Processing of Food, Body and Emotional Stimuli in Anorexia Nervosa: A Systematic Review and Meta-analysis of Functional Magnetic Resonance Imaging Studies

The Role of Essential Fatty Acids in Anorexia Nervosa and Obesity

The two basic questions in food intake study are what we eat, and how much do we eat. Most research is directed toward the control of how much is eaten. This is likely the result of the increased number of individuals with eating disorders in the Western world. Feeding behavior is highly complex, and is controlled by many psychological, physiological, biochemical, and immunological factors. The aim of this review is to clarify the involvement of fatty acids in eating disorders such as anorexia and binge eating disorder. The review will describe the modified fatty acid profile observed in individuals with anorexia or binge eating disorder, and discuss on what factors fatty acids can exert beneficial effects. In addition, the differences and similarities between anorexia and binge eating disorder will be discussed. We suggest that beneficial effects of essential fatty acids on both anorexia and binge eating disorder can be explained by the stabilizing effect of those fatty acids on the neuronal membrane fluidity index.

Automatic processing of emotional stimuli in euthymic patients with bipolar disorder

BACKGROUND

Biased information processing styles are a core feature of cognitive models of unipolar depression (UD). The manic-defence hypothesis (MDH) posits that UD and Bipolar Disorder (BD) are subject partially to the same underlying cognitive processes, which may act as putative vulnerability factors. Previous studies have used experimental paradigms as a way of measuring automatic (non-intentional) processing of emotional information in order to test the MDH with some studies providing some evidence for a negatively biased automatic processing of emotionally-relevant information in BD. However, most prior studies used supraliminal stimuli (i.e. presented above perceptual threshold). Based on the MDH we predicted that subliminally presented negative stimuli will affect performance of patients with BD differently than non-clinical participants, but similarly to what has been observed in prior studies with currently depressed patients.

METHODS

The current study used an affective priming paradigm with both supraliminally and subliminally presented emotional images as primes to measure automatic processing. Seventeen euthymic individuals with a BD diagnosis were recruited along with seventeen non-clinical control participants (NCC) matched for age and gender.

RESULTS

We found interference (increased response times) due to masked, subliminally presented negative primes in patients with BD when negative prime images were followed by negative targets, but decreased response times (facilitation) in NCCs.

LIMITATIONS

We did not include a psychiatric control group and the sample size was small.

CONCLUSION

Our findings suggest that euthymic patients with BD do exhibit an affective bias suggesting an increased sensitivity to negative emotional information even when euthymic.

Higher Adolescent Body Mass Index Is Associated with Lower Regional Gray and White Matter Volumes and Lower Levels of Positive Emotionality

Adolescent obesity is associated with an increased chance of developing serious health risks later in life. Identifying the neurobiological and personality factors related to increases in adiposity is important to understanding what drives maladaptive consummatory and exercise behaviors that result in obesity. Previous research has largely focused on adults with few findings published on interactions among adiposity, brain structure, and personality. In this study, Voxel Based Morphometry (VBM) was used to identify associations between gray and white matter volumes and increasing adiposity, as measured by Body Mass Index percentile (BMI%), in 137 adolescents (age range: 9–20 years, BMI% range: 5.16–99.56). Variations in gray and white matter volume and BMI% were then linked to individual differences in personality measures from the Multidimensional Personality Questionnaire (MPQ). After controlling for age and other covariates, BMI% correlated negatively with gray matter volume in the bilateral caudate (right: partial r = −0.338, left: r = −0.404), medial prefrontal cortex (partial r = −0.339), anterior cingulate (partial r = −0.312), bilateral frontal pole (right: partial r = −0.368, left: r = −0.316), and uncus (partial r = −0.475) as well as white matter volume bilaterally in the anterior limb of the internal capsule (right: partial r = −0.34, left: r = −0.386), extending to the left middle frontal subgyral white matter. Agentic Positive Emotionality (PEM-AG) was correlated negatively with BMI% (partial r = −0.384). PEM-AG was correlated positively with gray matter volume in the right uncus (partial r = 0.329). These results suggest that higher levels of adiposity in adolescents are associated with lower trait levels in reward-related personality domains, as well as structural variations in brain regions associated with reward processing, control, and sensory integration.

