivial overall effects (g = -0.12 to 0.09) of active versus sham tDCS were found. Subgroup analyses showed a more consistent effect for trait groups, with small and moderate effect size (g = -1.03 to 0.60), suggesting tDCS is dependent on participants' eating behavior traits. Larger effect sizes were found for those displaying traits associated with study outcomes (e.g., heightened food cravings). "Healthy" individuals appear to be unresponsive to stimulation. Based on this meta data, future work should recruit those with eating behavior trait susceptibilities to overconsumption, focusing on those who present with traits associated with the outcome of interest.

Altered regional grey matter volume and appetite-related hormone levels in adolescent obesity with or without binge-eating disorder

PURPOSE

Binge eating disorder (BED) is characterized by frequent and persistent overeating episodes of binge eating without compensatory behaviors. The aim was to evaluate regional gray matter volume (GMV) abnormalities and appetite-regulating hormone levels (NPY and Leptin) in obese subjects either with or without BED compared to healthy controls (HC).

METHODS

Twenty-six obese patients with BED, 25 obese patients without BED and 27 healthy subjects as an age-matched control group with neuroimaging and appetite-regulating hormone levels were found eligible for regional GMV abnormalities. A structural magnetic resonance scan and timely blood samples were drawn to assess the appetite-regulating hormone levels.

RESULTS

The BED obese patients had a greater GMVs of the right medial orbitofrontal cortex (OFC) and the left medial OFC compared to the non-BED obese patients. BED patients were characterized by greater GMV of the left medial OFC than HCs. Relative to the HCs, higher serum NPY levels were found in BED obese and non-BED obese groups. Serum leptin levels (pg/mL) had positively correlations with GMV in right medial OFC, left medial OFC, right lateral OFC, and left anterior cingulate cortex.

CONCLUSION

Among the reward processing network, which is largely associated with feeding behaviours in individuals with obesity and binge eating disorder, the OFC volumes was correlated with serum leptin concentrations. The results of our study may provide a rationale for exploring the link between regional grey matter volumes and appetite-related hormone levels in people with BED.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

Neuronal activities during palatable food consumption in the reward system of binge-like eating female rats

Binge eating disorder (BED), characterized by bingeing episodes and compulsivity, is the most prevalent eating disorder; however, little is known about its neurobiological underpinnings. In humans, BED is associated with desensitization of the reward system, specifically, the medial prefrontal cortex (mPFC), nucleus accumbens (Acb), and ventral tegmental area (VTA). Additionally, BED patients feel relieved during bingeing, suggesting that bingeing helps to decrease the negative emotions they were feeling prior to the binge episode. However, the mechanisms that underlie this feeling of relief in BED patients have not been well investigated. To investigate neuronal activity before and during palatable food consumption in BED, we performed in vivo electrophysiological recordings in a binge-like eating rat model (bingeing, n = 12 and non-bingeing, n = 14) and analyzed the firing rate of neurons in the mPFC, Acb, and VTA before and during access to sucrose solution. We also investigated changes in the firing rate of neurons in these regions during and between active bingeing, which may underlie the feeling of relief in BED patients. We found that neuronal firing rates of mPFC and VTA neurons in bingeing rats were lower than those in non-bingeing rats before and during sucrose consumption. Palatable food consumption increased neuronal firing rates during and between active bingeing in bingeing rats. Our results suggest a desynchronization in the activity of reward system regions, specifically in the mPFC, in bingeing rats, which may also contribute to BED. These results are consistent with those of functional magnetic resonance imaging (fMRI) studies that reported decreased activity in the reward system in BED patients. We propose that increased neuronal activity in the mPFC, Acb, or VTA produces an antidepressant effect in rats, which may underlie the sense of relief patients express during bingeing episodes.

Lisdexamfetamine and binge-eating disorder: A systematic review and meta-analysis of the preclinical and clinical data with a focus on mechanism of drug action in treating the disorder

Binge-Eating Disorder (BED) is the most common eating disorder in the United States. Lisdexamfetamine (LDX) was approved in 2015 by the FDA for treatment of BED and is the only drug approved for treating the disorder. There has been no systematic evaluation of the published clinical and preclinical evidence for efficacy of LDX in treating BED and the mechanisms responsible for the therapeutic action of the drug. To address this gap, we conducted a systematic review and meta-analysis using PRISMA guidelines. Fourteen clinical and seven preclinical articles were included. There is consistent evidence from clinical studies that LDX is an effective treatment for BED and that the drug reduces the BED symptoms and body weight of patients with the disorder. There is also consistent evidence from preclinical studies that LDX reduces food intake but no consistent evidence for a preferential reduction of palatable food consumption by the drug in rodents. The evidence on mechanism of action is more limited and suggests LDX may reduce binge eating by a combination of effects on appetite/satiety, reward, and cognitive processes, including attention and impulsivity/inhibition, that are mediated by catecholamine and serotonin mechanisms in the brain. There is an urgent need for adequately powered, placebo-controlled, behavioural and neuroimaging studies with LDX (recruiting patients and/or individuals with subclinical BED symptoms) to further investigate the mechanism of action of the drug in treating BED. An improved understanding of the behavioural and neurochemical mechanisms of action of LDX could lead to the development of improved drug therapies to treat BED.

Identification of Food/Nonfood Visual Stimuli from Event-Related Brain Potentials

Although food consumption is one of the most basic human behaviors, the factors underlying nutritional preferences are not yet clear. The use of classification algorithms can clarify the understanding of these factors. This study was aimed at measuring electrophysiological responses to food/nonfood stimuli and applying classification techniques to discriminate the responses using a single-sweep dataset. Twenty-one right-handed male athletes with body mass index (BMI) levels between 18.5% and 25% (mean age: 21.05 ± 2.5) participated in this study voluntarily. The participants were asked to focus on the food and nonfood images that were randomly presented on the monitor without performing any motor task, and EEG data have been collected using a 16-channel amplifier with a sampling rate of 1024 Hz. The SensoMotoric Instruments (SMI) iView XTM RED eye tracking technology was used simultaneously with the EEG to measure the participants' attention to the presented stimuli. Three datasets were generated using the amplitude, time-frequency decomposition, and time-frequency connectivity metrics of P300 and LPP components to separate food and nonfood stimuli. We have implemented k-nearest neighbor (kNN), support vector machine (SVM), Linear Discriminant Analysis (LDA), Logistic Regression (LR), Bayesian classifier, decision tree (DT), and Multilayer Perceptron (MLP) classifiers on these datasets. Finally, the response to food-related stimuli in the hunger state is discriminated from nonfood with an accuracy value close to 78% for each dataset. The results obtained in this study motivate us to employ classifier algorithms using the features obtained from single-trial measurements in amplitude and time-frequency space instead of applying more complex ones like connectivity metrics.

