Disruption of brain white matter microstructure in women with anorexia nervosa

Prefrontal-Limbic Circuitry Is Associated With Reward Sensitivity in Nonhuman Primates

BACKGROUND

Abnormal reward sensitivity is a risk factor for psychiatric disorders, including eating disorders such as overeating and binge-eating disorder, but the brain structural mechanisms that underlie it are not completely understood. Here, we sought to investigate the relationship between multimodal whole-brain structural features and reward sensitivity in nonhuman primates.

METHODS

Reward sensitivity was evaluated through behavioral economic analysis in which monkeys (adult rhesus macaques; 7 female, 5 male) responded for sweetened condensed milk (10%, 30%, 56%), Gatorade, or water using an operant procedure in which the response requirement increased incrementally across sessions (i.e., fixed ratio 1, 3, 10). Animals were divided into high (n = 6) or low (n = 6) reward sensitivity groups based on essential value for 30% milk. Multimodal magnetic resonance imaging was used to measure gray matter volume and white matter microstructure. Brain structural features were compared between groups, and their correlations with reward sensitivity for various stimuli was investigated.

RESULTS

Animals in the high sensitivity group had greater dorsolateral prefrontal cortex, centromedial amygdaloid complex, and middle cingulate cortex volumes than animals in the low sensitivity group. Furthermore, compared with monkeys in the low sensitivity group, high sensitivity monkeys had lower fractional anisotropy in the left dorsal cingulate bundle connecting the centromedial amygdaloid complex and middle cingulate cortex to the dorsolateral prefrontal cortex, and in the left superior longitudinal fasciculus 1 connecting the middle cingulate cortex to the dorsolateral prefrontal cortex.

CONCLUSIONS

These results suggest that neuroanatomical variation in prefrontal-limbic circuitry is associated with reward sensitivity. These brain structural features may serve as predictive biomarkers for vulnerability to food-based and other reward-related disorders.

Causal Relationship between Aging and Anorexia Nervosa: A White-Matter-Microstructure-Mediated Mendelian Randomization Analysis

This study employed a two-step Mendelian randomization analysis to explore the causal relationship between telomere length, as a marker of aging, and anorexia nervosa and to evaluate the mediating role of changes in the white matter microstructure across different brain regions. We selected genetic variants associated with 675 diffusion magnetic resonance imaging phenotypes representing changes in brain white matter. F-statistics confirmed the validity of the instruments, ensuring robust causal inference. Sensitivity analyses, including heterogeneity tests, horizontal pleiotropy tests, and leave-one-out tests, validated the results. The results show that telomere length is significantly negatively correlated with anorexia nervosa in a unidirectional manner (p = 0.017). Additionally, changes in specific white matter structures, such as the internal capsule, corona radiata, posterior thalamic radiation, left cingulate gyrus, left longitudinal fasciculus, and left forceps minor (p < 0.05), were identified as mediators. These findings enhance our understanding of the neural mechanisms, underlying the exacerbation of anorexia nervosa with aging; emphasize the role of brain functional networks in disease progression; and provide potential biological targets for future therapeutic interventions.

Assessing midbrain neuromelanin and its relationship to reward learning in anorexia nervosa: Stage 1 of a registered report

INTRODUCTION

Anorexia nervosa (AN) is a debilitating and potentially chronic eating disorder, characterized by low hedonic drive toward food, which has been linked with perturbations in both reward processing and dopaminergic activity. Neuromelanin-sensitive magnetic resonance imaging (MRI) is an emerging method to index midbrain neuromelanin-a by-product of dopaminergic synthesis. The assessment of midbrain neuromelanin, and its association with AN psychopathology and reward-related processes, may provide critical insights into reward circuit function in AN.

METHODS

This study will incorporate neuromelanin-sensitive MRI into an existing study of appetitive conditioning in those with AN. Specifically, those with acute and underweight AN (N = 30), those with weight-restored AN (N = 30), and age-matched healthy controls (N = 30) will undergo clinical assessment of current and previous psychopathology, in addition to structural neuromelanin-sensitive MRI, diffusion MRI, and functional MRI (fMRI) during appetitive conditioning.

CONCLUSION

This study will be among the first to interrogate midbrain neuromelanin in AN-a disorder characterized by altered dopaminergic activity. Results will help establish whether abnormalities in the midbrain synthesis of dopamine are evident in those with AN and are associated with symptomatic behavior and reduced ability to experience pleasure and reward.

Temperament impact on eating disorder symptoms and habit formation: a novel model to inform treatment

BACKGROUND

Temperament has long been described as the biological dimension of personality. Due to advancing brain-imaging technology, our understanding of temperament has deepened and transformed over the last 25 years. Temperament combines genetic, neurobiological and trait research. Temperament has been included peripherally in some eating disorder (ED) treatment approaches but has been ignored by most. Temperament fills a fundamental treatment gap by clarifying who is more vulnerable to develop ED and why some individuals are susceptible to specific ED symptoms while others are not. In addition, temperament targets possible treatment solutions.

MAIN TEXT

There is a need for a novel model that incorporates and explores the role of temperament in ED treatment intervention. This paper is a metaphoric temperament model to inform treatment intervention. It describes how temperament traits influences new decisions which impact new behavioural responses. In turn, it neurobiologically tracks how and why the brain efficiently transforms new decisions into new habits. This model integrates both temperament and habit research to explore (a) what temperament is; (b) how new decisions develop into habits neurobiologically; (c) that the brain wires destructive symptoms into habits in the same way that it wires healthy/productive behaviours into habits; (d) traits that trigger ED symptoms are the same traits that influence productive behaviours; and in regard to treatment implications (e) when treatment structure and intervention target client temperaments, the potential for new healthy "trait-syntonic" habits could develop.

CONCLUSIONS

This paper introduces a metaphoric model that synthesizes and integrates temperament neurobiological and trait findings with ED symptoms, habits, and client trait-based solutions. The model synthesizes and integrates different research domains to establish a brain-based foundation to inform treatment intervention. The model targets clients' temperament traits as central collections of innate self-expressions that could be utilized as tools to redirect client trait-syntonic ED responses into trait-syntonic productive outcomes. The brain bases of temperament and habit formation serve as a biological foundation for ED treatment intervention.

Attachment Trauma Is Associated with White Matter Fiber Microstructural Alterations in Adolescents with Anorexia Nervosa before and after Exposure to Psychotherapeutic and Nutritional Treatment

In the present study, we explore the role of attachment for microstructural white matter (WM) changes in adolescents with anorexia nervosa (AN) before and after exposure to short-term and nutritional treatment. The case sample consisted of 22 female adolescent inpatients with AN (mean age: 15.2 ± 1.2 years) and the control sample were 18 gender-matched healthy adolescents (mean age: 16.8 ± 0.9 years). We performed a 3T MRI in the patient group during the acute state of AN and after weight restoration (duration: 2.6 ± 1 months) and compared the data to a healthy control group. To classify attachment patterns, we used the Adult Attachment Projective Picture System. In the patient sample, over 50% were classified with an attachment trauma/unresolved attachment status. Prior to treatment exposure, fractional anisotropy (FA) reductions and concordant mean diffusivity (MD) increases were evident in the fornix, the corpus callosum and WM regions of the thalamus, which normalized in the corpus callosum and the fornix post-therapy in the total patient sample (p < 0.002). In the acute state, patients with an attachment trauma demonstrated significant FA decreases compared to healthy controls, but no MD increases, in the corpus callosum and cingulum bilaterally, which remained decreased after therapy. Attachment patterns seem to be associated with region-specific changes of WM alterations in AN.

Restlessness and an Increased Urge to Move (Drive for Activity) in Anorexia Nervosa May Strengthen Personal Motivation to Maintain Caloric Restriction and May Augment Body Awareness and Proprioception: A Lesson From Leptin Administration in Anorexia Nervosa

Anorexia nervosa (AN), a disorder of voluntary food restriction leading to severe weight loss in female adolescents, remains an enigma. In particular, the appropriation of the starved thin body into the self-concept in AN is a process insufficiently researched and still poorly understood. Healthy humans undergoing starvation experience a slowing of movements and avoid voluntary exercise. By contrast, AN tends to be not infrequently associated with voluntary, sometimes excessive and/or compulsive exercise. Such deliberate exercise, not reported in starvation, seems to be facilitated by an increased urge for movement and physical restlessness, particular to AN. The increased urge to move would reflect spontaneous daily activity, the energy expended for everything that is not sleeping, eating, or voluntary exercise. Our hypothesis is that the starvation-induced increased urge to move and restlessness may promote the development of AN. Reversal of the fasting state, by either high caloric food or by leptin administration, would be expected to reduce restlessness and the increased urge to move along with improvement in other symptoms in AN. This review explores the idea that such restless activation in AN, in itself and through accelerating body weight loss, might foster the integration of the starving body into the self-concept by (1) enhancing the person’s sense of self-control and sense of achievement and (2) through invigorating proprioception and through intensifying the perception of the changing body shape. (3) Tentative evidence from studies piloting leptin administration in chronic AN patients which support this hypothesis is reviewed. The findings show that short term administration of high doses of leptin indeed mitigated depressive feelings, inner tension, intrusive thoughts of food, and the increased urge to be physically active, easing the way to recovery, yet had little influence on the patients’ personal commitment to remain at a low weight. Full recovery then requires resolution of the individuals’ personal unresolved psychological conflicts through psychotherapy and frequently needs specialized treatment approaches to address psychiatric co-morbidities. AN might be conceptualized as a hereditary form of starvation resistance, facilitated by the effects of starvation on fitness allowing for an exceptionally intense personal commitment to perpetuate food restriction.