Alterations in emotion generation and regulation neurocircuitry in depression and eating disorders: A comparative review of structural and functional neuroimaging studies

Major depression and eating disorders (EDs) are highly co-morbid and may share liability. Impaired emotion regulation may represent a common etiological or maintaining mechanism. Research has demonstrated that depressed individuals and individuals with EDs exhibit impaired emotion regulation, with these impairments being associated with changes in brain structure and function. The goal of this review was to evaluate findings from neuroimaging studies of depression and EDs to determine whether there are overlapping alterations in the brain regions known to be involved in emotion regulation, evidence of which would aid in the diagnosis and treatment of these conditions. Our review of the literature suggests that depression and EDs exhibit common structural and functional alterations in brain regions involved in emotion regulation, including the amygdala, ventral striatum and nucleus accumbens, anterior cingulate cortex, insula, and dorsolateral prefrontal cortex. We present preliminary support for a shared etiological mechanism. Future studies should consider manipulating emotion regulation in a sample of individuals with depression and EDs to better characterize abnormalities in these brain circuits.

Increased anticipatory but decreased consummatory brain responses to food in sisters of anorexia nervosa patients

BACKGROUND

We have previously shown increased anticipatory and consummatory neural responses to rewarding and aversive food stimuli in women recovered from anorexia nervosa (AN).

AIMS

To determine whether these differences are trait markers for AN, we examined the neural response in those with a familial history but no personal history of AN.

METHOD

Thirty-six volunteers were recruited: 15 who had a sister with anorexia nervosa (family history) and 21 control participants. Using fMRI we examined the neural response during an anticipatory phase (food cues, rewarding and aversive), an effort phase and a consummatory phase (rewarding and aversive tastes).

RESULTS

Family history (FH) volunteers showed increased activity in the caudate during the anticipation of both reward and aversive food and in the thalamus and amygdala during anticipation of aversive only. FH had decreased activity in the dorsal anterior cingulate cortex, the pallidum and the superior frontal gyrus during taste consumption.

CONCLUSIONS

Increased neural anticipatory but decreased consummatory responses to food might be a biomarker for AN. Interventions that could normalise these differences may help to prevent disorder onset.

DECLARATION OF INTEREST

C.M. has acted as a consultant to P1VITAL, Givaudan, GWPharma, the British Broadcasting Corporation (BBC) and Channel 4.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license.

EEG neurofeedback effects in the treatment of adolescent anorexia nervosa

A pre-post design including 22 females was used to evaluate the effectiveness of neurofeedback in the treatment of adolescent anorexia nervosa. Resting EEG measures and a psychological test-battery assessing eating behavior traits, clinical symptoms, emotionality, and mood were obtained. While both the experimental (n = 10) and control group (n = 12) received their usual maintenance treatment, the experimental group received 10 sessions of individual alpha frequency training over a period of 5 weeks as additional treatment. Significant training effects were shown in eating behavior traits, emotion regulation, and in relative theta power in the eyes closed condition. Although the results are limited due to the small sample size, these are the first empirical data demonstrating the benefits of neurofeedback as a treatment adjunct in individuals with anorexia nervosa.

New Insights in Anorexia Nervosa

Anorexia nervosa (AN) is classically defined as a condition in which an abnormally low body weight is associated with an intense fear of gaining weight and distorted cognitions regarding weight, shape, and drive for thinness. This article reviews recent evidences from physiology, genetics, epigenetics, and brain imaging which allow to consider AN as an abnormality of reward pathways or an attempt to preserve mental homeostasis. Special emphasis is put on ghrelino-resistance and the importance of orexigenic peptides of the lateral hypothalamus, the gut microbiota and a dysimmune disorder of neuropeptide signaling. Physiological processes, secondary to underlying, and premorbid vulnerability factors-the "pondero-nutritional-feeding basements"- are also discussed.

Voluntary emotion regulation in anorexia nervosa: A preliminary emotion-modulated startle investigation

Emotion regulation difficulties are implicated in the development and maintenance of anorexia nervosa (AN). However, research has been limited by an almost exclusive reliance on self-report. This study is the first to use the emotion-modulated startle paradigm (EMSP) to investigate emotional reactivity and voluntary emotion regulation in individuals with AN. Twenty women with AN viewed negative, positive, neutral, and food images and were asked to enhance, suppress, or maintain their emotional responses mid-way through picture presentation. Startle eyeblink magnitudes in response to startle probes administered prior, and subsequent, to regulation instructions indexed emotional reactivity and regulation, respectively. On emotional reactivity trials, startle magnitudes were greater for negative, positive, and food images, compared to neutral images. Participants had difficulty suppressing startle responses to negative and food images, as indicated by non-significant suppress-maintain comparisons. In contrast, startle responses to enhance and suppress cues during presentation of pleasant images were comparable and significantly lower than maintain cues. Findings converge with self-report data to suggest that patients with AN have difficulties with voluntary emotion regulation. The EMSP may be a promising trans-diagnostic method for examining emotion regulation difficulties that underlie risk for eating disorders and other psychiatric conditions.