The Neurobiology of Binge-eating Disorder Compared with Obesity: Implications for Differential Therapeutics

PURPOSE

Emerging work indicates divergence in the neurobiologies of binge-eating disorder (BED) and obesity despite their frequent co-occurrence. This review highlights specific distinguishing aspects of BED, including elevated impulsivity and compulsivity possibly involving the mesocorticolimbic dopamine system, and discusses implications for differential therapeutics for BED.

METHODS

This narrative review describes epidemiologic, clinical, genetic, and preclinical differences between BED and obesity. Subsequently, this review discusses human neuroimaging work reporting differences in executive functioning, reward processing, and emotion reactivity in BED compared with obesity. Finally, on the basis of the neurobiology of BED, this review identifies existing and new therapeutic agents that may be most promising given their specific targets based on putative mechanisms of action relevant specifically to BED.

FINDINGS

BED is characterized by elevated impulsivity and compulsivity compared with obesity, which is reflected in divergent neurobiological characteristics and effective pharmacotherapies. Therapeutic agents that influence both reward and executive function systems may be especially effective for BED.

IMPLICATIONS

Greater attention to impulsivity/compulsivity-related, reward-related, and emotion reactivity-related processes may enhance conceptualization and treatment approaches for patients with BED. Consideration of these distinguishing characteristics and processes could have implications for more targeted pharmacologic treatment research and interventions.

'Liking' and 'wanting' in eating and food reward: Brain mechanisms and clinical implications

It is becoming clearer how neurobiological mechanisms generate 'liking' and 'wanting' components of food reward. Mesocorticolimbic mechanisms that enhance 'liking' include brain hedonic hotspots, which are specialized subregions that are uniquely able to causally amplify the hedonic impact of palatable tastes. Hedonic hotspots are found in nucleus accumbens medial shell, ventral pallidum, orbitofrontal cortex, insula cortex, and brainstem. In turn, a much larger mesocorticolimbic circuitry generates 'wanting' or incentive motivation to obtain and consume food rewards. Hedonic and motivational circuitry interact together and with hypothalamic homeostatic circuitry, allowing relevant physiological hunger and satiety states to modulate 'liking' and 'wanting' for food rewards. In some conditions such as drug addiction, 'wanting' is known to dramatically detach from 'liking' for the same reward, and this may also occur in over-eating disorders. Via incentive sensitization, 'wanting' selectively becomes higher, especially when triggered by reward cues when encountered in vulnerable states of stress, etc. Emerging evidence suggests that some cases of obesity and binge eating disorders may reflect an incentive-sensitization brain signature of cue hyper-reactivity, causing excessive 'wanting' to eat. Future findings on the neurobiological bases of 'liking' and 'wanting' can continue to improve understanding of both normal food reward and causes of clinical eating disorders.

Prisoners of Addictive Cues: Biobehavioral Markers of Overweight and Obese Adults with Food Addiction

Obesity is associated with food and eating addiction (FA), but the biobehavioral markers of this condition are poorly understood. To characterize FA, we recruited 18 healthy controls and overweight/obese adults with (n = 31) and without (n = 17) FA (H-C, FAOB, NFAOB, respectively) to assess alpha brain asymmetry at rest using electroencephalogram; event-related potentials following exposure to high-calorie food (HCF), low-calorie food (LCF), and nonfood (NF) images in a Stroop paradigm; reaction time reflective of the Stroop bias; and symptoms of depression and disordered eating behavior. The FAOB group had the greatest emotional and uncontrollable eating, depressive, and binge-eating symptoms. The FAOB group displayed lower resting left alpha brain asymmetry than that of the NFAOB group. Differently from the other groups, the FAOB group presented attenuated Stroop bias following exposure to HCF relative to NF images, as well as a lower late positive potential component (LPPb; 450-495 ms) in both frontal and occipital regions. In the total cohort, a correlation was found between the Stroop bias and the LPPb amplitude. These results point to biobehavioral hypervigilance in response to addictive food triggers in overweight/obese adults with FA. This resembles other addictive disorders but is absent in overweight/obesity without FA.

Differential Expression of DeltaFosB in Reward Processing Regions Between Binge Eating Prone and Resistant Female Rats

Binge eating (BE) is characterized by the consumption of large amounts of palatable food in a discrete period and compulsivity. Even though BE is a common symptom in bulimia nervosa (BN), binge eating disorder (BED), and some cases of other specified feeding or eating disorders, little is known about its pathophysiology. We aimed to identify brain regions and neuron subtypes implicated in the development of binge-like eating in a female rat model. We separated rats into binge eating prone (BEP) and binge eating resistant (BER) phenotypes based on the amount of sucrose they consumed following foot-shock stress. We quantified deltaFosB (ΔFosB) expression, a stably expressed Fos family member, in different brain regions involved in reward, taste, or stress processing, to assess their involvement in the development of the phenotype. The number of ΔFosB-expressing neurons was: (1) higher in BEP than BER rats in reward processing areas [medial prefrontal cortex (mPFC), nucleus accumbens (Acb), and ventral tegmental area (VTA)]; (2) similar in taste processing areas [insular cortex, IC and parabrachial nucleus (PBN)]; and (3) higher in the paraventricular nucleus of BEP than BER rats, but not different in the locus coeruleus (LC), which are stress processing structures. To study subtypes of ΔFosB-expressing neurons in the reward system, we performed in situ hybridization for glutamate decarboxylase 65 and tyrosine hydroxylase (TH) mRNA after ΔFosB immunohistochemistry. In the mPFC and Acb, the proportions of γ-aminobutyric acidergic (GABAergic) and non-GABAergic ΔFosB-expressing neurons were similar in BER and BEP rats. In the VTA, while the proportion of dopaminergic ΔFosB-expressing neurons was similar in both phenotypes, the proportion of GABAergic ΔFosB-expressing neurons was higher in BER than BEP rats. Our results suggest that reward processing brain regions, particularly the VTA, are important for the development of binge-like eating.