Neural, physiological, and psychological markers of appetitive conditioning in anorexia nervosa: a study protocol

BACKGROUND

Anorexia nervosa (AN) is a chronic and disabling psychiatric condition characterized by low hedonic drive towards food, and is thought to be inclusive of altered dimensions of reward processing. Whether there exists a fundamental aberrancy in the capacity to acquire and maintain de novo hedonic associations-a critical component of hedonic responding-has never been studied in AN.

METHODS

This multi-modal study will employ a 2-day Pavlovian appetitive conditioning paradigm to interrogate the (1) acquisition, (2) extinction, (3) spontaneous recovery and (4) reinstatement of appetitive learning in adolescents and young adults with AN. Participants will be 30 currently ill, underweight individuals with AN; 30 weight-restored individuals with AN; and 30 age-matched healthy controls, all aged 12-22 years. All subjects will undergo clinical assessment, followed by the 2-day appetitive conditioning task during which fMRI, pupillometry, heart rate deceleration, and subjective ratings will be acquired.

DISCUSSION

This study will be the first to interrogate appetitive conditioning in AN-a disorder characterized by altered hedonic responding to food. Results will help establish objective biomarkers of appetitive conditioning in AN and lay the groundwork for developing novel lines of treatment for AN and other psychiatric disorders involving diminished ability to experience pleasure and reward.

TRIAL REGISTRATION

Pending.

INTENDED REGISTRY

Clinicaltrials.gov.

Characterizing cerebral metabolite profiles in anorexia and bulimia nervosa and their associations with habitual behavior

Anorexia nervosa (AN) and bulimia nervosa (BN) are associated with altered brain structure and function, as well as increased habitual behavior. This neurobehavioral profile may implicate neurochemical changes in the pathogenesis of these illnesses. Altered glutamate, myo-inositol and N-acetyl aspartate (NAA) concentrations are reported in restrictive AN, yet whether these extend to binge-eating disorders, or relate to habitual traits in affected individuals, remains unknown. We therefore used single-voxel proton magnetic resonance spectroscopy to measure glutamate, myo-inositol, and NAA in the right inferior lateral prefrontal cortex and the right occipital cortex of 85 women [n = 22 AN (binge-eating/purging subtype; AN-BP), n = 33 BN, n = 30 controls]. To index habitual behavior, participants performed an instrumental learning task and completed the Creature of Habit Scale. Women with AN-BP, but not BN, had reduced myo-inositol and NAA concentrations relative to controls in both regions. Although patient groups had intact instrumental learning task performance, both groups reported increased routine behaviors compared to controls, and automaticity was related to reduced prefrontal glutamate and NAA participants with AN-BP. Our findings extend previous reports of reduced myo-inositol and NAA levels in restrictive AN to AN-BP, which may reflect disrupted axonal-glial signaling. Although we found inconsistent support for increased habitual behavior in AN-BP and BN, we identified preliminary associations between prefrontal metabolites and automaticity in AN-BP. These results provide further evidence of unique neurobiological profiles across binge-eating disorders.

White matter integrity is disrupted in adolescents with acute anorexia nervosa: A diffusion tensor imaging study

Anorexia nervosa (AN) is a highly debilitating mental illness with multifactorial etiology. It oftentimes begins in adolescence, therefore understanding the pathophysiology in this period is important. Few studies investigated the possible impact of the acute state of illness on white matter (WM) tissue properties in the developing adolescent brain. The present study expands our understanding of the implications of AN and starvation on WM integrity. 67 acutely ill adolescent patients suffering from AN restricting type were compared with 32 healthy controls using diffusion tensor imaging assessing fractional anisotropy (FA) and mean diffusivity (MD). We found widespread alterations in the vast majority of the WM regions with significantly decreased FA and increased MD in the AN group. In this highly selective sample in the acute stage of AN, the alterations are likely to be the consequence of starvation. Still, we cannot rule out that some of the affected regions might play a key role in AN-specific psychopathology.

Initial evidence of abnormal brain plasticity in anorexia nervosa: an ultra-high field study

Anorexia Nervosa has been associated with white matter abnormalities implicating subcortical abnormal myelination. Extending these findings to intracortical myelin has been challenging but ultra-high field neuroimaging offers new methodological opportunities. To test the integrity of intracortical myelin in AN we used 7 T neuroimaging to acquire T1-weighted images optimized for intracortical myelin from seven females with AN (age range: 18-33) and 11 healthy females (age range: 23-32). Intracortical T₁ values (inverse index of myelin concentration) were extracted from 148 cortical regions at ten depth-levels across the cortical ribbon. Across all cortical regions, these levels were averaged to generate estimates of total intracortical myelin concentration and were clustered using principal component analyses into two clusters; the outer cluster comprised T₁ values across depth-levels ranging from the CSF boundary to the middle of the cortical regions and the inner cluster comprised T₁ values across depth-levels ranging from the middle of the cortical regions to the gray/white matter boundary. Individuals with AN exhibited higher T₁ values (i.e., decreased intracortical myelin concentration) in all three metrics. It remains to be established if these abnormalities result from undernutrition or specific lipid nutritional imbalances, or are trait markers; and whether they may contribute to neurobiological deficits seen in AN.

White matter microstructural differences in underweight adolescents with anorexia nervosa and a preliminary longitudinal investigation of change following short-term weight restoration

PURPOSE

Anorexia nervosa (AN) affects approximately 2.9% of females and has the highest mortality rate among all psychiatric disorders. Despite several advances, the neurobiology of this disorder is still not well understood. Several studies have reported abnormalities in the white matter, but it is not know if these are disease-related or secondary to undernutrition. This study aimed to further our understanding of white matter pathology using diffusion-weighted imaging in underweight adolescents with AN, and to examine changes occurring after short-term weight restoration.

METHODS

Analyses were conducted on diffusion-weighted imaging from 24 female adolescents with AN and 17 age- and gender-matched healthy controls (HC), aged 14-19 years. Groups were compared on fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) using tract-based spatial statistics analysis and DTI measures were correlated with eating disorder examination questionnaire (EDE-Q) subscales and body mass index (BMI). Preliminary repeated-measure analyses were also conducted on eight participants after short-term weight restoration (median 41 days).

RESULTS

Widespread increases in MD of up to 9% were found in underweight AN relative to HC, particularly in the corpus callosum. This was associated with both increased AD and RD, suggestive of dys- or de-myelination. There were no significant group differences in FA, and no significant correlations between DTI measures, BMI or EDE-Q subscale score. Weight restoration therapy significantly reduced MD, to levels significantly lower than HC, but did not consistently alter FA across individuals.

CONCLUSIONS

White matter microstructure is significantly altered in female adolescents with AN, with preliminary longitudinal data suggesting that it may be reversible with short-term weight restoration.

LEVEL OF EVIDENCE

Level III: evidence obtained from well-designed cohort or case-control analytic studies.

White matter microstructure in women with acute and remitted anorexia nervosa: an exploratory neuroimaging study

Anorexia nervosa (AN) is a highly heritable psychiatric disorder characterized by starvation and emaciation and associated with changes in brain structure. The precise nature of these changes remains unclear, as does their developmental time course and capacity for reversal with weight restoration. In this exploratory neuroimaging study, we sought to characterize changes in white matter microstructure in women with acute and remitted AN. Diffusion-weighted MRI data was collected from underweight women with a current diagnosis of AN (acAN: n = 23), weight-recovered women with a past diagnosis of AN (recAN: n = 23), and age-matched healthy control women (HC: n = 24). Image processing and analysis were performed with Tract-Based Spatial Statistics, part of FSL, and group differences in voxelwise, brain-wide fractional anisotropy (FA) and mean diffusivity (MD), indices of white matter microstructure, were tested with nonparametric permutation and threshold-free cluster enhancement. No significant main effect of group on FA was identified. A significant main effect of group on MD was observed in a large cluster covering 9.2% of white matter and including substantial portions of the corpus callosum, corona radiata, internal capsule, and superior longitudinal fasciculus, and post hoc analyses revealed similar effects of group on axial diffusivity (AD) and radial diffusivity (RD). Clusterwise MD was significantly higher in acAN participants (+3.8%) and recAN participants (+2.9%) than healthy controls, and the same was true for clusterwise AD and RD. Trait-based increases in diffusivity, changes in which have been associated with atypical myelination and impaired axon integrity, suggest a link between altered white matter microstructure and vulnerability to AN, and evidence of reduced oligodendrocyte density in AN provides further support for this hypothesis. Potential mechanisms of action include atypical neurodevelopment and systemic inflammation.

