Reduced Plasma Orexin-A Concentrations are Associated with Cognitive Deficits in Anorexia Nervosa

Drinking severity mediates the relationship between hypothalamic connectivity and rule-breaking/intrusive behavior differently in young women and men: an exploratory study

Background

The hypothalamus is a key hub of the neural circuits of motivated behavior. Alcohol misuse may lead to hypothalamic dysfunction. Here, we investigated how resting-state hypothalamic functional connectivities are altered in association with the severity of drinking and clinical comorbidities and how men and women differ in this association.

Methods

We employed the data of the Human Connectome Project. A total of 870 subjects were included in data analyses. The severity of alcohol use was quantified for individual subjects with the first principal component (PC1) identified from principal component analyses of all drinking measures. Rule-breaking and intrusive scores were evaluated with the Achenbach Adult Self-Report Scale. We performed a whole-brain regression of hypothalamic connectivities on drinking PC1 in all subjects and men/women separately and evaluated the results at a corrected threshold.

Results

Higher drinking PC1 was associated with greater hypothalamic connectivity with the paracentral lobule (PCL). Hypothalamic PCL connectivity was positively correlated with rule-breaking score in men (r=0.152, P=0.002) but not in women. In women but not men, hypothalamic connectivity with the left temporo-parietal junction (LTPJ) was negatively correlated with drinking PC1 (r=-0.246, P<0.001) and with intrusiveness score (r=-0.127, P=0.006). Mediation analyses showed that drinking PC1 mediated the relationship between hypothalamic PCL connectivity and rule-breaking score in men and between hypothalamic LTPJ connectivity and intrusiveness score bidirectionally in women.

Conclusions

We characterized sex-specific hypothalamic connectivities in link with the severity of alcohol misuse and its comorbidities. These findings extend the literature by elucidating the potential impact of problem drinking on the motivation circuits.

Endocrinology-informed neuroimaging in eating disorders: GLP1, orexins, and psilocybin

The neurobiology of eating disorders [EDs; anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED)] remains poorly understood. Here, I describe how neuroimaging, accompanied by peripheral endocrine measures, can provide insights into the neurobiological drivers of eating disorders. Orexins/hypocretins, glucagon-like peptide-1 receptor (GLP1R) agonists, and psilocybin are highlighted as avenues for investigation.

Higher orexin-A levels are associated with treatment response to clozapine in patients with schizophrenia: A cross-sectional study

BACKGROUND

Clozapine is the primary antipsychotic (APD) for treatment-resistant schizophrenia (TRS). However, only 40% of patients with TRS respond to clozapine, constituting a subgroup of clozapine-resistant patients. Recently, the neuropeptide orexin-A was shown to be involved in the pathophysiology of schizophrenia. This study evaluated the association of orexin-A levels with the clozapine response in patients with TRS.

METHODS

We recruited 199 patients with schizophrenia, including 37 APD-free and 162 clozapine-treated patients. Clozapine-treated patients were divided into clozapine-responsive (n = 100) and clozapine-resistant (n = 62) groups based on whether they had achieved psychotic remission defined by the 18-item Brief Psychiatric Rating Scale (BPRS-18). We compared blood orexin-A levels among the three groups and performed regression analysis to determine the association of orexin-A level with treatment response in clozapine-treated patients. We also explored the correlation between orexin-A levels and cognitive function, assessed using the CogState Schizophrenia Battery.

RESULTS

Clozapine-responsive patients had higher orexin-A levels than clozapine-resistant and APD-free patients. Orexin-A level was the only factor significantly associated with treatment response after adjustment. Orexin-A levels were negatively correlated with BPRS-18 full scale and positive, negative, and general symptoms subscale scores. We also observed a positive correlation between orexin-A levels and verbal memory, visual learning and memory, and working memory function.

CONCLUSIONS

This cross-sectional study showed that higher levels of orexin-A are associated with treatment response to clozapine in patients with TRS. Future prospective studies examining changes in orexin-A level following clozapine treatment and the potential benefit of augmenting orexin-A signaling are warranted.