Two cases of food aversion with semantic dementia

Accounts of altered eating behavior in semantic dementia generally emphasize gluttony and abnormal food preferences. Here we describe two female patients with no past history of eating disorders who developed early prominent aversion to food in the context of an otherwise typical semantic dementia syndrome. One patient (aged 57) presented features in line with anorexia nervosa while the second patient (aged 58) presented with a syndrome more suggestive of bulimia nervosa. These cases add to the growing spectrum of apparently dichotomous behavior patterns in the frontotemporal dementias and illustrate a potentially under-recognized cause of eating disorders presenting in later life.

A core eating network and its modulations underlie diverse eating phenomena

We propose that a core eating network and its modulations account for much of what is currently known about the neural activity underlying a wide range of eating phenomena in humans (excluding homeostasis and related phenomena). The core eating network is closely adapted from a network that Kaye, Fudge, and Paulus (2009) proposed to explain the neurocircuitry of eating, including a ventral reward pathway and a dorsal control pathway. In a review across multiple literatures that focuses on experiments using functional Magnetic Resonance Imaging (fMRI), we first show that neural responses to food cues, such as food pictures, utilize the same core eating network as eating. Consistent with the theoretical perspective of grounded cognition, food cues activate eating simulations that produce reward predictions about a perceived food and potentially motivate its consumption. Reviewing additional literatures, we then illustrate how various factors modulate the core eating network, increasing and/or decreasing activity in subsets of its neural areas. These modulating factors include food significance (palatability, hunger), body mass index (BMI, overweight/obesity), eating disorders (anorexia nervosa, bulimia nervosa, binge eating), and various eating goals (losing weight, hedonic pleasure, healthy living). By viewing all these phenomena as modulating a core eating network, it becomes possible to understand how they are related to one another within this common theoretical framework. Finally, we discuss future directions for better establishing the core eating network, its modulations, and their implications for behavior.

A Randomised Controlled Trial of Neuronavigated Repetitive Transcranial Magnetic Stimulation (rTMS) in Anorexia Nervosa

Background

Anorexia nervosa (AN) is associated with morbid fear of fatness, extreme food restriction and altered self-regulation. Neuroimaging data implicate fronto-striatal circuitry, including the dorsolateral prefrontal cortex (DLPFC).

Methods

In this double-blind parallel group study, we investigated the effects of one session of sham-controlled high-frequency repetitive transcranial magnetic stimulation (rTMS) to the left DLPFC (l-DLPFC) in 60 individuals with AN. A food exposure task was administered before and after the procedure to elicit AN-related symptoms.

Outcomes

The primary outcome measure was ‘core AN symptoms’, a variable which combined several subjective AN-related experiences. The effects of rTMS on other measures of psychopathology (e.g. mood), temporal discounting (TD; intertemporal choice behaviour) and on salivary cortisol concentrations were also investigated. Safety, tolerability and acceptability were assessed.

Results

Fourty-nine participants completed the study. Whilst there were no interaction effects of rTMS on core AN symptoms, there was a trend for group differences (p = 0.056): after controlling for pre-rTMS scores, individuals who received real rTMS had reduced symptoms post-rTMS and at 24-hour follow-up, relative to those who received sham stimulation. Other psychopathology was not altered differentially following real/sham rTMS. In relation to TD, there was an interaction trend (p = 0.060): real versus sham rTMS resulted in reduced rates of TD (more reflective choice behaviour). Salivary cortisol concentrations were unchanged by stimulation. rTMS was safe, well–tolerated and was considered an acceptable intervention.

Conclusions

This study provides modest evidence that rTMS to the l-DLPFC transiently reduces core symptoms of AN and encourages prudent decision making. Importantly, individuals with AN considered rTMS to be a viable treatment option. These findings require replication in multiple-session studies to evaluate therapeutic efficacy.