Neuroimaging Findings in Adolescents and Young Adults with Anorexia Nervosa: A Systematic Review

BACKGROUND

Anorexia nervosa (AN) is a serious, multifactorial mental disorder affecting predominantly young females. This systematic review examines neuroimaging findings in adolescents and young adults up to 24 years old, in order to explore alterations associated with disease pathophysiology.

METHODS

Eligible studies on structural and functional brain neuroimaging were sought systematically in PubMed, CENTRAL and EMBASE databases up to 5 October 2020.

RESULTS

Thirty-three studies were included, investigating a total of 587 patients with a current diagnosis of AN and 663 healthy controls (HC). Global and regional grey matter (GM) volume reduction as well as white matter (WM) microstructure alterations were detected. The mainly affected regions were the prefrontal, parietal and temporal cortex, hippocampus, amygdala, insula, thalamus and cerebellum as well as various WM tracts such as corona radiata and superior longitudinal fasciculus (SLF). Regarding functional imaging, alterations were pointed out in large-scale brain networks, such as default mode network (DMN), executive control network (ECN) and salience network (SN). Most findings appear to reverse after weight restoration. Specific limitations of neuroimaging studies in still developing individuals are also discussed.

CONCLUSIONS

Structural and functional alterations are present in the early course of the disease, most of them being partially or totally reversible. Nonetheless, neuroimaging findings have been open to many biological interpretations. Thus, more studies are needed to clarify their clinical significance.

Hippocampal volume, function, and related molecular activity in anorexia nervosa: A scoping review

INTRODUCTION

Anorexia nervosa (AN) is a serious and persistent eating disorder, characterized by severe dietary restriction and weight loss, with a third of patients developing a  severe-enduring form. The factors contributing to this progression are poorly understood, although there is evidence for impairments in neural structures such as the hippocampus, an area particularly affected by malnutrition and chronic stress.

AREAS COVERED

This study aimed to map the evidence for alterations in hippocampal volume, function, and related molecular activity in anorexia nervosa. PubMed, PsycINFO, and Web of Science were searched for studies related to hippocampal function and integrity using a range of methodologies, such as neuropsychological paradigms, structural and functional magnetic resonance imaging, and analysis of blood components.

EXPERT OPINION

Thirty-nine studies were included in this review. The majority were neuroimaging studies, which found hippocampus-specific volumetric and functional impairments. Neuropsychological studies showed evidence for a specific memory and learning impairments. There was some evidence for molecular abnormalities (e.g. cortisol), although these were few studies. Taken together, our review suggests that the hippocampus might be a particular region of interest when considering neurobiological approaches to understanding AN. These findings warrant further investigation and may lead to novel treatment approaches.

Developmental stage-dependent relationships between ghrelin levels and hippocampal white matter connections in low-weight anorexia nervosa and atypical anorexia nervosa

INTRODUCTION

Disruptions in homeostatic and hedonic food motivation are proposed to underlie anorexia nervosa (AN) and atypical AN, restrictive eating disorders which commonly onset in puberty. Ghrelin, a neuroprotective hormone that drives hedonic eating is increased in AN and is expressed in the hippocampus. White matter (WM) undergoes significant change during puberty in regions involved in food motivation, particularly WM tracts connected with the hippocampus. The association between ghrelin and WM region of interest (ROI) with hippocampal connections in restrictive eating disorders, particularly in adolescence during key neurodevelopmental growth, is unknown.

METHODS

We evaluated fasting plasma ghrelin and WM microstructure (measured by free-water corrected fractional anisotropy (FA-t)) in WM ROIs with hippocampal connections - the fornix and the hippocampal portion of the cingulum - in 56 adolescent females (age range: 11.9 - 22.1 y; mean: 19.0 y) with low-weight eating disorders including AN and atypical AN (N = 36) and healthy controls (N = 20).

RESULTS

FA-t in the fornix or hippocampal portion of the fornix did not differ between groups. Ghrelin was higher in AN/atypical AN vs. HC and was positively correlated with puberty stage in the AN/atypical AN group, but not the HC group. The correlation between ghrelin and FA-t in the fornix was significantly different in females with AN/atypical AN compared to controls. In AN/atypical AN, pubertal stage moderated the relation between fasting plasma ghrelin and FA-t in the fornix: higher fasting ghrelin was associated with lower FA-t in the fornix in late-post-puberty, but was not associated with FA-t in the early to mid stages of puberty.

CONCLUSIONS

In post-pubertal females with low-weight AN/atypical AN, higher levels of ghrelin are associated with lower FA-t in the fornix. This relationship is not evident in the early to mid stages of puberty in AN/atypical AN or in HC, and may reflect a lack of possible neuroprotective effects of ghrelin in late-post puberty only. Understanding the effects of ghrelin on WM microstructure longitudinally and following recovery from AN/Atypical AN and how this differs across pubertal stages will be an important next step. These findings could ultimately inform treatment staging and aid in diagnosis and detection of AN/atypical AN.

Multimodal neuroimaging in anorexia nervosa

Anorexia nervosa (AN) is a severe and complex psychiatric disorder characterized by intense fear about weight gain and finalized to food-related control behaviors. Growing interest has been demonstrated about neurobiological processes subtend to AN physiopathology. The present review aimed to collect neurostructural and neurofunctional available data from 2010 to 2019. Results have been organized according to the neuroimaging technique employed, also including a specific section on electroencephalographic results, mostly neglected in previous reviews. Diffuse cerebral vulnerability has been demonstrated and the contribution of several structures has been identified. Insula, cingulate cortex, parietal and frontal areas are primarily involved both by structural and functional perspectives. Moreover, consistent alterations in white matter integrity and brain electrical activity have been reported. Neuroimaging findings give a substantial contribution to AN pathophysiological description, also in order to understand altered but reversible processes in the passage from acute illness phase to disorder's remission, useful also for defining therapy.

Cortical thickness, local gyrification index and fractal dimensionality in people with acute and recovered Anorexia Nervosa and in people with Bulimia Nervosa

Eating disorders (EDs) have a possible neurodevelopmental pathogenesis. Our study aim was to assess regional cortical thickness (CT), local gyrification index (lGI) and fractal dimensionality (FD), as specific markers of cortical neurodevelopment in ED females. Twenty-two women with acute anorexia nervosa (acuAN), 10 with recovered anorexia nervosa (recAN), 24 with bulimia nervosa (BN) and 35 female healthy controls (HC) underwent a 3T MRI scan. All data were processed by FreeSurfer. Compared to recAN group women with acuAN showed a lower CT in multiple areas, while compared to HC they showed lower CT in temporal regions. BN group showed higher CT values in temporal and paracentral areas compared to HC. In multiple cortical areas, AcuAN group showed greater values of lGI compared to recAN group and lower values of lGI compared to HC. The BN group showed lower lGI in left medial orbitofrontal cortex compared to HC. No significant differences were found in FD among the groups. Present results provide evidence of CT and lGI alterations in patients with AN and, for the first time, in those with BN. Although these alterations could be state-dependent phenomena, they may underlie psychopathological aspects of EDs.

Moving towards specificity: A systematic review of cue features associated with reward and punishment in anorexia nervosa

Models of anorexia nervosa (AN) posit that symptoms are maintained through deficient reward and enhanced punishment processing. However, theoretical and empirical inconsistencies highlight the need for a more nuanced conceptualization of this literature. Our goal was to comprehensively review the research on reward and punishment responding in AN from a cue-specific lens to determine which stimuli evoke or discourage reward and punishment responses in this population, and, ultimately, what properties these rewarding and punishing cues might share. A systematic review interrogating reward and punishment responses to specific cues yielded articles (n = 92) that examined responses to disorder relevant (e.g., food) and irrelevant (e.g., money) stimuli across self-report, behavioral, and biological indices. Overall, in most studies individuals with AN exhibited aversive responses to cues signaling higher body weights, social contexts, and monetary losses, and appetitive responses to cues for weight loss behaviors and thinness. Findings were more mixed on responses to palatable food and monetary gains. Results highlight that reward and punishment responding in AN are context specific and may be affected by varied stimulus qualities (e.g., predictability, controllability, delay, effort). Increasing specificity in future research on reward and punishment mechanisms in AN will better inform development of precisely-targeted interventions.