Investigating differences in cognitive flexibility, clinical perfectionism, and eating disorder-specific rumination across anorexia nervosa illness states

INTRODUCTION

Cognitive inflexibility, clinical perfectionism, and eating disorder (ED)-specific rumination are common characteristics reported in anorexia nervosa (AN) and may contribute to the maintenance of the illness. It is suggested that clinical perfectionism and rumination may mediate the relationship between cognitive flexibility and AN pathology; however, research to date has not investigated all these factors together. The aim of the current study was to explore the relationships between these factors and how they may relate to ED symptoms in AN.

METHODS

Participants included 15 women with a current diagnosis of AN, 12 women who had a past diagnosis of AN and were currently weight-restored, and 15 healthy controls (HCs).

RESULTS

The results revealed that participants with both acute and weight-restored AN self-reported poorer cognitive flexibility than HCs, but the groups did not differ in performance on objective assessments of cognitive flexibility. Participants with AN also reported significantly greater clinical perfectionism and ED-specific rumination than HC. A parallel mediation analysis found that ED-specific rumination mediated the relationship between subjective cognitive flexibility and ED symptoms. Further, subjective cognitive flexibility directly influenced ED symptoms. However, the mediation model was not significant for objective cognitive flexibility.

CONCLUSION

The findings of this study have implications for potential treatment barriers and factors which might contribute to the risk of relapse.

Engagement of the brain orexin system in activity-based anorexia behaviour in mice

While excessive physical activity is common amongst anorexia nervosa (AN) patients, contributing to their low body weight, little is known about the underlying biology and effective treatments targeting the hyperactivity are lacking. Given the role of orexin in arousal, physical activity and energy expenditure, we sought to investigate i) the extent to which orexin neurons are activated during severe anorectic state in the activity-based anorexia (ABA) mouse model, and ii) if the dual orexin receptor antagonist suvorexant can reduce physical activity during ABA. The Fos-TRAP2 technique enable us to visually capture active neurons (Fos expressing) during severe anorectic state in the ABA mouse model, and by immunohistochemistry, determine the extent to which these active neurons are orexin positive. In addition, suvorexant was administered peripherally to ABA mice and running activity was monitored. We found that a large population of orexin neurons in the hypothalamus are activated by ABA and that peripheral administration of suvorexant decreases food anticipatory activity in these mice. We conclude that orexin may be a suitable target to treat hyperactivity in AN and recommend further studies to examine the efficacy of suvorexant in aiding AN patients to control their drive for hyperactivity.

Temporal dynamics of cognitive flexibility in adolescents with anorexia nervosa: A high-density EEG study

Impairment in cognitive flexibility is a core symptom of anorexia nervosa (AN) and is associated with treatment resistance. Nevertheless, studies on the neural basis of cognitive flexibility in adolescent AN are rare. This study aimed to investigate brain networks underlying cognitive flexibility in adolescents with AN. To address this aim, participants performed a Dimensional Change Card Sorting task during high-density electroencephalography (EEG) recording. Anxiety was measured with the State-Trait Anxiety Inventory. Data were collected on 22 girls with AN and 23 controls. Evoked responses were investigated using global-spatial analysis. Adolescents with AN showed greater overall accuracy, fewer switch trial errors and reduced inverse efficiency switch cost relative to controls, although these effects disappeared after adjusting for trait and state anxiety. EEG results indicated augmented early visual orienting processing (P100) and subsequent impaired attentional mechanisms to task switching (P300b) in subjects with AN. During task switching, diminished activations in subjects with AN were identified in the posterior cingulate, calcarine sulcus and cerebellum, and task repetitions induced diminished activations in a network involving the medial prefrontal cortex, and several posterior regions, compared with controls. No significant associations were found between measures of cognitive flexibility and anxiety in the AN group. Findings of this study suggest atypical neural mechanisms underlying cognitive flexibility in adolescents with AN. More importantly, our findings suggest that different behavioural profiles in AN could relate to differences in anxiety levels. Future research should investigate the efficacy of cognitive training to rebalance brain networks of cognitive flexibility in AN.