Trial Registration

www.Controlled-Trials.comISRCTN22851337

Amygdala alterations during an emotional conflict task in women recovered from anorexia nervosa

The pathophysiology of anorexia nervosa (AN) is not completely understood, but research suggests that alterations in brain circuits related to cognitive control and emotion are central. The aim of this study was to explore neural responses to an emotional conflict task in women recovered from AN. Functional magnetic resonance imaging was used to measure neural responses to an emotional conflict task in 22 women recovered from AN and 21 age-matched healthy controls. The task involved categorizing affective faces while ignoring affective words. Face and word stimuli were either congruent (non-conflict) or incongruent (conflict). Brain responses to emotional conflict did not differ between groups. However, in response to emotional non-conflict, women recovered from AN relative to healthy controls showed significantly less activation in the bilateral amygdala. Specifically, while emotional non-conflict evoked significant activations of the amygdala in healthy controls, recovered AN women did not show such activations. Similar significant group differences were also observed in the hippocampus and basal ganglia. These results suggest that women recovered from AN are characterized by alterations within emotion-related brain circuits. Recovered women's absence of amygdala and hippocampus activation during non-conflict trials possibly reflects an impaired ability to process emotional significant stimuli.

Functional brain alterations in anorexia nervosa: a scoping review

BACKGROUND

Neuroimaging allows for the identification of brain abnormalities and alterations that are associated with anorexia nervosa (AN). We performed a scoping review to map out the extent and nature of recent research activity on functional magnetic resonance imaging (fMRI) in individuals diagnosed with, or recovered from, AN (AN-REC).

MAIN TEXT

A literature search of PubMed, Psychinfo and Embase was conducted using the search terms "anorexia nervosa" AND "functional magnetic resonance imaging." We included fMRI studies that involved a comparison between individuals with AN or AN-REC and healthy controls published in English language between 2010 and 2015. A total of 49 papers were included, regardless of the experimental stimuli or paradigm.

CONCLUSIONS

Findings varied considerably across studies, reflecting methodological differences in study design, such as sample differences and experimental paradigms. Collectively, studies published during the past five years suggest altered activation in regions related to the fronto-striato and the limbic circuits, which are theorized to have an important role in the pathophysiology of AN.

Reward-related decision making in eating and weight disorders: A systematic review and meta-analysis of the evidence from neuropsychological studies

Eating disorders (EDs) and overweight/obesity (OW/OB) are serious public health concerns that share common neuropsychological features and patterns of disturbed eating. Reward-related decision making as a basic neurocognitive function may trans-diagnostically underlie both pathological overeating and restricted eating. The present meta-analysis synthesizes the evidence from N=82 neuropsychological studies for altered reward-related decision making in all ED subtypes, OW and OB. The overall effect sizes for the differences between currently-ill ED patients and OW/OB people and controls were Hedge's g=-0.49 [CI: -0.63; -0.35], and Hedge's g=-0.39 [CI: -0.53; -0.25], respectively. Decision making was found to be altered to similar degrees in all ED subtypes and OB. Effect sizes, however, diverged for the different measures of decision making. Adolescents appear to be less affected than adults. When foods were used as rewarding stimuli, decision making was found to be intact in OB. The findings support that altered general reward-related decision making is a salient neuropsychological factor across eating and weight disorders in adulthood.

Clinical outcomes and neural correlates of 20 sessions of repetitive transcranial magnetic stimulation in severe and enduring anorexia nervosa (the TIARA study): study protocol for a randomised controlled feasibility trial

BACKGROUND

Anorexia nervosa (AN) is a serious mental disorder with multiple comorbidities and complications. In those with a severe and enduring form of the illness (SEED-AN), treatment responsivity is poor and the evidence base limited. Thus, there is a need for novel treatment strategies. This paper describes the theoretical background and protocol of a feasibility randomised controlled trial (RCT) of real versus sham (placebo) therapeutic repetitive transcranial magnetic stimulation (rTMS) in SEED-AN. The aim of this trial is to obtain information that will guide decision making and protocol development in relation to a future large-scale RCT of rTMS in this group of patients, and also to assess the preliminary efficacy and neural correlates of rTMS treatment.

DESIGN

Forty-four adults from the community with a DSM-5 diagnosis of AN, an illness duration>3 years and a previous course of unsuccessful treatment will be randomly allocated to receive 20 sessions of either real or sham rTMS, in a parallel group design. As this is a feasibility study, no primary outcome has been defined and a broad range of outcome variables will be examined. These include weight/body mass index (BMI), eating disorder psychopathology, other psychopathology (for example, depression, anxiety), quality of life, neuropsychological processes (such as self-regulation, attentional bias and food choice behaviour), neuroimaging measures (that is, changes in brain structure or function), tolerability and acceptability of rTMS, and additional service utilisation. The feasibility of conducting a large-scale RCT of rTMS and the appropriateness of rTMS as a treatment for SEED-AN will be evaluated through: assessment of recruitment and retention rates, acceptability of random allocation, blinding success (allocation concealment), completion of treatment sessions and research assessments (baseline, post-treatment and follow-up assessments). The acceptability and tolerability of the treatment will be assessed via semi-structured interviews.