Age influences structural brain restoration during weight gain therapy in anorexia nervosa

Neuroimaging studies on anorexia nervosa (AN) have consistently reported globally reduced gray matter in patients with acute AN. While first studies on adolescent AN patients provide evidence for the reversibility of these impairments after weight gain, longitudinal studies with detailed regional analysis for adult AN patients are lacking and factors associated with brain restitution are poorly understood. We investigated structural changes in anorexia nervosa using T1-weighted magnetic resonance images with surface-based morphometry. The sample consisted of 26 adult women with severe AN and 30 healthy controls. The longitudinal design comprised three time points, capturing the course of weight-restoration therapy in AN patients at distinct stages of weight gain (BMI ≤ 15.5 kg/m²; 15.5 < BMI < 17.5 kg/m²; BMI ≥ 17.5 kg/m²). Compared to controls, AN patients showed globally decreased cortical thickness and subcortical volumes at baseline. Linear mixed effect models revealed the reversibility of these alterations, with brain restoration being most pronounced during the first half of treatment. The restoration of cortical thickness of AN patients negatively correlated with age, but not duration of illness. After weight restoration, residual group differences of cortical thickness remained in the superior frontal cortex. These findings indicate that structural brain alterations of adult patients with severe AN recuperate independently of the duration of illness during weight-restoration therapy. The temporal pattern of brain restoration suggests a decrease in restoration rate over the course of treatment, with patients' age as a strong predictor of brain restitution, possibly reflecting decreases of brain plasticity as patients grow older.

The effect of the demyelinating agent cuprizone on binge-like eating of sweetened palatable food in female and male C57BL/6 substrains

Binge eating is a heritable symptom of eating disorders with an unknown genetic etiology. Rodent models for binge-like eating (BLE) of palatable food permit the study of genetic and biological mechanisms. We previously genetically mapped a coding mutation in Cyfip2 associated with increased BLE of sweetened palatable food in the C57BL/6NJ versus C57BL/6J substrain. The increase in BLE in C57BL/6NJ mice was associated with a decrease in transcription of genes enriched for myelination in the striatum. Here, we tested the hypothesis that decreasing myelin levels with the demyelinating agent cuprizone would enhance BLE. Mice were treated with a 0.3% cuprizone home cage diet for two weeks. Cuprizone induced similar weight loss in both substrains and sexes that recovered within 48 h after removal of cuprizone. Following a three-week recovery period, mice were trained for BLE in an intermittent, limited access procedure. Surprisingly, cuprizone significantly reduced BLE in male but not female C57BL/6NJ mice while having no effect in C57BL/6J mice. Cuprizone also reduced myelin basic protein (MBP) at seven weeks post-cuprizone removal while having no effect on myelin-associated glycoprotein at this time point. C57BL/6NJ mice also showed less MBP than C57BL/6J mice. There were no statistical interactions of Treatment with Sex on MBP levels, indicating that differences in MBP reduction are unlikely to account for sex differences in BLE. To summarize, cuprizone induced an unexpected, significant reduction in BLE in C57BL/6NJ males, which could indicate genotype-dependent sex differences in the biological mechanisms of BLE.

White Matter Abnormalities in Anorexia Nervosa: Psychoradiologic Evidence From Meta-Analysis of Diffusion Tensor Imaging Studies Using Tract Based Spatial Statistics

Background: Anorexia nervosa (AN) is a debilitating illness whose neural basis remains unclear. Studies using tract-based spatial statistics (TBSS) with diffusion tensor imaging (DTI) have demonstrated differences in white matter (WM) microarchitecture in AN, but the findings are inconclusive and controversial.

Objectives: To identify the most consistent WM abnormalities among previous TBSS studies of differences in WM microarchitecture in AN.

Methods: By systematically searching online databases, a total of 11 datasets were identified, including 245 patients with AN and 246 healthy controls (HC). We used Seed-based d Mapping to analyze fractional anisotropy (FA) differences between AN patients and HC, and performed meta-regression analysis to explore the effects of clinical characteristics on WM abnormalities in AN.

Results: The pooled results of all AN patients showed robustly lower FA in the corpus callosum (CC) and the cingulum compared to HC. These two regions preserved significance in the sensitivity analysis as well as in all subgroup analyses. Fiber tracking showed that the WM tracts primarily involved were the body of the CC and the cingulum bundle. Meta-regression analysis revealed that the body mass index and mean age were not linearly correlated with the lower FA.

Conclusions: The most consistent WM microstructural differences in AN were in the interhemispheric connections and limbic association fibers. These common “targets” advance our understanding of the complex neural mechanisms underlying the puzzling symptoms of AN, and may help in developing early treatment approaches.

Anorexia nervosa and diffusion weighted imaging: An open methodological question raised by a systematic review and a fractional anisotropy anatomical likelihood estimation meta-analysis

BACKGROUND

Anorexia nervosa (AN) is characterized by white matter abnormalities in neuroimaging studies. Fractional anisotropy (FA) is a diffusion tensor imaging (DTI) index that is considered an instrument for the evaluation of white matter alterations. However, the literature has recently pointed out the role of the partial volume effect (PVE) as a confounding factor for the identification of juxtaposed tissues. Our goal was to review the DTI literature in AN and evaluate possible confounding factors linked to the reported results.

METHOD

A systematic review of the literature was conducted to identify Diffusion Tensor Imaging studies of individuals with AN and, subsequently, an anatomical likelihood estimation (ALE) meta-analysis was performed on studies published before March 18, 2019.

RESULTS

Twenty-four studies (AN = 517, controls = 542) were included in the qualitative systematic review of the literature. Ten published studies underwent the ALE-analysis (AN = 210, controls = 229), plus data from an unpublished cohort (AN = 38, controls = 38). Two clusters of decreased FA were identified, namely in the left corona radiata, and in the left thalamus. Only one article took the PVE correction analysis into account.

CONCLUSIONS

The alterations identified must be considered within the limits of a possible methodological bias regarding PVE and free water and re-analysis of the data may be recommended. The preliminary data showed that the alteration of white matter pathways between the limbic structures and brain cortex may be linked to the processing of somatosensory information that could play a key role in the psychopathology of the disorder.

Altered thalamo–cortical and occipital–parietal– temporal–frontal white matter connections in patients with anorexia and bulimia nervosa: a systematic review of diffusion tensor imaging studies

BACKGROUND

Anorexia nervosa and bulimia nervosa are complex mental disorders, and their etiology is still not fully understood. This paper reviews the literature on diffusion tensor imaging studies in patients with anorexia nervosa and bulimia nervosa to explore the usefulness of white matter microstructural analysis in understanding the pathophysiology of eating disorders.

METHODS

We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify diffusion tensor imaging studies that compared patients with an eating disorder to control groups. We searched relevant databases for studies published from database inception to August 2018, using combinations of select keywords. We categorized white matter tracts according to their 3 main classes: projection (i.e., thalamo–cortical), association (i.e., occipital–parietal–temporal–frontal) and commissural (e.g., corpus callosum).

RESULTS

We included 19 papers that investigated a total of 427 participants with current or previous eating disorders and 444 controls. Overall, the studies used different diffusion tensor imaging approaches and showed widespread white matter abnormalities in patients with eating disorders. Despite differences among the studies, patients with anorexia nervosa showed mainly white matter microstructural abnormalities of thalamo–cortical tracts (i.e., corona radiata, thalamic radiations) and occipital–parietal–temporal–frontal tracts (i.e., left superior longitudinal and inferior fronto-occipital fasciculi). It was less clear whether white matter alterations persist after recovery from anorexia nervosa. Available data on bulimia nervosa were partially similar to those for anorexia nervosa.

LIMITATIONS

Study sample composition and diffusion tensor imaging analysis techniques were heterogeneous. The number of studies on bulimia nervosa was too limited to be conclusive.

CONCLUSION

White matter microstructure appears to be affected in anorexia nervosa, and these alterations may play a role in the pathophysiology of this eating disorder. Although we found white matter alterations in bulimia nervosa that were similar to those in anorexia nervosa, white matter changes in bulimia nervosa remain poorly investigated, and these findings were less conclusive. Further studies with longitudinal designs and multi-approach analyses are needed to better understand the role of white matter changes in eating disorders.

White Matter Abnormalities in the Corpus Callosum in Acute and Recovered Anorexia Nervosa Patients-A Diffusion Tensor Imaging Study

Objective: Severe malnutrition in patients with anorexia nervosa (AN) as well as possible trait-related aberrations lead to pronounced structural brain changes whose reversibility after recovery is currently unclear. Previous diffusion tensor imaging (DTI) studies investigating white matter (WM) microstructure alterations in AN are inconsistent. Methods: In this so far largest DTI study in adults, we investigated 33 AN patients, 20 recovered (REC), and 33 healthy women. DTI data were processed using the "DTI and Fiber tools," and the Computational Anatomy Toolbox. WM integrity, both in terms of fractional anisotropy (FA) and mean diffusivity (MD), was assessed. Results: We found a significant FA decrease in the corpus callosum (body) and an MD decrease in the posterior thalamic radiation in the AN group. The REC group displayed FA decrease in the corpus callosum in comparison to HC, whereas there were no MD differences between the REC and HC groups. Conclusion: Despite prolonged restoration of weight in the REC group, no significant regeneration of WM integrity in terms of FA could be observed. Transient changes in MD likely represent a reversible consequence of the acute state of starvation or result from dehydration. Reduction of FA either may be due to WM damage resulting from malnutrition or may be considered a pre-morbid marker.