The effect of transcranial direct current stimulation (tDCS) on food craving, reward and appetite in a healthy population

The ability to control hedonic appetite is associated with executive functioning, originating in the prefrontal cortex (PFC). These rewarding components of food can override homeostatic mechanisms, potentiating obesogenic behaviours. Indeed, those susceptible to overconsumption appear to have PFC hypo-activation. Transcranial direct current stimulation (tDCS) over the dorsolateral PFC (DLPFC) has been shown to reduce food craving and consumption, potentially via attenuating this reward response. We examined the effects of stimulation on food reward and craving using a healthy-weight cohort. This study is amongst the first to explore the effects of tDCS on explicit and implicit components of reward for different food categories. Twenty-one healthy-weight participants (24 ± 7 years, 22.8 ± 2.3 kg m^-2) completed two sessions involving double-blind, randomised and counterbalanced anodal or sham tDCS over the right DLPFC, at 2 mA for 20 min. Food craving (Food Craving Questionnaire-State), reward (Leeds Food Preference Questionnaire), and subjective appetite (100 mm visual analogue scales) were measured pre- and post-tDCS. Eating behaviour trait susceptibility was assessed using the Three Factor Eating Questionnaire-Short Form, Control of Eating Questionnaire, and Food Craving Questionnaire-Trait-reduced. Stimulation did not alter food craving, reward or appetite in healthy-weight participants who displayed low susceptibility to overconsumption, with low trait craving, good craving control, and low uncontrolled eating and emotional eating behaviour. Implicit and explicit reward were reliable measures of hedonic appetite, suggesting these are robust targets for future tDCS research. These findings suggest that applying tDCS over the DLPFC does not change food reward response in individuals not at risk for overconsumption, and future work should focus on those at risk of overconsumption who may be more responsive to the effects of tDCS on hedonic appetite.

Investigating resting brain perfusion abnormalities and disease target-engagement by intranasal oxytocin in women with bulimia nervosa and binge-eating disorder and healthy controls

Advances in the treatment of bulimia nervosa and binge-eating disorder (BN/BED) have been marred by our limited understanding of the underpinning neurobiology. Here we measured regional cerebral blood flow (rCBF) to map resting perfusion abnormalities in women with BN/BED compared with healthy controls and investigate whether intranasal oxytocin (OT), proposed as a potential treatment, can restore perfusion in disorder-related brain circuits. Twenty-four women with BN/BED and 23 healthy women participated in a randomized, double-blind, crossover, placebo-controlled study. We used arterial spin labelling MRI to measure rCBF and the effects of an acute dose of intranasal OT (40 IU) or placebo over 18-26 min post dosing, as we have previously shown robust OT-induced changes in resting rCBF in men in a similar time-window (15-36 min post dosing). We tested for effects of treatment, diagnosis and their interaction on extracted rCBF values in anatomical regions-of-interest previously implicated in BN/BED by other neuroimaging modalities, and conducted exploratory whole-brain analyses to investigate previously unidentified brain regions. We demonstrated that women with BN/BED presented increased resting rCBF in the medial prefrontal and orbitofrontal cortices, anterior cingulate gyrus, posterior insula and middle/inferior temporal gyri bilaterally. Hyperperfusion in these areas specifically correlated with eating symptoms severity in patients. Our data did not support a normalizing effect of intranasal OT on perfusion abnormalities in these patients, at least for the specific dose (40 IU) and post-dosing interval (18-26 min) examined. Our findings enhance our understanding of resting brain abnormalities in BN/BED and identify resting rCBF as a non-invasive potential biomarker for disease-related changes and treatment monitoring. They also highlight the need for a comprehensive investigation of intranasal OT pharmacodynamics in women before we can fully ascertain its therapeutic value in disorders affecting predominantly this gender, such as BN/BED.

Comparison of volumetric and shape changes of subcortical structures based on 3-dimensional image between obesity and normal-weighted subjects using 3.0 T MRI

The morphological changes of the brain, particularly in the integrity of white and gray matter and the cortical thickness of brain, have been investigated extensively in obese patients. While there has been a growing amount of evidence indicating that subcortical structures are associated with obesity, studies on the volume of subregional level including shape alterations using high-field MRI are very sparse. The aim of this study was to evaluate and compare the volumes of 14 subcortical structures (bilateral thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala, nucleus accumbens) in obese and normal-weighted subjects using 3T MRI for high resolution imaging. Fifty-four volunteers, 27 obesity (age = 23.15 ± 3.22, body mass index (BMI) = 30.12 ± 3.77) and 27 normal weighted controls (age = 26.1 ± 5.78, BMI = 21.76 ± 1.74) participated in the study. Through volumetric analysis, we found that the obese subjects had enlarged bilateral thalamus, putamen, pallidus and hippocampus, reduced bilateral caudate in obese groups in comparison to normal-weighted groups. Furthermore, we found that the medial-dorsal part of bilateral caudate significantly shrank while the lateral-dorsal part of bilateral thalamus significantly increased through vertex-based analysis (p < 0.05). Thus, based on our evidence, we suggest that subcortical structures are associated with feeding behavior and sensory function in obese patients.

A Pilot Study of Neural Correlates of Loss of Control Eating in Children With Overweight/Obesity: Probing Intermittent Access to Food as a Means of Eliciting Disinhibited Eating

Objective

Neural substrates of loss of control (LOC) eating are undercharacterized. We aimed to model intermittent access to food to elicit disinhibited eating in youth undergoing neuroimaging, given evidence that restricted food access may increase subsequent food intake via enhancing reward value of food and diminishing eating-related self-control.

Methods

Participants were 18 preadolescents (aged 9-12 years) who were overweight/obese with recent LOC eating (OW-LOC; n = 6); overweight/obese with no history of LOC eating (OW-CON; n = 5); or non-overweight with no history of LOC eating (NW-CON; n = 7). Participants underwent functional magnetic resonance imaging during a simulated food restriction paradigm in which they were alternately given restricted or unrestricted access to milkshake solutions.