DISCUSSION

The effect sizes generated and other findings from this trial will inform a future large-scale RCT with respect to decisions on primary outcome measures and other aspects of protocol development. Additionally, results from this study will provide a preliminary indication of the efficacy of rTMS treatment for AN, the neural correlates of the illness, and potential biomarkers of clinical response.

TRIAL REGISTRATION

ISRCTN14329415 . Date of registration: 23 July 2015.

Anorexia nervosa: aetiology, assessment, and treatment

Anorexia nervosa is an important cause of physical and psychosocial morbidity. Recent years have brought advances in understanding of the underlying psychobiology that contributes to illness onset and maintenance. Genetic factors influence risk, psychosocial and interpersonal factors can trigger onset, and changes in neural networks can sustain the illness. Substantial advances in treatment, particularly for adolescent patients with anorexia nervosa, point to the benefits of specialised family-based interventions. Adults with anorexia nervosa too have a realistic chance of achieving recovery or at least substantial improvement, but no specific approach has shown clear superiority, suggesting a combination of re-nourishment and anorexia nervosa-specific psychotherapy is most effective. To successfully fight this enigmatic illness, we have to enhance understanding of the underlying biological and psychosocial mechanisms, improve strategies for prevention and early intervention, and better target our treatments through improved understanding of specific disease mechanisms.

Altered orienting of attention in anorexia nervosa

The study of cognitive processes in anorexia nervosa (AN) is largely unexplored, although recent evidence suggests the presence of impairments in both social cognition and attention processing. Here we investigated AN patients' ability to orient attention in response to social and symbolic visual stimuli. AN patients and matched controls performed a task in which gaze and pointing gestures acted as social directional cues for spatial attention. Arrows were also included as symbolic cue. On each trial, a centrally-placed cue appeared oriented rightwards or leftwards. After either 200 or 700ms, a lateralized neutral target (a letter) requiring a discrimination response appeared in a location either spatially congruent or incongruent with the directional cue. Controls showed a reliable orienting irrespective of both temporal interval and cue type. AN patients showed a reliable orienting at both temporal intervals only in response to pointing gestures. Both gaze and arrow cues failed to orient attention at the short temporal interval, that is when attention is under reflexive control, whereas a reliable orienting emerged at the long temporal interval. These results provide preliminary evidence of altered reflexive orienting of attention in AN patients that does not extend to body-related cues such as pointing gestures.

Neural correlates of eating disorders: translational potential

Eating disorders are complex and serious psychiatric illnesses whose etiology includes psychological, biological, and social factors. Treatment of eating disorders is challenging as there are few evidence-based treatments and limited understanding of the mechanisms that result in sustained recovery. In the last 20 years, we have begun to identify neural pathways that are altered in eating disorders. Consideration of how these pathways may contribute to an eating disorder can provide an understanding of expected responses to treatments. Eating disorder behaviors include restrictive eating, compulsive overeating, and purging behaviors after eating. Eating disorders are associated with changes in many neural systems. In this targeted review, we focus on three cognitive processes associated with neurocircuitry differences in subjects with eating disorders such as reward, decision-making, and social behavior. We briefly examine how each of these systems function in healthy people, using Neurosynth meta-analysis to identify key regions commonly implicated in these circuits. We review the evidence for disruptions of these regions and systems in eating disorders. Finally, we describe psychiatric and psychological treatments that are likely to function by impacting these regions.

Characteristics of Disorder-Related Autobiographical Memory in Acute Anorexia Nervosa Patients

OBJECTIVE

First studies revealed overgeneral autobiographical memories in anorexia nervosa (AN) patients. The aim of the present study was to investigate frequency, generalization and valence of autobiographical memories in AN patients in response to eating disorder-related cue words.

METHOD

Autobiographical memory was examined in 21 AN patients and 21 healthy controls (HC) using a modified version of the Autobiographical Memory Test, incorporating body-related, food-related, perfectionism-related, depression-related and neutral cues.

RESULTS

Anorexia nervosa patients recalled fewer and more general autobiographical memories compared with HC. For eating disorder-related cues as against neutral ones, AN patients compared with HC showed fewer memories for food-related and body-related cues, an elevated overgeneralization for food-related cues, while the valence of the retrieved memories was more negative in response to body-related cues.

DISCUSSION

This study detects disorder-related autobiographical memory alterations in AN, which are intensified in response to symptom-related cues. The findings are discussed with regard to their maladaptive function in emotion regulation.