Dynamic changes in white matter microstructure in anorexia nervosa: findings from a longitudinal study

BACKGROUND

Gray matter (GM) 'pseudoatrophy' is well-documented in patients with anorexia nervosa (AN), but changes in white matter (WM) are less well understood. Here we investigated the dynamics of microstructural WM brain changes in AN patients during short-term weight restoration in a combined longitudinal and cross-sectional study design.

METHODS

Diffusion-weighted images were acquired in young AN patients before (acAN-Tp1, n = 56) and after (acAN-Tp2, n = 44) short-term weight restoration as well as in age-matched healthy controls (HC, n = 60). Images were processed using Tract-Based-Spatial-Statistics to compare fractional anisotropy (FA) across groups and timepoints.

RESULTS

In the cross-sectional comparison, FA was significantly reduced in the callosal body in acAN-Tp1 compared with HC, while no differences were found between acAN-Tp2 and HC. In the longitudinal arm, FA increased with weight gain in acAN-Tp2 relative to acAN-Tp1 in large parts of the callosal body and the fornix, while it decreased in the right corticospinal tract.

CONCLUSIONS

Our findings reveal that dynamic, bidirectional changes in WM microstructure in young underweight patients with AN can be reversed with brief weight restoration therapy. These results parallel those previously observed in GM and suggest that alterations in WM in non-chronic AN are also state-dependent and rapidly reversible with successful intervention.

Possible Neurobiological Underpinnings of Homosexuality and Gender Dysphoria

Although frequently discussed in terms of sex dimorphism, the neurobiology of sexual orientation and identity is unknown. We report multimodal magnetic resonance imaging data, including cortical thickness (Cth), subcortical volumes, and resting state functional magnetic resonance imaging, from 27 transgender women (TrW), 40 transgender men (TrM), and 80 heterosexual (40 men) and 60 homosexual cisgender controls (30 men). These data show that whereas homosexuality is linked to cerebral sex dimorphism, gender dysphoria primarily involves cerebral networks mediating self-body perception. Among the homosexual cisgender controls, weaker sex dimorphism was found in white matter connections and a partly reversed sex dimorphism in Cth. Similar patterns were detected in transgender persons compared with heterosexual cisgender controls, but the significant clusters disappeared when adding homosexual controls, and correcting for sexual orientation. Instead, both TrW and TrM displayed singular features, showing greater Cth as well as weaker structural and functional connections in the anterior cingulate-precuneus and right occipito-parietal cortex, regions known to process own body perception in the context of self.

White matter alterations in anorexia nervosa: Evidence from a voxel-based meta-analysis

Anorexia nervosa (AN) is a severe psychiatric disorder with a complex and poorly understood etiology. Recent studies have sought to investigate differences in white matter microstructure in AN, with significant results in several brain regions. A systematic literature search of Embase, PubMed and Psychinfo databases was conducted in order to identify Diffusion Tensor Imaging (DTI) studies of patients with AN and controls. We performed a meta-analysis of studies that met our inclusion criteria (N = 13) using effect size-signed differential mapping (AES-SDM) to detect differences in Fractional Anisotropy (FA) in patients with AN (N = 227) compared to healthy controls (N = 243). The quantitative meta-analysis of DTI studies identified decreased FA in the posterior areas of the corpus callosum, the left superior longitudinal fasciculus II, and the left precentral gyrus, as well as increased FA in the right cortico-spinal projections, and lingual gyrus in AN vs. controls. Studies of WM architecture are still limited in AN; further studies with longitudinal design are needed to better understand the complexity of abnormalities, and their persistence.

Recovery of cortical volume and thickness after remission from acute anorexia nervosa

OBJECTIVE

Reduced grey (GM) and white matter (WM) volumes and increased cerebrospinal fluid (CSF) have been frequently reported in anorexia nervosa (AN), but studies focusing on cortical thickness (CT) are scarce and findings inconsistent. We conducted the first study in AN that analyzed both parameters in the same study to gain novel and comprehensive insight.

METHOD

Voxel-based morphometry (VBM) analysis was performed on T1-weighted magnetic resonance images from 34 predominantly adult women with acute AN, 24 REC participants, and 41 healthy controls (HC). Global brain segment volumes (GM, WM, and CSF), regional GM volume, and cortical thickness measures were obtained from the same study sample. We further focused on recovery by including a REC group.

RESULTS

The GM and WM volumes were decreased, and correspondingly, the CSF volume increased in the AN in comparison to the HC and REC groups. No significant volume differences between the REC and HC groups could be observed. AN patients showed reduced regional GM volumes in the right hippocampus and the left middle and right inferior frontal gyrus. Cortical thinning occurred in the AN group, which was particularly robust in fronto-parietal areas. The REC and HC groups failed to show any regional GM or cortical thickness differences.

DISCUSSION

AN is accompanied by severe loss of brain volume and cortical thickness as assessed by complementary investigation tools. However, these changes seem to be largely reversible, which should be encouraging for therapists and patients. The underlying neurobiological mechanisms remain unclear and should be assessed in further studies.

White matter microstructure in anorexia nervosa

The neurobiological underpinnings of anorexia nervosa (AN) are unclear. White matter deficits have been described in the illness, but findings are inconsistent between studies. The aim of this study was to investigate differences in white matter microstructure in AN using diffusion-weighted imaging (DWI). It was hypothesised that people with AN, relative to a healthy control (HC) group, would show decreased functional anisotropy (FA) and increased mean diffusivity (MD) in the fornix and superior longitudinal fasciculus, consistent with previous literature. Analyses were conducted on 23 females with AN and 26 age- and gender-matched HCs using tract-based spatial statistics (TBSS). The results revealed widespread FA decreases and MD increases in the AN group. Our hypothesis was largely supported, although FA differences were not specifically found in the fornix. The findings suggest extensive differences in white matter structure in AN, which may contribute to AN pathophysiology.

Subcortical volume and cortical surface architecture in women with acute and remitted anorexia nervosa: An exploratory neuroimaging study

BACKGROUND

Anorexia nervosa (AN) is a highly heritable psychiatric disorder characterized by starvation and emaciation and associated with changes in brain structure. The precise nature of these changes remains unclear, as does their developmental time course and capacity for reversal with weight-restoration. In this comprehensive neuroimaging study, we sought to characterize these changes by measuring subcortical volume and cortical surface architecture in women with acute and remitted AN.

METHODS

Structural magnetic resonance imaging data was acquired from underweight women with a current diagnosis of AN (acAN: n = 23), weight-recovered women with a past diagnosis of AN (recAN: n = 24), and female controls (HC: n = 24). Subcortical segmentation and cortical surface reconstruction were performed with FreeSurfer 6.0.0, and group differences in regional volume and vertex-wise, cortex-wide thickness, surface area, and local gyrification index (LGI), a measure of folding, were tested with separate univariate analyses of covariance.

RESULTS

Mean hippocampal and thalamic volumes were significantly reduced in acAN participants, as was mean cortical thickness in four frontal and temporal clusters. Mean LGI was significantly reduced in acAN and recAN participants in five frontal and parietal clusters. No significant group differences in cortical surface area were detected.

CONCLUSIONS

Reductions in subcortical volume, cortical thickness, and right postcentral LGI were unique to women with acute AN, indicating state-dependence and pointing towards cellular remodeling and sulcal widening as consequences of disease manifestation. Reductions in bilateral frontal LGI were observed in women with acute and remitted AN, suggesting a role of atypical neurodevelopment in disease vulnerability.

Self and other body perception in anorexia nervosa: The role of posterior DMN nodes

OBJECTIVES

Body image distortion is a core symptom of anorexia nervosa (AN), which involves alterations in self- (and other's) evaluative processes arising during body perception. At a neural level, self-related information is thought to rely on areas of the so-called default mode network (DMN), which, additionally, shows prominent synchronised activity at rest.

METHODS

Twenty female patients with AN and 20 matched healthy controls were scanned using magnetic resonance imaging when: (a) viewing video clips of their own body and another's body; (b) at rest. Between-group differences within the DMN during task performance were evaluated and further explored for task-related and resting-state-related functional connectivity alterations.

RESULTS

AN patients showed a hyperactivation of the dorsal posterior cingulate cortex during their own-body processing but a response failure to another's body processing at the precuneus and ventral PCC. Increased task-related connectivity was found between dPCC-dorsal anterior cingulate cortex and precuneus-mid-temporal cortex. Further, AN patients showed decreased resting-state connectivity between the dPCC and the angular gyrus.