Results

There were no significant main effects of restricted versus unrestricted access to milkshake flavors. Group main effects revealed increased activation for OW-LOC relative to OW-CON in areas related to attentional processes (right middle frontal gyrus), inhibitory control/attentional shifts (right and left cuneus), and emotion regulation (left cingulate gyrus); and for OW-LOC relative to NW-CON in areas related to response inhibition (right inferior frontal gyrus). Significant block type × group interaction effects were found for the right middle frontal gyrus, left cingulate gyrus, and left cuneus, but these appeared to be accounted for primarily by group.

Discussion

There were clear group differences in neural activity in brain regions related to self-regulation during a food restriction paradigm. Elevations in these regions among OW-LOC relative to OW-CON and NW-CON, respectively, may suggest that youth with LOC eating expended more cognitive effort to regulate ingestive behavior.

Abnormal structural brain network and hemisphere-specific changes in bulimia nervosa

Bulimia nervosa (BN) is characterized by episodic binge eating and purging behaviors. Disrupted neural processes of self-regulation, taste-rewarding, and body image has been associated with the pathogenesis of BN. However, the structural basis for these behavioral and functional deficits remains largely unknown. We employed diffusion tensor imaging and graph theory approaches (including the nodal properties and network-based statistics (NBS)) to characterize the whole-brain structural network of 48 BN and 44 healthy women. For nodal measures of strength, local efficiency, and betweenness centrality, BN patients displayed abnormal increases in multiple left-lateralized nodes within the mesocorticolimbic reward circuitry (including the orbitofrontal cortex, anterior cingulate, insular, medial temporal, and subcortical areas), lateral temporal-occipital cortex, and precuneus, while reduced global efficiency was observed in the right-lateralized nodes within the dorsolateral prefrontal cortex, mesocorticolimbic circuitry, somatosensory and visuospatial system. Several mesocorticolimbic nodes significantly correlated with BN symptoms. At a network level, we found increased left-lateralized connections primarily within the orbitofrontal cortex and its connections to mesocorticolimbic and lateral temporal-occipital areas, but reduced right-lateralized connections across the inferior frontal gyrus and insula, as well as their connections to the lateral temporal cortex. This study revealed BN-related changes in white-matter connections across the prefrontal control, mesocorticolimbic reward, somatosensory and visuospatial systems. The hemispheric-specific change could be an important aspect of the pathophysiology of BN. By characterizing whole-brain structural network changes of BN, our study provides novel evidence for understanding the behavioral and functional deficits of the disorder.

Update on Binge Eating Disorder

Binge eating disorder (BED) is the most common eating disorder and an important public health problem. Lifetime prevalence of BED in the United States is 2.6%. In contrast to other eating disorders, the female to male ratio in BED is more balanced. BED co-occurs with a plethora of psychiatric disorders, most commonly mood and anxiety disorders. BED is also associated with obesity and its numerous complications. Although BED is similar in men and women in presentation and treatment outcomes, there are some key neurobiological differences that should be taken in consideration when personalizing treatment.

Effect of lisdexamfetamine on emotional network brain dysfunction in binge eating disorder

We examined the effects of lisdexamfetamine (LDX) treatment on ventral prefrontal cortex (VPFC) and striatal brain activation in binge eating disorder (BED). We hypothesized that participants with BED have an abnormal brain response to palatable food cues, and that VPFC and striatal regions would respond to such cues after LDX treatment. Twenty women with moderate to severe BED consented to a 12-week, open-label trial of LDX with fMRI before and after treatment. Twenty obese women without BED served as healthy controls and received one fMRI. LDX was started at 30 mg/d with a target of 70 mg/d at week 12. At baseline, women with BED showed greater activation in ventrolateral prefrontal cortex (VLPFC), striatum, and globus pallidus to food pictures and brain activation to food pictures predicted clinical outcome at 12 weeks. After 12 weeks of LDX treatment, BED women showed significant reductions in globus pallidus activation. Reductions in ventromedial prefrontal cortex (VMPFC) and thalamus activation specifically correlated with binge eating and obsessive-compulsive symptom reductions, respectively. Results suggest that BED is characterized by an abnormally large VPFC-subcortical brain response to palatable foods that LDX treatment helps modify. Moreover, VPFC-subcortical activation at baseline is a potential biomarker of LDX response.

Neuroimaging in bulimia nervosa and binge eating disorder: a systematic review

OBJECTIVE

In recent decades there has been growing interest in the use of neuroimaging techniques to explore the structural and functional brain changes that take place in those with eating disorders. However, to date, the majority of research has focused on patients with anorexia nervosa. This systematic review addresses a gap in the literature by providing an examination of the published literature on the neurobiology of individuals who binge eat; specifically, individuals with bulimia nervosa (BN) and binge eating disorder (BED).

METHODS

A systematic review was conducted in accordance with PRISMA guidelines using PubMed, PsycInfo, Medline and Web of Science, and additional hand searches through reference lists. 1,003 papers were identified in the database search. Published studies were included if they were an original research paper written in English; studied humans only; used samples of participants with a diagnosed eating disorder characterised by recurrent binge eating; included a healthy control sample; and reported group comparisons between clinical groups and healthy control groups.

RESULTS

Thirty-two papers were included in the systematic review. Significant heterogeneity in the methods used in the included papers coupled with small sample sizes impeded the interpretation of results. Twenty-one papers utilised functional Magnetic Resonance Imaging (fMRI); seven papers utilized Magnetic Resonance Imaging (MRI) with one of these using both MRI and Positron Emission Technology (PET); three studies used Single-Photon Emission Computed Tomography (SPECT) and one study used PET only. A small number of consistent findings emerged in individuals in the acute phase of illness with BN or BED including: volume reduction and increases across a range of areas; hypoactivity in the frontostriatal circuits; and aberrant responses in the insula, amygdala, middle frontal gyrus and occipital cortex to a range of different stimuli or tasks; a link between illness severity in BN and neural changes; diminished attentional capacity and early learning; and in SPECT studies, increased rCBF in relation to disorder-related stimuli.

CONCLUSIONS

Studies included in this review are heterogenous, preventing many robust conclusions from being drawn. The precise neurobiology of BN and BED remains unclear and ongoing, large-scale investigations are required. One clear finding is that illness severity, exclusively defined as the frequency of binge eating or bulimic episodes, is related to greater neural changes. The results of this review indicate additional research is required, particularly extending findings of reduced cortical volumes and diminished activity in regions associated with self-regulation (frontostriatal circuits) and further exploring responses to disorder-related stimuli in people with BN and BED.