Understanding self-report and neurocognitive assessments of cognitive flexibility in people with and without lifetime anorexia nervosa

Objective: Anorexia nervosa (AN) is a serious eating disorder associated with several cognitive difficulties including poor cognitive flexibility (i.e. difficulties in effectively adapting to changes in the environment and/or changing task demands). AN research has primarily assessed cognitive flexibility using neurocognitive tests, and little is known about the differences or similarities between self-report and neurocognitive assessments of cognitive flexibility. This study investigated the relationship between self-report and neurocognitive assessments of cognitive flexibility in people with no history of an eating disorder (n = 207) and people with a self-reported lifetime diagnosis of AN (n = 19).Methods: Participants completed self-report and neurocognitive assessments of cognitive flexibility through an online study.Results: No significant correlations were found between self-report and neurocognitive assessments of cognitive flexibility for either group of the sample, suggesting that these assessments may evaluate different aspects of cognitive flexibility. Further, negative mood and self-reported eating disorder symptoms were found to significantly relate to self-reported cognitive flexibility, but were not associated with performance on neurocognitive tests of cognitive flexibility.Conclusions: To provide a comprehensive understanding of perceived and objective cognitive flexibility in AN, future research and clinical assessments should include both self-report and neurocognitive assessments.

Cognitive decline in heart failure: Biomolecular mechanisms and benefits of exercise

By definition, heart failure (HF) is a human pathological condition affecting the structure and function of all organs in the body, and the brain is not an exception to that. Failure of the heart to pump enough blood centrally and peripherally is at the foundation of HF patients' inability to attend even the most ordinary daily activities and progressive deterioration of their cognitive capacity. What is more, between heart and brain exists a bidirectional relationship that goes well beyond hemodynamics and concerns bioelectric and endocrine signaling. This increasingly consolidated evidence makes the scenario even more complex. Studies have mainly chased how HF impairs cognition without focusing much on preventive measures, notably cardio-cerebral health proxies. Here, we aim to provide a brief account of known and hypothetical factors that may explain how exercise can help obviate cognitive dysfunction associated with HF in its different forms. As we shall see, there is a stringent need for a deeper grasp of such mechanisms. Indeed, gaining this new knowledge will automatically shed new light on the inner workings of HF itself, thus resulting in more effective prevention and treatment of this escalating syndrome.

Associations between daytime and nighttime plasma orexin A levels and cognitive function in patients with obstructive sleep apnea

The relationship between plasma orexin A (OXA) levels and cognitive function in patients with obstructive sleep apnea (OSA) remains unclear. This study aimed to evaluate associations between daytime and nighttime plasma OXA levels and cognitive function in patients with OSA. Subjects with suspected OSA underwent overnight polysomnography (PSG), Montreal Cognitive Assessment (MoCA), and Epworth Sleepiness Scale (ESS) assessment. Subjects were considered controls or having OSA according to the apnea-hypopnea index (AHI). Daytime and nighttime plasma OXA levels were determined by ELISA. Receiver-operating characteristics curves were used to evaluate the diagnostic value of plasma OXA levels for assessing cognitive impairment in OSA patients. One hundred and six subjects met the inclusion criteria. MoCA scores and plasma OXA concentrations were significantly lower in OSA patients than controls (p < 0.01). Patients with moderate and severe OSA had significantly lower MoCA scores than controls and mild OSA patients (p < 0.01). Daytime and nighttime OXA levels were significantly lower in OSA patients with cognitive impairment than those without cognitive impairment (p < 0.01). Both daytime and nighttime plasma OXA levels in patients with OSA were positively correlated with MoCA scores and nadir SaO2, negatively correlated with AHI, oxygen desaturation index, and percentage of time spent with an SaO2 below 90% (all p < 0.05), and not correlated with ESS scores. The optimal threshold of daytime plasma OXA to diagnose OSA with cognitive impairment was 49.34 pg/ml, with a sensitivity of 80.0% and a specificity of 74.3%. We concluded that plasma OXA concentrations might be related to cognitive function and daytime plasma OXA levels have diagnostic value for assessing cognitive impairment in OSA patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00387-4.