Altered food-cue processing in chronically ill and recovered women with anorexia nervosa

Anorexia nervosa (AN) is a severe mental disorder characterized by food restriction and weight loss. This study aimed to test the model posed by Brooks et al. (2012a,b) that women suffering from chronic AN show decreased food-cue processing activity in brain regions associated with energy balance and food reward (bottom-up; BU) and increased activity in brain regions associated with cognitive control (top-down; TD) when compared with long-term recovered AN (REC) and healthy controls (HC). Three groups of women, 15 AN (mean illness duration 7.8 ± 4.1 years), 14 REC (mean duration of recovery 4.7 ± 2.7 years) and 15 HC viewed alternating blocks of food and non-food images preceded by a short instruction during functional magnetic resonance imaging (fMRI), after fasting overnight. Functional region of interests (fROIs) were defined in BU (e.g., striatum, hippocampus, amygdala, hypothalamus, and cerebellum), TD (e.g., medial and lateral prefrontal cortex, and anterior cingulate), the insula, and visual processing areas (VPA). Food-cue processing activation was extracted from all fROIs and compared between the groups. In addition, functional connectivity between the fROIs was examined by modular partitioning of the correlation matrix of all fROIs. We could not confirm the hypothesis that BU areas are activated to a lesser extent in AN upon visual processing of food images. Among the BU areas the caudate showed higher activation in both patient groups compared to HC. In accordance with Brooks et al.'s model, we did find evidence for increased TD control in AN and REC. The functional connectivity analysis yielded two clusters in HC and REC, but three clusters in AN. In HC, fROIs across BU, TD, and VPA areas clustered; in AN, one cluster span across BU, TD, and insula; one across BU, TD, and VPA areas; and one was confined to the VPA network. In REC, BU, TD, and VPA or VPA and insula clustered. In conclusion, despite weight recovery, neural processing of food cues is also altered in recovered AN patients.

Alterations in Activity, Volume, and Connectivity of Body-Processing Brain Areas in Anorexia Nervosa

Body image disturbance is one of the main symptoms of eating disorders; however, the neural basis of this phenomenon is not well understood yet. In the present paper, we review studies investigating the neuronal correlates of visual body perception in anorexia nervosa. We first focus on the well-known parietal lobe contribution to body image processing and its malfunction. Additionally, we focus on the contribution and involvement of the extrastriate and fusiform body area in eating disorders, especially anorexia nervosa. The summarized studies provide first evidence for a reduced activity, volume, and connectivity in brain areas involved and specialized in the visual processing of human bodies. In general, the reviewed studies provide evidence for abnormalities in body-processing brain areas in anorexia nervosa, indicating two structures in the brain that are involved: early stages of body processing in the visual extrastriate cortex and later stages in the parietal cortex.

Attentional biases to body shape images in adolescents with anorexia nervosa: an exploratory eye-tracking study

Body image distortion (BID) plays an important role in the etiology and maintenance of anorexia nervosa (AN). Previous studies of BID in AN showed small biases in visual scanning behavior (VSB) towards images of body shapes. The aim of this study is to investigate biases in VSB when body shape images compete with images with a different theme (social interactions) for subjects׳ attention. When images of thin body shapes (TBS) were presented alongside images of social interactions, AN patients (n=13) spent significantly more time looking at TBSs rather than at social interactions, but controls (n=20) did not. When images of fat body shapes (FBS) were presented alongside images of social interactions, AN patients spent significantly more time looking at FBSs rather than at social interactions, but controls did not. When images of TBSs, FBSs and social interactions were presented alongside each other, AN patients demonstrated a hierarchy in their attention allocation, choosing to spend the most viewing time on TBS images, followed by FBS images and then images with social interactions. Under the three experimental conditions, AN patients demonstrated large biases in their visual scanning behavior (VSB). Biases in VSB may provide physiologically objective measures that characterize patients with AN.

Alterations in brain structure in adults with anorexia nervosa and the impact of illness duration

BACKGROUND

Brain structure alterations have been reported in anorexia nervosa, but findings have been inconsistent. This may be due to inadequate sample size, sample heterogeneity or differences in methodology.

METHOD

High resolution magnetic resonance images were acquired of 33 adult participants with anorexia nervosa and 33 healthy participants, the largest study sample to date, in order to assess whole-brain volume, ventricular cerebrospinal fluid, white matter and grey matter volume. Voxel-based morphometry was conducted to assess regional grey matter volume. Levels of depression, anxiety, obsessionality and eating disorder-related symptoms were measured and used to explore correlations with brain structure.