Food-related salience processing in healthy subjects during word recognition: Fronto-parietal network activation as revealed by independent component analysis

BACKGROUND

The study aimed to isolate and localize mutually independent cognitive processes evoked during a word recognition task involving food-related and food-neutral words using independent component analysis (ICA) for continuously recorded EEG data. Recognition memory (old/new effect) involves cognitive subcomponents-familiarity and recollection-which may be temporally and spatially dissociated in the brain. Food words may evoke additional attentional salience which may interact with the old/new effect.

METHODS

Sixteen satiated female participants undertook a word recognition task consisting of an encoding phase (learning of presented words, 40 food-related and 40 food neutral) and a test phase (recognition of previously learned words and new words). Simultaneously recorded 64-channel EEG data were decomposed into mutually independent components using the Infomax algorithm in EEGLAB. The components were localized using single dipole fitting using a four-shell BESA head model. The resulting (nonartefactual) components with <15% residual variance were clustered across subjects using the kmeans algorithm resulting in five meaningful clusters localized to fronto-parietal regions. Repeated-measures anova was employed to test main effects (old/new and food relevance) and their interaction on cluster time courses.

RESULTS

Early task-relevant old/new effects were localized to the medial frontal gyrus (MFG) and later old/new effects to the right parietal regions (precuneus). Food-related (nontask-relevant) salience effects were localized to bilateral parietal regions (left precuneus and right postcentral gyrus). Food-related salience interacted with task relevance, the old/new effect in MFG being significant only for food-neutral words highlighting central the role of MFG as the converging site of endogenous and exogenous salience inputs.

CONCLUSION

Our results indicate ICA to be a valid technique to decompose complex neurophysiological signals involving multiple cognitive processes and implicate the fronto-parietal network as an important attentional network for processing salience and task demands.

Prefrontal Cortical Opioids and Dysregulated Motivation: A Network Hypothesis

Loss of inhibitory control over appetitively motivated behavior occurs in multiple psychiatric disorders, including drug abuse, behavioral addictions, and eating disorders with binge features. In this opinion article, novel actions of μ-opioid peptides in the prefrontal cortex (PFC) that could contribute to inhibitory control deficits will be discussed. Evidence has accrued to suggest that excessive intra-PFC μ-opioid receptor (μ-OR) signaling alters the PFC response to excitatory drive, resulting in supernormal and incoherent recruitment of multiple PFC output pathways. Affected pathways include functionally opposed PFC→hypothalamus 'appetitive driver' and PFC→striatum 'appetitive limiter' projections. This network perturbation engenders disorganized, impulsive appetitive responses. Evidence supporting this hypothesis from human imaging and animal studies will be discussed, and combinatorial drug treatments targeting μ-ORs and specific PFC subcortical targets will be explored.

Explicit and Implicit Approach vs. Avoidance Tendencies towards High vs. Low Calorie Food Cues in Patients with Obesity and Active Binge Eating Disorder

Patients with binge eating disorder (BED) suffer from regular food binges with loss of control. This may be due to dysfunctional approach vs. avoidance tendencies towards food in BED. We applied an approach-avoidance task (AAT), in which n = 24 patients with obesity and active BED (OB-BED), n = 32 patients with obesity without current BED (OB), and n = 25 healthy controls (CO) either approached (“pulled”) or avoided (“pushed”) high (HC) vs. low calorie (LC) food pictures. We tested the hypothesis that OB-BED patients would show an approach bias (measured as different response times RT) towards HC food compared to the other groups. While there was no main effect for group or direction of movement, a significant main effect for calorie (p < 0.001; RT for HC significantly slower than for LC) was found. Repeated measures ANOVA (rm-ANOVA) for comparison of OB-BED vs. OB vs. CO revealed a significant three-fold interaction group × direction × calorie (p = 0.02). Against our hypothesis, the OB-BED group showed an avoidance bias for LC. In explicit ratings, OB-BED reported a significantly reduced urge to consume LC food compared to the OB group. Similar to OB-BED, CO also showed an avoidance bias for LC. The implications of our results are discussed and future directions in this field of research are presented.

Binge-eating disorder: Clinical and therapeutic advances

Binge-eating disorder (BED) is the most prevalent eating disorder with estimates of 2-5% of the general adult population. Nonetheless, its pathophysiology is poorly understood. Furthermore, there exist few therapeutic options for its effective treatment. Here we review the current state of binge-eating neurobiology and pharmacology, drawing from clinical therapeutic, neuroimaging, cognitive, human genetic and animal model studies. These studies, which are still in their infancy, indicate that while there are many gaps in our knowledge, several key neural substrates appear to underpin binge-eating and may be conserved between human and animals. This observation suggests that behavioral intermediate phenotypes or endophenotypes relevant to BED may be modeled in animals, facilitating the identification and testing of novel pharmacological targets. The development of novel, safe and effective pharmacological therapies for the treatment of BED will enhance the ability of clinicians to provide optimal care for people with BED.

An Open Trial Targeting Food Cue Reactivity and Satiety Sensitivity in Overweight and Obese Binge Eaters

Data suggests that individuals who binge eat are more responsive to food cues in the environment and less sensitive to satiety cues. The aim of this open trial was to evaluate the feasibility, acceptability, and initial effectiveness of a novel treatment grounded in Schachter's externality theory targeting food cue reactivity and satiety responsiveness with obese adults who binge eat. Treatment was provided in groups, and utilized appetite monitoring, cue-exposure treatment, in vivo exercises, self-monitoring, and coping skills. Twenty-eight overweight and obese adults who binge eat (82% female; mean age = 47.5 years [SD = 12.8]; BMI = 38.9 [SD = 10.3]; 79% White non-Hispanic) participated in a 4-month group-based treatment program. Assessments were conducted at baseline, posttreatment, and 3-month follow-up time points. Results indicated that this treatment was well accepted and had high retention at posttreatment. Initial effectiveness showed significant decreases in BMI, and improvements in loss of control and overeating episodes, food responsiveness, and power of food. The majority of results were maintained at the 3-month follow-up time point. This open trial provides preliminary evidence for the feasibility, acceptability, and initial effectiveness of this treatment on both eating disorder symptoms and weight in obese adults who binge eat. Because these data are preliminary, further treatment development and randomized controlled studies are needed.