Maternal urban particulate matter exposure and signaling pathways in fetal brains and neurobehavioral development in offspring

It is well understood that exposure to particulate matter (PM) can have adverse effects on the nervous system. When pregnant women are exposed to PM, their fetuses are also affected through the placenta. However, the mechanisms by which fetal brain development is regulated between mother and fetus remain unclear. C57BL/6J pregnant mice were exposed to PM at embryonic day (E) 2.5, 5.5, 8.5, 11.5, 14.5, and 17.5 via nasal drip at three doses (3, 6, 12 mg/kg of body weight) or PBS control. Neurobehavioral changes in the offspring were examined at 5-6-week-old by open field test (OFT) and elevated plus maze (EPM). The maternal and fetal brain and placenta were collected at E18.5, and molecular signal changes were explored using transcriptome analysis. We found that both male and female low-dose pups and male middle-dose pups traveled a significantly longer distance than controls in EPM tests. Both male and female low-dose pups showed a higher frequency of entering the center area and female low-dose pups exhibited a higher percentage of distance moved in the center area than controls in OFT tests. Gene expression in the maternal brain, fetal brain, and placenta at E18.5 was altered. Differentially expressed genes were enriched in the neuroactive ligand-receptor interaction pathway in all three tissue types. Pathway analysis revealed that the PI3K-Akt and PKC signaling was dysregulated in the fetal brain in the high-dose group compared with the control group. The pathways play a role in neuronal survival and apoptosis. Furthermore, there is a dose-dependent increase in Caspase-6, neuronal apoptosis and neurodegeneration biomarker, levels in E18.5 fetal brain (P = 0.06). In conclusion, our study demonstrated that prenatal PM exposure enhanced exploration and locomotor activity in adolescent offspring and altered molecular events in maternal brain, fetal brain, and placenta. The connections of these changes warrant further investigations.

Hypocretins (orexins): The ultimate translational neuropeptides

The hypocretins (Hcrts), also known as orexins, are two neuropeptides produced exclusively in the lateral hypothalamus. They act on two specific receptors that are widely distributed across the brain and involved in a myriad of neurophysiological functions that include sleep, arousal, feeding, reward, fear, anxiety and cognition. Hcrt cell loss in humans leads to narcolepsy with cataplexy (narcolepsy type 1), a disorder characterized by intrusions of sleep into wakefulness, demonstrating that the Hcrt system is nonredundant and essential for sleep/wake stability. The causal link between Hcrts and arousal/wakefulness stabilisation has led to the development of a new class of drugs, Hcrt receptor antagonists to treat insomnia, based on the assumption that blocking orexin-induced arousal will facilitate sleep. This has been clinically validated: currently, two Hcrt receptor antagonists are approved to treat insomnia (suvorexant and lemborexant), with a New Drug Application recently submitted to the US Food and Drug Administration for a third drug (daridorexant). Other therapeutic applications under investigation include reduction of cravings in substance-use disorders and prevention of neurodegenerative disorders such as Alzheimer's disease, given the apparent bidirectional relationship between poor sleep and worsening of the disease. Circuit neuroscience findings suggest that the Hcrt system is a hub that integrates diverse inputs modulating arousal (e.g., circadian rhythms, metabolic status, positive and negative emotions) and conveys this information to multiple output regions. This neuronal architecture explains the wealth of physiological functions associated with Hcrts and highlights the potential of the Hcrt system as a therapeutic target for a number of disorders. We discuss present and future possible applications of drugs targeting the Hcrt system for the treatment of circuit-related neuropsychiatric and neurodegenerative conditions.

Orexin-a elevation in antipsychotic-treated compared to drug-free patients with schizophrenia: A medication effect independent of metabolic syndrome

BACKGROUND/PURPOSE

Orexin-A levels are reportedly increased in antipsychotic (APD)-treated patients with schizophrenia compared to healthy controls and have been associated with metabolic abnormalities. It is not clear whether the orexin-A elevation is related specifically to the drug (APDs) effect, which should be clarified by including a drug-free group for comparison, or related to drug-induced metabolic abnormalities.

METHODS

Blood orexin-A levels and metabolic profiles were compared between 37 drug-free, 45 aripiprazole-treated, and 156 clozapine-treated patients with schizophrenia. The association between orexin-A and metabolic outcomes were examined. We explored the effects of APDs treatment and metabolic status on orexin-A levels by linear regression.

RESULTS

Patients under APDs treatment had increased orexin-A levels compared to drug-free patients, with aripiprazole-treated group having higher orexin-A levels than clozapine-treated group. Higher orexin-A levels reduced the risks of metabolic syndrome (MS) and type 2 diabetes mellitus, indicating a relationship between orexin-A levels and metabolic problems. After adjusting the effect from metabolic problems, we found APD treatment is still associated with orexin-A regulation, with aripiprazole more significantly than clozapine.