CONCLUSIONS

The PCC and the precuneus are suggested as key components of a network supporting self-other-evaluative processes implicated in body distortion, while the existence of DMN alterations at rest might reflect a sustained, task-independent breakdown within this network in AN.

Structural Neuroimaging of Anorexia Nervosa: Future Directions in the Quest for Mechanisms Underlying Dynamic Alterations

Anorexia nervosa (AN) is a serious eating disorder characterized by self-starvation and extreme weight loss. Pseudoatrophic brain changes are often readily visible in individual brain scans, and AN may be a valuable model disorder to study structural neuroplasticity. Structural magnetic resonance imaging studies have found reduced gray matter volume and cortical thinning in acutely underweight patients to normalize following successful treatment. However, some well-controlled studies have found regionally greater gray matter and persistence of structural alterations following long-term recovery. Findings from diffusion tensor imaging studies of white matter integrity and connectivity are also inconsistent. Furthermore, despite the severity of AN, the number of existing structural neuroimaging studies is still relatively low, and our knowledge of the underlying cellular and molecular mechanisms for macrostructural brain changes is rudimentary. We critically review the current state of structural neuroimaging in AN and discuss the potential neurobiological basis of structural brain alterations in the disorder, highlighting impediments to progress, recent developments, and promising future directions. In particular, we argue for the utility of more standardized data collection, adopting a connectomics approach to understanding brain network architecture, employing advanced magnetic resonance imaging methods that quantify biomarkers of brain tissue microstructure, integrating data from multiple imaging modalities, strategic longitudinal observation during weight restoration, and large-scale data pooling. Our overarching objective is to motivate carefully controlled research of brain structure in eating disorders, which will ultimately help predict therapeutic response and improve treatment.

Preserved white matter microstructure in young patients with anorexia nervosa?

A massive but reversible reduction of cortical thickness and subcortical gray matter (GM) volumes in Anorexia Nervosa (AN) has been recently reported. However, the literature on alterations in white matter (WM) volume and microstructure changes in both acutely underweight AN (acAN) and after recovery (recAN) is sparse and results are inconclusive. Here, T1-weighted and diffusion-weighted MRI data in a sizable sample of young and medication-free acAN (n = 35), recAN (n = 32), and age-matched female healthy controls (HC, n = 62) were obtained. For analysis, a well-validated global probabilistic tractography reconstruction algorithm including rigorous motion correction implemented in FreeSurfer: TRACULA (TRActs Constrained by UnderLying Anatomy) were used. Additionally, a clustering algorithm and a multivariate pattern classification technique to WM metrics to predict group membership were applied. No group differences in either WM volume or WM microstructure were detected with standard analysis procedures either in acAN or recAN relative to HC after controlling for the number of performed statistical tests. These findings were not affected by age, IQ, or psychiatric symptoms. While cluster analysis was unsuccessful at discriminating between groups, multivariate pattern classification showed some ability to separate acAN from HC (but not recAN from HC). However, these results were not compatible with a straightforward hypothesis of impaired WM microstructure. The current findings suggest that WM integrity is largely preserved in non-chronic AN. This finding stands in contrast to findings in GM, but may help to explain the relatively intact cognitive performance of young patients with AN and provide the basis for the fast recovery of GM structures. Hum Brain Mapp 37:4069-4083, 2016. © 2016 Wiley Periodicals, Inc.

Abnormal reward circuitry in anorexia nervosa: A longitudinal, multimodal MRI study

Anorexia nervosa (AN) is a debilitating illness and existing interventions are only modestly effective. This study aimed to determine whether AN pathophysiology is associated with altered connections within fronto-accumbal circuitry subserving reward processing. Diffusion and resting-state functional MRI scans were collected in female inpatients with AN (n = 22) and healthy controls (HC; n = 18) between the ages of 16 and 25 years. Individuals with AN were scanned during the acute, underweight phase of the illness and again following inpatient weight restoration. HC were scanned twice over the same timeframe. Based on univariate and multivariate analyses of fronto-accumbal circuitry, underweight individuals with AN were found to have increased structural connectivity (diffusion probabilistic tractography), increased white matter anisotropy (tract-based spatial statistics), increased functional connectivity (seed-based correlation in resting-state fMRI), and altered effective connectivity (spectral dynamic causal modeling). Following weight restoration, fronto-accumbal structural connectivity continued to be abnormally increased bilaterally with large (partial η²  = 0.387; right NAcc-OFC) and moderate (partial η²  = 0.197; left NAcc-OFC) effect sizes. Increased structural connectivity within fronto-accumbal circuitry in the underweight state correlated with severity of eating disorder symptoms. Taken together, the findings from this longitudinal, multimodal neuroimaging study offer converging evidence of atypical fronto-accumbal circuitry in AN. Hum Brain Mapp 37:3835-3846, 2016. © 2016 Wiley Periodicals, Inc.

Normal white matter microstructure in women long-term recovered from anorexia nervosa: A diffusion tensor imaging study

OBJECTIVES

Studies point to white matter (WM) microstructure alterations in both adolescent and adult patients with anorexia nervosa (AN). These include reduced fractional anisotropy in several WM fiber tracts, suggesting reduced WM integrity. The extent to which these alterations are reversible with recovery from AN is unclear. There is a paucity of research investigating the presence of WM microstructure alterations in recovered AN patients, and results are inconsistent. This study aimed to investigate the presence of WM microstructure alterations in women long-term recovered from AN.

METHOD

Twenty-one adult women who were recovered from AN for at least 1 year were compared to 21 adult comparison women. Participants were recruited via user-organizations for eating disorders, local advertisements, and online forums. Diffusion tensor imaging was used to compare WM microstructure between groups. Correlations between WM microstructure and clinical characteristics were also explored.

RESULTS

There were no statistically significant between-group differences in WM microstructure. These null findings remained when employing liberal alpha level thresholds. Furthermore, there were no statistically significant correlations between WM microstructure and clinical characteristics.

DISCUSSION

Our findings showed normal WM microstructure in long-term recovered patients, indicating the alterations observed during the acute phase are reversible. Given the paucity of research and inconsistent findings, future studies are warranted to determine the presence of WM microstructure alterations following recovery from AN.

White matter abnormalities in treatment-naive adolescents at the earliest stages of Anorexia Nervosa: A diffusion tensor imaging study

Few studies have examined white matter (WM) integrity in long-lasting Anorexia Nervosa (AN) patients using Diffusion Tensor Imaging (DTI). In this paper, we investigated WM integrity at the earliest stages of AN (i.e. less than 6 months duration). Fourteen treatment-naive female adolescents with AN restrictive type (AN-r) in its earliest stages and 15 age-matched healthy females received brain MRI. Fractional Anisotropy (FA), Axial Diffusivity (AD), Radial diffusivity (RD), and Mean Diffusivity (MD) maps were computed from DTI data using Tract-Based Spatial Statistics analysis. AN-r patients showed FA decreases compared to controls (p_FWE < 0.05) mainly in left anterior and superior corona radiata and left superior longitudinal fasciculus. AN-r patients also showed decreased AD in superior longitudinal fasciculus bilaterally and left superior and anterior corona radiata, (p_FWE < 0.05). No significant differences were found in RD and MD values between the two groups. FA and AD integrity appears to be specifically affected at the earliest stages of AN. Alterations in the microstructural properties of the above mentioned tracts, also involved in cognitive control and visual perception and processing, may be early mechanisms of vulnerability/resilience of WM in AN and sustain the key symptoms of AN, such as impaired cognitive flexibility and body image distortion.

Fornix Under Water? Ventricular Enlargement Biases Forniceal Diffusion Magnetic Resonance Imaging Indices in Anorexia Nervosa

BACKGROUND

Acute anorexia nervosa (AN) is characterized by reduced brain mass and corresponding increased sulcal and ventricular cerebrospinal fluid. Recent studies of white matter using diffusion tensor imaging consistently identified alterations in the fornix, such as reduced fractional anisotropy (FA). However, because the fornix penetrates the ventricles, it is prone to cerebrospinal fluid-induced partial volume effects that interfere with a valid assessment of FA. We investigated the hypothesis that in the acute stage of AN, FA of the fornix is markedly affected by ventricular volumes.

METHODS

First, using diffusion tensor imaging data we established the inverse associations between forniceal FA and volumes of the third and lateral ventricles in a prestudy with 32 healthy subjects to demonstrate the strength of ventricular influence on forniceal FA independent of AN. Second, we investigated a sample of 25 acute AN patients and 25 healthy control subjects.

RESULTS

Using ventricular volumes as covariates markedly reduced the group effect of forniceal FA, even with tract-based spatial statistics focusing only on the center of the fornix. In addition, after correcting for free water on voxel level, the group differences in forniceal FA between AN patients and controls disappeared completely.