Binge Eating Disorder

Binge eating disorder (BED) is the most common eating disorder and an important public health problem. Lifetime prevalence of BED in the United States is 2.6%. In contrast to other eating disorders, the female to male ratio in BED is more balanced. BED co-occurs with a plethora of psychiatric disorders, most commonly mood and anxiety disorders. BED is also associated with obesity and its numerous complications. Although BED is similar in men and women in presentation and treatment outcomes, there are some key neurobiological differences that should be taken in consideration when personalizing treatment.

Feeding-modulatory effects of mu-opioids in the medial prefrontal cortex: a review of recent findings and comparison to opioid actions in the nucleus accumbens

RATIONALE

Whereas reward-modulatory opioid actions have been intensively studied in subcortical sites such as the nucleus accumbens (Acb), the role of cortical opioid transmission has received comparatively little attention.

OBJECTIVES

The objective of this study is to describe recent findings on the motivational actions of opioids in the prefrontal cortex (PFC), emphasizing studies of food motivation and ingestion. PFC-based opioid effects will be compared/contrasted to those elicited from the Acb, to glean possible common functional principles. Finally, the motivational effects of opioids will be placed within a network context involving the PFC, Acb, and hypothalamus.

RESULTS

Mu-opioid receptor (μ-OR) stimulation in both the Acb and PFC induces eating and enhances food-seeking instrumental behaviors; μ-OR signaling also enhances taste reactivity within a highly circumscribed zone of medial Acb shell. In both the Acb and PFC, opioid-sensitive zones are aligned topographically with the sectors that project to feeding-modulatory zones of the hypothalamus and intact glutamate transmission in the lateral/perifornical (LH-PeF) hypothalamic areas is required for both Acb- and PFC-driven feeding. Conversely, opioid-mediated feeding responses elicited from the PFC are negatively modulated by AMPA signaling in the Acb shell.

CONCLUSIONS

Opioid signaling in the PFC engages functionally opposed PFC➔hypothalamus and PFC➔Acb circuits, which, respectively, drive and limit non-homeostatic feeding, producing a disorganized and "fragmented" pattern of impulsive food-seeking behaviors and hyperactivity. In addition, opioids act directly in the Acb to facilitate food motivation and taste hedonics. Further study of this cortico-striato-hypothalamic circuit, and incorporation of additional opioid-responsive telencephalic structures, could yield insights with translational relevance for eating disorders and obesity.

Posterior resting state EEG asymmetries are associated with hedonic valuation of food

Research on the hedonic value of food has been important in understanding the motivational and emotional correlates of normal and abnormal eating behaviour. The aim of the present study was to explore associations between hemispheric asymmetries recorded during resting state electroencephalogram (EEG) and hedonic valuation of food. Healthy adult volunteers were recruited and four minutes of resting state EEG were recorded from the scalp. Hedonic food valuation and reward sensitivity were assessed with the hedonic attitude to food and behavioural activation scale. Results showed that parieto-occipital resting state EEG asymmetries in the alpha (8-12Hz) and beta (13-30Hz) frequency range correlate with the hedonic valuation of food. Our findings suggest that self-reported sensory-related attitude towards food is associated with interhemispheric asymmetries in resting state oscillatory activity. Our findings contribute to understanding the electrophysiological correlates of hedonic valuation, and may provide an opportunity to modulate the cortical imbalance by using non-invasive brain stimulation methods to change food consumption.

Alleged Approach-Avoidance Conflict for Food Stimuli in Binge Eating Disorder

OBJECTIVE

Food stimuli are omnipresent and naturally primary reinforcing stimuli. One explanation for the intake of high amounts of food in binge eating disorder (BED) is a deviant valuation process. Valuation of food stimuli is supposed to influence approach or avoidance behaviour towards food. Focusing on self-reported and indirect (facial electromyography) valuation process, motivational aspects in the processing of food stimuli were investigated.

METHODS

We compared an overweight sample with BED (BED+) with an overweight sample without BED (BED-) and with normal weight controls (NWC) regarding their self-reported and indirect (via facial electromyography) valuation of food versus non-food stimuli.

RESULTS

Regarding the self-reported valuation, the BED+ sample showed a significantly stronger food-bias compared to the BED- sample, as food stimuli were rated as significantly more positive than the non-food stimuli in the BED+ sample. This self-reported valuation pattern could not be displayed in the indirect valuation. Food stimuli evoked negative indirect valuation in all groups. The BED+ sample showed the plainest approach-avoidance conflict marked by a diverging self-reported (positive) and indirect (negative) valuation of food stimuli.

CONCLUSIONS

BED+ showed a deviant self-reported valuation of food as compared to BED-. The valuation process of the BED+ sample seems to be characterized by a motivational ambivalence. This ambivalence should be subject of further studies and may be of potential use for therapeutic interventions.

The neurobiological basis of binge-eating disorder

Relatively little is known about the neuropathophysiology of binge-eating disorder (BED). Here, the evidence from neuroimaging, neurocognitive, genetics, and animal studies are reviewed to synthesize our current understanding of the pathophysiology of BED. Binge-eating disorder may be conceptualized as an impulsive/compulsive disorder, with altered reward sensitivity and food-related attentional biases. Neuroimaging studies suggest there are corticostriatal circuitry alterations in BED similar to those observed in substance abuse, including altered function of prefrontal, insular, and orbitofrontal cortices and the striatum. Human genetics and animal studies suggest that there are changes in neurotransmitter networks, including dopaminergic and opioidergic systems, associated with binge-eating behaviors. Overall, the current evidence suggests that BED may be related to maladaptation of the corticostriatal circuitry regulating motivation and impulse control similar to that found in other impulsive/compulsive disorders. Further studies are needed to understand the genetics of BED and how neurotransmitter activity and neurocircuitry function are altered in BED and how pharmacotherapies may influence these systems to reduce BED symptoms.

Neurobiological features of binge eating disorder

Biobehavioral features associated with binge-eating disorder (BED) have been investigated; however, few systematic reviews to date have described neuroimaging findings from studies of BED. Emerging functional and structural studies support BED as having unique and overlapping neural features as compared with other disorders. Neuroimaging studies provide evidence linking heightened responses to palatable food cues with prefrontal areas, particularly the orbitofrontal cortex (OFC), with specific relationships to hunger and reward-sensitivity measures. While few studies to date have investigated non-food-cue responses; these suggest a generalized hypofunctioning in frontostriatal areas during reward and inhibitory control processes. Early studies applying neuroimaging to treatment efforts suggest that targeting neural function underlying motivational processes may prove important in the treatment of BED.