CONCLUSION

With the inclusion of drug-free patients rather than healthy controls for comparison, we demonstrated that orexin-A is upregulated following APD treatment even after we controlled the potential effect from MS, suggesting an independent effect of APDs on orexin-A levels. Furthermore, the effect differed between APDs with dissimilar obesogenicity, i.e. less obesogenicity likely associated with higher orexin-A levels. Future prospective studies exploring the causal relationship between APDs treatment and orexin-A elevation as well as the underlying mechanisms are warranted.

Subjective sleep disorders and daytime sleepiness in patients with restrictive type anorexia nervosa and effects on quality of life: a case-control study

To evaluate sleep disorders and daytime drowsiness in a cohort of patients affected by anorexia nervosa and their impact on health-related quality of life. We evaluated patients affected by restricting-type of anorexia nervosa (AN-R) and healthy controls by the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale, Beck Depression Index. We also used the Short-Form Health Survey (SF-36) questionnaire to assess the quality of life in both AN-R and controls. Twenty-eight out of 34 AN-R patients (82.3%) in contrast with ten out of 34 healthy subjects (29.4%) had a pathological PSQI score compared to HC (p < 0.0001). The overall PSQI score (p < 0.001), sleep quality (p < 0.001), sleep duration (p = 0.02), sleep efficiency (p = 0.002), sleep disturbances (p = 0.03) and daytime dysfunction (p = 0.004) were significantly higher in AN-R than in controls. SF36 showed significantly reduced scores of standardized physical components (p = 0.01) and standardized mental components (p < 0.001), physical function (p < 0.001), physical role (p < 0.001) and general health (p < 0.001), vitality (p < 0.001), social functioning (p  < 0.001) emotional role (p = 0.001) and mental health (p < 0.001) in AN-R. We found a significant correlation between the PSQI score and both the physical role (r = - 0.35, p = 0.03) and level of education (r = 0.38, p = 0.02). Our data showed reduced overall sleep quality without excessive daytime sleepiness in AN-R. Sleep quality correlated significantly with quality of life (physical role) and level of education.

Can Cognitive Flexibility and Clinical Perfectionism Be Used to Identify People with Anorexia Nervosa?

Poor cognitive flexibility and perfectionism are common features in anorexia nervosa (AN). The current study aimed to investigate cognitive flexibility and clinical perfectionism as potential predictors of AN. Twenty women with a current diagnosis of AN (M age = 28.25, SD = 7.62) and 170 community participants with no lifetime history of an eating disorder (M age = 29.23, SD = 9.88) took part in an online cross-sectional study that included self-report questionnaires of cognitive flexibility and clinical perfectionism. It was found that compared to the community sample, women with AN self-reported significantly poorer cognitive flexibility and significantly greater clinical perfectionism. In a regression model, clinical perfectionism (but not self-reported cognitive flexibility) significantly predicted group membership. The specificity and sensitivity of the model were high. These preliminary findings indicate that clinical perfectionism may represent a key feature of AN and may accurately discriminate between participants with and without AN, though more research is required.

A review of effort-based decision-making in eating and weight disorders

Effort-based decision-making provides a framework to understand the mental computations estimating the amount of work ("effort") required to obtain a reward. The aim of the current review is to systematically synthesize the available literature on effort-based decision-making across the spectrum of eating and weight disorders. More specifically, the current review summarises the literature examining whether 1) individuals with eating disorders and overweight/obesity are willing to expend more effort for rewards compared to healthy controls, 2) if particular components of effort-based decision-making (i.e. risk, discounting) relate to specific binge eating conditions, and 3) how individual differences in effort and reward -processing measures relate to eating pathology and treatment measures. A total of 96 studies were included in our review, following PRISMA guidelines. The review suggests that individuals with binge eating behaviours 1) are more likely to expend greater effort for food rewards, but not monetary rewards, 2) demonstrate greater decision-making impairments under risk and uncertainty, 3) prefer sooner rather than delayed rewards for both food and money, and 4) demonstrate increased implicit 'wanting' for high fat sweet foods. Finally, individual differences in effort and reward -processing measures relating to eating pathology and treatment measures are also discussed.