CONCLUSIONS

It is unlikely that microstructural changes affecting FA occurred in the fornix of AN patients. Previously identified alterations in acute AN may have been biased by partial volume effects and the proposed central role of this structure in the pathophysiology may need to be reconsidered. Future studies on white matter alterations in AN should carefully deal with partial volume effects.

Limbic-thalamo-cortical projections and reward-related circuitry integrity affects eating behavior: A longitudinal DTI study in adolescents with restrictive eating disorders

Few studies have used diffusion tensor imaging (DTI) to investigate the micro-structural alterations of WM in patients with restrictive eating disorders (rED), and longitudinal data are lacking. Twelve patients with rED were scanned at diagnosis and after one year of family-based treatment, and compared to twenty-four healthy controls (HCs) through DTI analysis. A tract-based spatial statistics procedure was used to investigate diffusivity parameters: fractional anisotropy (FA) and mean, radial and axial diffusivities (MD, RD and AD, respectively). Reduced FA and increased RD were found in patients at baseline in the corpus callosum, corona radiata and posterior thalamic radiation compared with controls. However, no differences were found between follow-up patients and controls, suggesting a partial normalization of the diffusivity parameters. In patients, trends for a negative correlation were found between the baseline FA of the right anterior corona radiata and the Eating Disorder Examination Questionnaire total score, while a positive trend was found between the baseline FA in the splenium of corpus callosum and the weight loss occurred between maximal documented weight and time of admission. A positive trend for correlation was also found between baseline FA in the right anterior corona radiata and the decrease in the Obsessive-Compulsive Inventory Revised total score over time. Our results suggest that the integrity of the limbic–thalamo–cortical projections and the reward-related circuitry are important for cognitive control processes and reward responsiveness in regulating eating behavior.

Altered microstructure of brain white matter in females with anorexia nervosa: a diffusion tensor imaging study

OBJECTIVE

Structural studies have reported anorexia nervosa (AN) patients with abnormal gray matter in several brain regions and dysfunction in some connected neural circuits. However, the role of white matter (WM) in AN patients has rarely been investigated. The present study aimed to assess alterations in WM microstructure of the entire brain in females with AN using a voxel-based method on diffusion tensor imaging (DTI) data.

MATERIALS AND METHODS

The study enrolled 8 female patients with AN and 14 age-matched females as controls (CW). The DTI data was collected from each subject to calculate the fractional anisotropy (FA) maps of the whole brain by the DTI-Studio software. Subsequently, a 2-sample t-test (P<0.05, corrected) was performed to detect the difference in FA maps of AN and CW group, and a Pearson's correlation analyzed the relationship between mean FA value of brain regions and body mass index (BMI).

RESULTS

Compared with CW, AN patients revealed a significant decrease in FA maps in the left superior frontal gyrus, medial frontal gyrus, anterior cingulate cortex, middle frontal gyrus, inferior frontal gyrus, thalamus, and bilateral insula. Moreover, significantly positive correlations were established between the mean FA value of the left inferior frontal gyrus, insula as well as thalamus and BMI in AN patients.

CONCLUSIONS

Our findings supported the presence of WM abnormality in patients with AN. The significant differences of FA maps, in patients with AN, were associated with their aberrant BMI. The results further improved our understanding of the pathophysiological mechanisms underlying AN.

Altered structural and effective connectivity in anorexia and bulimia nervosa in circuits that regulate energy and reward homeostasis

Anorexia and bulimia nervosa are severe eating disorders that share many behaviors. Structural and functional brain circuits could provide biological links that those disorders have in common. We recruited 77 young adult women, 26 healthy controls, 26 women with anorexia and 25 women with bulimia nervosa. Probabilistic tractography was used to map white matter connectivity strength across taste and food intake regulating brain circuits. An independent multisample greedy equivalence search algorithm tested effective connectivity between those regions during sucrose tasting. Anorexia and bulimia nervosa had greater structural connectivity in pathways between insula, orbitofrontal cortex and ventral striatum, but lower connectivity from orbitofrontal cortex and amygdala to the hypothalamus (P<0.05, corrected for comorbidity, medication and multiple comparisons). Functionally, in controls the hypothalamus drove ventral striatal activity, but in anorexia and bulimia nervosa effective connectivity was directed from anterior cingulate via ventral striatum to the hypothalamus. Across all groups, sweetness perception was predicted by connectivity strength in pathways connecting to the middle orbitofrontal cortex. This study provides evidence that white matter structural as well as effective connectivity within the energy-homeostasis and food reward-regulating circuitry is fundamentally different in anorexia and bulimia nervosa compared with that in controls. In eating disorders, anterior cingulate cognitive-emotional top down control could affect food reward and eating drive, override hypothalamic inputs to the ventral striatum and enable prolonged food restriction.

White Matter Integrity Reductions in Intermittent Explosive Disorder

Intermittent explosive disorder (IED), as described in DSM-5, is the categorical expression of pathological impulsive aggression. Previous work has identified neurobiological correlates of the disorder in patterns of frontal-limbic brain activity and dysregulation of serotonergic neurotransmission. Given the importance of short- and-long range white matter connections of the brain in social and emotional behavior, studies of white matter connectivity in impulsive aggression are warranted. Diffusion tensor imaging (DTI) studies in the related conditions of antisocial and borderline personality disorder have produced preliminary evidence of disturbed white matter connectivity in these disorders, but to date there have been no DTI studies in IED. A total of 132 male and female adults between the ages of 18 and 55 years underwent Turboprop-DTI on a 3-Tesla MRI scanner. Of these, 42 subjects had IED, 40 were normal controls, and 50 were clinical psychiatric controls with psychiatric disorders without IED. All subjects were free of alcohol, psychotropic medications, or drugs of abuse. The diffusion tensor was calculated in each voxel and maps of fractional anisotropy (FA) were generated. Tract-based spatial statistics (TBSS) were used to compare FA along the white matter skeleton among the three subject groups. IED was associated with lower FA in two clusters located in the superior longitudinal fasciculus (SLF) when compared with the psychiatric and healthy controls. Impulsive aggression and borderline personality disorder, but not psychopathy or antisocial personality disorder, was associated with lower FA in the two clusters within the SLF. In conclusion, IED was associated with lower white matter integrity in long-range connections between the frontal and temporoparietal regions.

Mammillary body volume abnormalities in anorexia nervosa

OBJECTIVE

Several case reports of Wernicke's Encephalopathy in anorexia nervosa (AN) caused by thiamine deficiency have described mammillary body (MB) injury, but systematic studies are lacking. Here we evaluated whether underweight and weight-restored individuals with AN demonstrate evidence of abnormal MB morphology, via retrospective examination of a previously collected data set.

METHOD

Using standard-resolution T1-weighted magnetic resonance imaging at 3 Tesla, we measured MB volume and fornix area in a cross-sectional study of 12 underweight AN, 20 weight-restored AN, and 30 age- and sex-matched healthy comparisons. Because of the small size of these structures, a manual tracing approach was necessary to obtain accurate measurements. A blinded expert rater manually traced MB and fornix structures in each participant.

RESULTS

We observed significantly smaller MB volumes in the underweight AN group. However, the weight-restored AN group exhibited significantly larger MB volumes. The right fornix was smaller in the weight-restored AN group only.

DISCUSSION

These findings suggest the possibility that MB volume and fornix area could represent potential biomarkers of acute weight loss and restoration, respectively. Verification of this finding through prospective studies evaluating MB morphology, cognition, and thiamine levels longitudinally across individual illness trajectories might be warranted. © 2016 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:920-929).

Altered White Matter Microstructure in Adolescents and Adults with Bulimia Nervosa

Previous data suggest structural and functional deficits in frontal control circuits in adolescents and adults with bulimia nervosa (BN), but less is known about the microstructure of white matter in these circuits early in the course of the disorder. Diffusion tensor imaging (DTI) data were acquired from 28 female adolescents and adults with BN and 28 age- and BMI-matched healthy female participants. Tract-based spatial statistics (TBSS) was used to detect group differences in white matter microstructure and explore the differential effects of age on white matter microstructure across groups. Significant reductions in fractional anisotropy (FA) were detected in the BN compared with healthy control group in multiple tracts including forceps minor and major, superior longitudinal, inferior fronto-occipital, and uncinate fasciculi, anterior thalamic radiation, cingulum, and corticospinal tract. FA reductions in forceps and frontotemporal tracts correlated inversely with symptom severity and Stroop interference in the BN group. These findings suggest that white matter microstructure is abnormal in BN in tracts extending through frontal and temporoparietal cortices, especially in those with the most severe symptoms. Age-related differences in both FA and RD in these tracts in BN compared with healthy individuals may represent an abnormal trajectory of white matter development that contributes to the persistence of functional impairments in self-regulation in BN.