RESULTS

Participants with anorexia nervosa had smaller brain volumes as well as a global decrease in grey matter volume with ventricular enlargement. Voxel-based morphometry revealed a decrease in grey matter volume spanning across the cerebellum, temporal, frontal and occipital lobes. A correlation was found between grey matter volume loss and duration of illness in the cerebellum and mesencephalon. No correlations were found with clinical measures.

CONCLUSIONS

Findings are in accordance with several previous studies on brain structure and match functional studies that have assessed the symptomatology of anorexia nervosa, such as body image distortion and cognitive bias to food. The correlation with duration of illness supports the implication of cerebellar atrophy in the maintenance of low weight and disrupted eating behaviour and illustrates its role in the chronic phase of anorexia nervosa. The lack of other correlations suggests that these findings are not related to the presence of co-morbid disorders.

A tract-based spatial statistics study in anorexia nervosa: abnormality in the fornix and the cerebellum

There has been an increasing interest in white matter abnormalities in patients with anorexia nervosa (AN). However, to date, there have been only a few diffusion tensor imaging (DTI) studies investigating AN, and the results are inconsistent. In this study, we employed tract-based spatial statistics (TBSS), a robust technique for whole-brain analysis of DTI data, to detect white matter abnormalities in AN patients compared with healthy controls. Seventeen women with AN and 18 age matched healthy women were included. The mean body mass index of patients was 13.6 kg/m(2) (controls: 19.9 kg/m(2)). DTI data were acquired on a 3-Tesla magnetic resonance imaging system. Fractional anisotropy (FA) and mean diffusivity (MD) maps were calculated from the DTI data of each patient, and voxel-wise group comparisons of FA and MD were performed using TBSS. Compared with the healthy comparisons, the patients showed a significantly higher MD value in the fornix and lower FA value in the left cerebellum. We also found significant positive correlations between the mean FA value of the left cerebellar hemisphere cluster and BMI, as well as between the mean MD value of the cluster in the anterior body of the fornix and the duration of illness. The results suggest that the white matter abnormalities in the fornix and the cerebellum may be related to the pathophysiology of AN.

Motivational processing of food cues in anorexia nervosa: a pilot study

Current literature suggests an increased attentional bias toward food stimuli in eating-disordered individuals compared to healthy controls. In line with these research efforts, the present study aims to investigate the processing of food stimuli (enriched by emotional stimuli) between patients diagnosed for anorexia nervosa (AN) and healthy controls by means of electroencephalography. Twenty-two female adolescents (eleven AN patients vs. eleven healthy controls) were investigated. Positive event-related potentials "P300" and "late positive potential" (LPP) reflecting attentional processing (caused by motivationally relevant stimuli) were investigated during passive viewing of the food cue picture stream. This method was used for the first time in a sample of individuals with AN. As a main result, AN patients exhibited a higher amount of attentional bias in P300 and LPP, while watching food stimuli. Moreover, AN patients rated food stimuli as less pleasant. For a conclusion, there is substantial evidence pointing to an abnormal attentional brain reactivity to food pictures in AN. Therefore, food stimuli seem to be more motivationally relevant for AN patients than for healthy controls. By broadening existing knowledge, these findings might bear some implications for the treatment for AN. However, further research is recommended in order to confirm the results coming from rather limited data.

Provocation of symmetry/ordering symptoms in Anorexia nervosa: a functional neuroimaging study

Anorexia nervosa (AN), obsessive–compulsive disorder (OCD), and obsessive–compulsive personality disorder (OCPD) are often co-morbid; however, the aetiology of such co-morbidity has not been well investigated. This study examined brain activation in women with AN and in healthy control (HC) women during the provocation of symmetry/ordering-related anxiety. During provocation, patients with AN showed more anxiety compared to HCs, which was correlated with the severity of symmetry/ordering symptoms. Activation in the right parietal lobe and right prefrontal cortex (rPFC) in response to provocation was reduced in the AN group compared with the HC group. The reduced right parietal activation observed in the AN group is consistent with parietal lobe involvement in visuospatial cognition and with studies of OCD reporting an association between structural abnormalities in this region and the severity of ‘ordering’ symptoms. Reduced rPFC activation in response to symmetry/ordering provocation has similarities with some, but not all, data collected from patients with AN who were exposed to images of food and bodies. Furthermore, the combination of data from the AN and HC groups showed that rPFC activation during symptom provocation was inversely correlated with the severity of symmetry/ordering symptoms. These data suggest that individuals with AN have a diminished ability to cognitively deal with illness-associated symptoms of provocation. Furthermore, our data also suggest that symptom provocation can progressively overload attempts by the rPFC to exert cognitive control. These findings are discussed in the context of the current neurobiological models of AN.