Are Eating Disorders Related to Attention Deficit/Hyperactivity Disorder?

Attention deficit/hyperactivity disorder (ADHD) is a disorder characterized by impulsivity, hyperactivity, and inattention. Binge-eating behavior is often impulsive and is the hallmark of the two eating disorders, binge-eating disorder (BED) and bulimia nervosa (BN), both of which are associated with significant health impairment. Bingeing behavior is also seen in the binge purge subtype of anorexia nervosa. Individuals with AN of the binge purge subtypes, BN and BED, have been found to exhibit impulsive behaviors that are often not limited to binge eating alone. There is preliminary evidence linking ADHD to BN and to BED in both adults and children. The neurobiological mechanisms behind these associations are only beginning to emerge; however, they suggest that impulse control deficits may play a role in these eating disorders. Additionally, although they may not meet full criteria for one of these eating disorders, some adults and children with ADHD present with dysregulated, impulsive eating disorder behaviors and there is a growing association between ADHD, obesity, and binge-eating behavior in both children and adults. The relationship between ADHD and binge eating is novel, supported by growing evidence and worthy of further research. We will review the underlying neurobiological underpinnings, neuroimaging data, and possible psychopharmacological treatment options, which target both ADHD and binge-eating behaviors as well as future research and treatment directions.

Cognitive and emotional functioning in binge-eating disorder: A systematic review

OBJECTIVE

Binge-eating disorder (BED) is characterized by recurrent episodes of binge eating and is associated with eating disorder and general psychopathology and overweight/obesity. Deficits in cognitive and emotional functioning for eating disorders or obesity have been reported. However, a systematic review on cognitive and emotional functioning for individuals with BED is lacking.

METHOD

A systematic literature search was conducted across three databases (Medline, PubMed, and PsycINFO). Overall, n = 57 studies were included in the present review.

RESULTS

Regarding cognitive functioning (CoF), individuals with BED consistently demonstrated higher information processing biases compared to obese and normal-weight controls in the context of disorder-related stimuli (i.e., food and body cues), whereas CoF in the context of neutral stimuli appeared to be less affected. Thus, results suggest disorder-related rather than general difficulties in CoF in BED. With respect to emotional functioning (EmF), individuals with BED reported difficulties similar to individuals with other eating disorders, with a tendency to show less severe difficulties in some domains. In addition, individuals with BED reported greater emotional deficits when compared to obese and normal-weight controls. Findings suggest general difficulties in EmF in BED. Thus far, however, investigations of EmF in disorder-relevant situations are lacking.

DISCUSSION

Overall, the cross-sectional findings indicate BED to be associated with difficulties in CoF and EmF. Future research should determine the nature of these difficulties, in regards to general and disorder-related stimuli, and consider interactions of both domains to foster the development and improvement of appropriate interventions in BED.

Endogenous Opioid Signaling in the Medial Prefrontal Cortex is Required for the Expression of Hunger-Induced Impulsive Action

Opioid transmission and dysregulated prefrontal cortex (PFC) activity have both been implicated in the inhibitory-control deficits associated with addiction and binge-type eating disorders. What remains unknown, however, is whether endogenous opioid transmission within the PFC modulates inhibitory control. Here, we compared intra-PFC opioid manipulations with a monoamine manipulation (d-amphetamine), in two sucrose-reinforced tasks: progressive ratio (PR), which assays the motivational value of an incentive, and differential reinforcement of low response rates (DRLs), a test of inhibitory control. Intra-PFC methylnaloxonium (M-NX, a limited diffusion opioid antagonist) was given to rats in a 'low-drive' condition (2-h food deprivation), and also after a motivational shift to a 'high-drive' condition (18-h food deprivation). Intra-PFC DAMGO (D-[Ala2,N-MePhe4, Gly-ol]-enkephalin; a μ-opioid agonist) and d-amphetamine were also tested in both tasks, under the low-drive condition. Intra-PFC M-NX nearly eliminated impulsive action in DRL engendered by hunger, at a dose (1 μg) that significantly affected neither hunger-induced PR enhancement nor hyperactivity. At a higher dose (3 μg), M-NX eliminated impulsive action and returned PR breakpoint to low-drive levels. Conversely, intra-PFC DAMGO engendered 'high-drive-like' effects: enhancement of PR and impairment of DRL performance. Intra-PFC d-amphetamine failed to produce effects in either task. These results establish that endogenous PFC opioid transmission is both necessary and sufficient for the expression of impulsive action in a high-arousal, high-drive appetitive state, and that PFC-based opioid systems enact functionally unique effects on food impulsivity and motivation relative to PFC-based monoamine systems. Opioid antagonists may represent effective treatments for a range of psychiatric disorders with impulsivity features.

Greater anterior cingulate activation and connectivity in response to visual and auditory high-calorie food cues in binge eating: Preliminary findings

Obese individuals show altered neural responses to high-calorie food cues. Individuals with binge eating [BE], who exhibit heightened impulsivity and emotionality, may show a related but distinct pattern of irregular neural responses. However, few neuroimaging studies have compared BE and non-BE groups. To examine neural responses to food cues in BE, 10 women with BE and 10 women without BE (non-BE) who were matched for obesity (5 obese and 5 lean in each group) underwent fMRI scanning during presentation of visual (picture) and auditory (spoken word) cues representing high energy density (ED) foods, low-ED foods, and non-foods. We then compared regional brain activation in BE vs. non-BE groups for high-ED vs. low-ED foods. To explore differences in functional connectivity, we also compared psychophysiologic interactions [PPI] with dorsal anterior cingulate cortex [dACC] for BE vs. non-BE groups. Region of interest (ROI) analyses revealed that the BE group showed more activation than the non-BE group in the dACC, with no activation differences in the striatum or orbitofrontal cortex [OFC]. Exploratory PPI analyses revealed a trend towards greater functional connectivity with dACC in the insula, cerebellum, and supramarginal gyrus in the BE vs. non-BE group. Our results suggest that women with BE show hyper-responsivity in the dACC as well as increased coupling with other brain regions when presented with high-ED cues. These differences are independent of body weight, and appear to be associated with the BE phenotype.