White matter microstructural changes in adolescent anorexia nervosa including an exploratory longitudinal study

BACKGROUND

Anorexia nervosa (AN) often begins in adolescence, however, the understanding of the underlying pathophysiology at this developmentally important age is scarce, impeding early interventions. We used diffusion tensor imaging (DTI) to investigate microstructural white matter (WM) brain changes including an experimental longitudinal follow-up.

METHODS

We acquired whole brain diffusion-weighted brain scans of 22 adolescent female hospitalized patients with AN at admission and nine patients longitudinally at discharge after weight rehabilitation. Patients (10-18 years) were compared to 21 typically developing controls (TD). Tract-based spatial statistics (TBSS) were applied to compare fractional anisotropy (FA) across groups and time points. Associations between average FA values of the global WM skeleton and weight as well as illness duration parameters were analyzed by multiple linear regression.

RESULTS

We observed increased FA in bilateral frontal, parietal and temporal areas in AN patients at admission compared to TD. Higher FA of the global WM skeleton at admission was associated with faster weight loss prior to admission. Exploratory longitudinal analysis showed this FA increase to be partially normalized after weight rehabilitation.

CONCLUSIONS

Our findings reveal a markedly different pattern of WM microstructural changes in adolescent AN compared to most previous results in adult AN. This could signify a different susceptibility and reaction to semi-starvation in the still developing brain of adolescents or a time-dependent pathomechanism differing with extend of chronicity. Higher FA at admission in adolescents with AN could point to WM fibers being packed together more closely.

White matter alterations in anorexia nervosa: A systematic review of diffusion tensor imaging studies

AIM

To identify findings concerning white matter (WM) fibre microstructural alterations in anorexia nervosa (AN).

METHODS

A systematic electronic search was undertaken in several databases up to April 2015. The search strategy aimed to locate all studies published in English or Spanish that included participants with AN and which investigated WM using diffusion tensor imaging (DTI). Trials were assessed for quality assessment according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses checklist and a published quality index guideline.

RESULTS

A total of 6 studies met the inclusion criteria, four of people in the acute state of the illness, one included both recovered and unwell participants, and one included people who had recovered. Participants were female with ages ranging from 14 to 29 years. All studies but one measured a range of psychopathological features. Fractional anisotropy and mean diffusivity were the main DTI correlates reported. Alterations were reported in a range of WM structures of the limbic system, most often of the fornix and cingulum as well as the fronto-occipital fibre tracts, i.e., regions associated with anxiety, body image and cognitive function. Subtle abnormalities also appeared to persist after recovery.

CONCLUSION

This diversity likely reflects the symptom complexity of AN. However, there were few studies, they applied different methodologies, and all were cross-sectional.

Weight restoration therapy rapidly reverses cortical thinning in anorexia nervosa: A longitudinal study

Structural magnetic resonance imaging studies have documented reduced gray matter in acutely ill patients with anorexia nervosa to be at least partially reversible following weight restoration. However, few longitudinal studies exist and the underlying mechanisms of these structural changes are elusive. In particular, the relative speed and completeness of brain structure normalization during realimentation remain unknown. Here we report from a structural neuroimaging study including a sample of adolescent/young adult female patients with acute anorexia nervosa (n=47), long-term recovered patients (n=34), and healthy controls (n=75). The majority of acutely ill patients were scanned longitudinally (n=35): at the beginning of standardized weight restoration therapy and again after partial weight normalization (>10% body mass index increase). High-resolution structural images were processed and analyzed with the longitudinal stream of FreeSurfer software to test for changes in cortical thickness and volumes of select subcortical regions of interest. We found globally reduced cortical thickness in acutely ill patients to increase rapidly (0.06 mm/month) during brief weight restoration therapy (≈3 months). This significant increase was predicted by weight restoration alone and could not be ascribed to potentially mediating factors such as duration of illness, hydration status, or symptom improvements. By comparing cortical thickness in partially weight-restored patients with that measured in healthy controls, we confirmed that cortical thickness had normalized already at follow-up. This pattern of thinning in illness and rapid normalization during weight rehabilitation was largely mirrored in subcortical volumes. Together, our findings indicate that structural brain insults inflicted by starvation in anorexia nervosa may be reversed at a rate much faster than previously thought if interventions are successful before the disorder becomes chronic. This provides evidence drawing previously speculated mechanisms such as (de-)hydration and neurogenesis into question and suggests that neuronal and/or glial remodeling including changes in macromolecular content may underlie the gray matter alterations observed in anorexia nervosa.

Greater Insula White Matter Fiber Connectivity in Women Recovered from Anorexia Nervosa

Anorexia nervosa is a severe psychiatric disorder associated with reduced drive to eat. Altered taste-reward circuit white matter fiber organization in anorexia nervosa after recovery could indicate a biological marker that alters the normal motivation to eat. Women recovered from restricting-type anorexia (Recovered AN, n = 24, age = 30.3 ± 8.1 years) and healthy controls (n = 24, age = 27.4 ± 6.3 years) underwent diffusion weighted imaging of the brain. Probabilistic tractography analyses calculated brain white matter connectivity (streamlines) as an estimate of fiber connections in taste-reward-related white matter tracts, and microstructural integrity (fractional anisotropy, FA) was assessed using tract-based spatial statistics. Recovered AN showed significantly (range P<0.05-0.001, Bonferroni corrected) greater white matter connectivity between bilateral insula regions and ventral striatum, left insula and middle orbitofrontal cortex (OFC), and right insula projecting to gyrus rectus and medial OFC. Duration of illness predicted connectivity of tracts projecting from the insula to ventral striatum and OFC. Microstructural integrity was lower in Recovered AN in most insula white matter tracts, as was whole-brain FA in parts of the anterior corona radiata, external capsule, and cerebellum (P<0.05, family-wise error-corrected). This study indicates higher structural white matter connectivity, an estimate of fibers connections, in anorexia after recovery in tracts that connect taste-reward processing regions. Greater connectivity together with less-fiber integrity could indicate altered neural activity between those regions, which could interfere with normal food-reward circuit function. Correlations between connectivity and illness duration suggest that connectivity could be a marker for illness severity. Whether greater connectivity can predict prognosis of the disorder requires further study.

Anorexia nervosa

Anorexia nervosa (AN) is a psychiatric condition characterized by severe weight loss and secondary problems associated with malnutrition. AN predominantly develops in adolescence in the peripubertal period. Without early effective treatment, the course is protracted with physical, psychological and social morbidity and high mortality. Despite these effects, patients are noted to value the beliefs and behaviours that contribute to their illness rather than regarding them as problematic, which interferes with screening, prevention and early intervention. Involving the family to support interventions early in the course of the illness can produce sustained changes; however, those with a severe and/or protracted illness might require inpatient nursing support and/or outpatient psychotherapy. Prevention programmes aim to moderate the overvaluation of 'thinness' and body dissatisfaction as one of the proximal risk factors. The low prevalence of AN limits the ability to identify risk factors and to study the timing and sex distribution of the condition. However, genetic profiles, premorbid features, and brain structures and functions of patients with AN show similarities with other psychiatric disorders and contrast with obesity and metabolic disorders. Such studies are informing approaches to address the neuroadaptation to starvation and the other various physical and psychosocial deficits associated with AN. This Primer describes the epidemiology, diagnosis, screening and prevention, aetiology, treatment and quality of life of patients with AN.

Abnormal white matter properties in adolescent girls with anorexia nervosa

Anorexia nervosa (AN) is a serious eating disorder that typically emerges during adolescence and occurs most frequently in females. To date, very few studies have investigated the possible impact of AN on white matter tissue properties during adolescence, when white matter is still developing. The present study evaluated white matter tissue properties in adolescent girls with AN using diffusion MRI with tractography and T1 relaxometry to measure R1 (1/T1), an index of myelin content. Fifteen adolescent girls with AN (mean age = 16.6 years ± 1.4) were compared to fifteen age-matched girls with normal weight and eating behaviors (mean age = 17.1 years ± 1.3). We identified and segmented 9 bilateral cerebral tracts (18) and 8 callosal fiber tracts in each participant's brain (26 total). Tract profiles were generated by computing measures for fractional anisotropy (FA) and R1 along the trajectory of each tract. Compared to controls, FA in the AN group was significantly decreased in 4 of 26 white matter tracts and significantly increased in 2 of 26 white matter tracts. R1 was significantly decreased in the AN group compared to controls in 11 of 26 white matter tracts. Reduced FA in combination with reduced R1 suggests that the observed white matter differences in AN are likely due to reductions in myelin content. For the majority of tracts, group differences in FA and R1 did not occur within the same tract. The present findings have important implications for understanding the neurobiological factors underlying white matter changes associated with AN and invite further investigations examining associations between white matter properties and specific physiological, cognitive, social, or emotional functions affected in AN.

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AN girls had both increased and decreased FA in 4 white matter tracts.

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AN girls had increased R1 in 11 white matter tracts.

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White matter differences in AN are likely related to changes in myelin content.