Central coherence and set-shifting between nonunderweight eating disorders and anorexia nervosa: A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis compared previously documented inefficiencies in central coherence and set-shifting between people with nonunderweight eating disorders (bulimia nervosa and binge-eating disorder) and people with anorexia nervosa.

METHOD

We performed random-effects meta-analyses on 16 studies (1,112 participants) for central coherence and 38 studies (3,505 participants) for set-shifting. Random effects meta-regressions were used to test whether the effect sizes for people with nonunderweight eating disorders were significantly different from the effect sizes for people with anorexia nervosa.

RESULTS

People with anorexia nervosa (Hedge's g = -0.53, 95% CIs: -0.80, -0.27, p < .001) and bulimia nervosa (Hedge's g = -0.70, 95% CIs: -1.14, -0.25, p = .002), but not binge-eating disorder, had significantly poorer central coherence than healthy controls. Similarly, people with anorexia nervosa (Hedge's g = -0.38, 95% CIs: -0.50, -0.26, p < .001) and bulimia nervosa (Hedge's g = -0.55, 95% CIs: -0.81, -0.29, p < .001), but not binge-eating disorder, had significantly poorer set-shifting than healthy controls. The effect sizes for people with nonunderweight eating disorders did not significantly differ from those for people with anorexia nervosa.

DISCUSSION

Our meta-analysis was underpowered to make definitive judgments about people with binge-eating disorder. However, we found that people with bulimia nervosa clearly have central coherence and set-shifting inefficiencies which do not significantly differ from those observed in people with anorexia nervosa. Clinically, this suggests that people with bulimia nervosa might benefit from adjunctive approaches to address these inefficiencies, such as cognitive remediation therapy.

Is there a hypothalamic basis for anorexia nervosa?

The hypothalamus has long been known to control food intake and energy metabolism through a complex network of primary and secondary neurons and glial cells. Anorexia nervosa being a complex disorder characterized by abnormal feeding behavior and food aversion, it is thus quite surprising that not much is known concerning potential hypothalamic modifications in this disorder. In this chapter, we review the recent advances in the fields of genetics, epigenetics, structural and functional imaging, and brain connectivity, as well as neuroendocrine findings and emerging animal models, which have begun to unravel the importance of hypothalamic adaptive processes to our understanding of the pathology of eating disorders.

Hypocretin (Orexin) Replacement Therapies

Twenty-two years after their discovery, the hypocretins (Hcrts), also known as orexins, are two of the most studied peptidergic systems, involved in myriad physiological systems that range from sleep, arousal, motivation, homeostatic regulation, fear, anxiety and learning. A causal relationship between activity of Hcrt and arousal stability was established shortly after their discovery and have led to the development of a new class of drugs to treat insomnia. In this review we discuss the many faces of the Hcrt system and examine recent findings that implicate decreased Hcrt function in the pathogenesis of a number of neuropsychiatric conditions. We also discuss future therapeutic strategies to replace or enhance Hcrt function as a treatment option for these neuropsychiatric conditions.

Cognitive flexibility in acute anorexia nervosa and after recovery: A systematic review

Difficulties in cognitive flexibility-the ability to adapt effectively to changes in the environment and/or changing task demands-have been reported in anorexia nervosa (AN). However, findings are inconsistent across studies and it remains unclear which specific aspects of cognitive flexibility patients with AN may struggle with. This systematic review aimed to synthesise existing research on cognitive flexibility in AN and clarify differences between patients with acute AN, patients who are weight-restored and patients who are fully recovered from AN. Electronic databases were searched through to January 2020. 3,310 papers were screened and 70 papers were included in the final review. Although adults with acute AN performed worse in perceptual flexibility tasks and self-report measures compared to HCs, they did not exhibit deficits across all domains of cognitive flexibility. Adolescents with acute AN did not differ to HCs in performance on neurocognitive tasks despite self-reporting poorer cognitive flexibility. Overall, significant differences in cognitive flexibility between acute and recovered participants was not evident, though, the findings are limited by a modest number of studies. Recovered participants performed poorer than HCs in some neurocognitive measures, however, results were inconsistent across studies. These results have implications for the assessment of cognitive flexibility in AN and targeted treatment approaches.

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.