Altered frontal inter-hemispheric resting state functional connectivity is associated with bulimic symptoms among restrained eaters

Theory and research have indicated that restrained eating (RE) increases risk for binge-eating and eating disorder symptoms. According to the goal conflict model, such risk may result from disrupted hedonic-feeding control and its interaction with reward-driven eating. However, RE-related alterations in functional interactions among associated underlying brain regions, especially between the cerebral hemispheres, have rarely been examined directly. Therefore, we investigated inter-hemispheric resting-state functional connectivity (RSFC) among female restrained eaters (REs) (n=23) and unrestrained eaters (UREs) (n=24) following food deprivation as well as its relation to overall bulimia nervosa (BN) symptoms using voxel-mirrored homotopic connectivity (VMHC). Seed-based RSFC associated with areas exhibiting significant VMHC differences was also assessed. Compared to UREs, REs showed reduced VMHC in the dorsal-lateral prefrontal cortex (DLPFC), an area involved in inhibiting hedonic overeating. REs also displayed decreased RSFC between the right DLPFC and regions associated with reward estimation--the ventromedial prefrontal cortex (VMPFC) and posterior cingulate cortex (PCC). Finally, bulimic tendencies had a negative correlation with VMHC in the DLPFC and a positive correlation with functional connectivity (DLPFC and VMPFC) among REs but not UREs. Findings suggested that reduced inter-hemispheric functional connectivity in appetite inhibition regions and altered functional connectivity in reward related regions may help to explain why some REs fail to control hedonically-motivated feeding and experience higher associated levels of BN symptomatology.

Volumetric alterations in the nucleus accumbens and caudate nucleus in bulimia nervosa: a structural magnetic resonance imaging study

OBJECTIVE

Bulimia nervosa (BN) is an eating disorder characterized by recurrent episodes of binge eating and inappropriate compensatory behaviors (such as purging, fasting, or excessive exercise) to prevent weight gain. BN has been associated with deficits in inhibitory control processes. The basal ganglia specifically, the nucleus accumbens (NAc) and the caudate nucleus (CN) are part of the frontostriatal circuits involved in inhibitory control. The main goal of this study was to investigate the presence of morphological alterations in the NAc and the CN in a sample of patients diagnosed with BN.

METHOD

Forty-one female participants, 21 diagnosed with BN and 20 healthy matched controls (HC), underwent a structural magnetic resonance imaging (MRI) acquisition and clinical assessment. The NAc and the CN were manually segmented using the software Slicer 3D.

RESULTS

The results reveal a significant volumetric decrease in the CN and a preserved NAc volume in BN compared to the control group.

DISCUSSION

These findings suggest a contributory role of the caudate nucleus part of the dorsal striatum in the psychopathology of BN.

Differential reward response to palatable food cues in past and current dieters: a fMRI study

OBJECTIVE

Prior neuroimaging research has shown that restrained and unrestrained eaters demonstrate differential brain activation in response to food cues that parallels their food intake in lab studies. These findings were extended by comparing brain activation in response to food cues in normal weight nondieters, historical dieters, and current dieters under the conditions that mimicked past lab studies.

METHODS

Participants (N = 30) were shown pictures of highly and moderately palatable food and neutral cues while being scanned in an fMRI BOLD paradigm following an 8-h fast and again after a liquid meal.

RESULTS

In the Fed state, historical dieters showed elevated reward circuitry activation in response to highly palatable food, as compared to nondieters and current dieters. In contrast, current dieters did not show the same pattern of activation as historical dieters, despite their shared history of frequent weight-loss dieting.

CONCLUSIONS

The parallels between eating behavior and regional brain activation across groups suggest that (1) a neurophysiological response which could represent a vulnerability to overeat exists in some normal weight young women that may increase susceptibility to weight gain in the long term, and (2) current dieting temporarily reverses this vulnerability.

Brain imaging and human nutrition: which measures to use in intervention studies?

The present review describes brain imaging technologies that can be used to assess the effects of nutritional interventions in human subjects. Specifically, we summarise the biological relevance of their outcome measures, practical use and feasibility, and recommended use in short- and long-term nutritional studies. The brain imaging technologies described consist of MRI, including diffusion tensor imaging, magnetic resonance spectroscopy and functional MRI, as well as electroencephalography/magnetoencephalography, near-IR spectroscopy, positron emission tomography and single-photon emission computerised tomography. In nutritional interventions and across the lifespan, brain imaging can detect macro- and microstructural, functional, electrophysiological and metabolic changes linked to broader functional outcomes, such as cognition. Imaging markers can be considered as specific for one or several brain processes and as surrogate instrumental endpoints that may provide sensitive measures of short- and long-term effects. For the majority of imaging measures, little information is available regarding their correlation with functional endpoints in healthy subjects; therefore, imaging markers generally cannot replace clinical endpoints that reflect the overall capacity of the brain to behaviourally respond to specific situations and stimuli. The principal added value of brain imaging measures for human nutritional intervention studies is their ability to provide unique in vivo information on the working mechanism of an intervention in hypothesis-driven research. Selection of brain imaging techniques and target markers within a given technique should mainly depend on the hypothesis regarding the mechanism of action of the intervention, level (structural, metabolic or functional) and anticipated timescale of the intervention's effects, target population, availability and costs of the techniques.

Review

Neuroanatomical and functional studies in the eating disorders (ED) are reviewed. Typically, anorexia nervosa (AN) is associated with cerebral spinal fluid spaces enlargement which generally recover as a function of re-feeding. However, specific cortical areas fail to correct in weight restored anorectic patients suggesting trait-related abnormalities. Functional changes in AN associated with starvation reverse with weight recovery, however, reduced 5-HT2A receptor binding may be fundamental to the pathophysiology of AN since this remains after long term weight restoration. Structural studies of bulimia nervosa (BN) provide evidence of brain atrophy, in the absence of significant weight loss but potentially related to chronic dietary restriction. Functional investigations reveal reduced thalamic and hypothalamic serotonin transporter availability in BN which increases with longer illness duration. Thus, BN is associated with substantial structural and functional alterations despite normal weight. Recent advances in neuroimaging techniques and their interpretation are increasing our understanding of normal processes in the control of food intake including neuroanatomical correlates of hunger and satiety. Taken together with the structural and functional changes observed in the ED, neuroimaging provides a powerful platform to identify the underlying trait-related pathophysiological mechanisms in the aetiology and maintenance of AN and BN.