Estrogen receptor 1 gene rs2295193 polymorphism and anorexia nervosa: new data and meta-analysis

INTRODUCTION

Estrogen plays essential roles in the regulation of food intake, adiposity, and body weight control. The estrogen alpha receptor, encoded by estrogen receptor 1 gene (ESR1), has been implicated with anorexia nervosa (AN). A previous study indicated that the rs2295193 polymorphism in ESR1 may confer a genetic susceptibility to AN.

METHODS

In a case-control study, we assessed 195 AN probands and 93 healthy controls; 99 trios were studied in a family-based association analysis through genotyping the rs2295193 polymorphism in ESR1. Additionally, we carried out a meta-analysis of the combined sample groups.

RESULTS

There were no significant differences in the genotype or allele frequencies of the rs2295193 polymorphism between the AN and control groups (Ps > 0.05). In the transmission disequilibrium test (TDT) analyses, there was no evidence for biased transmission of the G allele of rs2295193 polymorphism (P = 0.32). In female-only samples, no significant association was observed between the rs2295193 polymorphism and AN in either case-control or transmission disequilibrium test analyses (Ps > 0.05). The meta-analysis revealed that no excess of transmission of the G allele in AN families (pooled odds ratio = 1.10, P = 0.79).

DISCUSSION

Meta-analytically combined evidence from the present genotyping and the literature showed that rs2295193 polymorphism in ESR1 is not a major genetic susceptibility factor in AN.

Advances in the neurobiology of eating disorders

PURPOSE OF REVIEW

To systematize new neurobiological findings on the cause and treatment of eating disorders.

RECENT FINDINGS

The conceptual framework of the cause of eating disorders has undergone great changes in the past decades. Recently, the National Institute of Mental Health proposed a new set of criteria for research purposes--the Research Domain Criteria (RDoC). We aim to structure this study as much as possible using these constructs across biological units of analysis, summarizing new findings. Brain imaging techniques have become sophisticated in identifying brain circuits related to illness behaviour and to fundamental traits such as reward and social processing. Genetic studies have moved from candidate gene studies onto genome-wide association studies; however, the field needs to cooperate to collect larger samples in order to benefit from this approach. Hormonal changes as the results of starvation or as underlying factors for behavioural changes still receive attention in both animal and human studies. Advances made in neuropsychology show problems in cognition (set shifting and central coherence) and in other RDoC domains. Some of these findings have been translated into treatment.

SUMMARY

New biological models are being developed which explain causal and maintaining factors. The RDoC construct may be used to systematize these findings.

A systematic review of the effects of neuromodulation on eating and body weight: evidence from human and animal studies

BACKGROUND

Eating disorders (ED) are chronic and sometimes deadly illnesses. Existing treatments have limited proven efficacy, especially in the case of adults with anorexia nervosa (AN). Emerging neural models of ED provide a rationale for more targeted, brain-directed interventions.

AIMS

This systematic review has examined the effects of neuromodulation techniques on eating behaviours and body weight and assessed their potential for therapeutic use in ED.

METHOD

All articles in PubMed, PsychInfo and Web of Knowledge were considered and screened against a priori inclusion/exclusion criteria. The effects of repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation, vagus nerve stimulation (VNS) and deep brain stimulation (DBS) were examined across studies in ED samples, other psychiatric and neurological disorders, and animal models.

RESULTS

Sixty studies were identified. There is evidence for ED symptom reduction following rTMS and DBS in both AN and bulimia nervosa. Findings from studies of other psychiatric and neurological disorders and from animal studies demonstrate that increases in food intake and body weight can be achieved following DBS and that VNS has potential value as a means of controlling eating and inducing weight loss.

CONCLUSIONS

Neuromodulation tools have potential for reducing ED symptomatology and related behaviours, and for altering food intake and body weight. In response to such findings, and emerging neural models of ED, treatment approaches are highly unlikely to remain 'brainless'. More research is required to evaluate the potential of neuromodulation procedures for improving long-term outcomes in ED.

Neurocircuit function in eating disorders

OBJECTIVE

Eating disorders are serious psychosomatic disorders with high morbidity and lifetime mortality. Inadequate response to current therapeutic interventions constitutes a challenging clinical problem. A better understanding of the underlying neurobiological mechanisms could improve psychotherapeutic and drug treatment strategies.

METHOD

A review highlighting the current state of brain imaging in eating disorders related to the anxiety and pathological fear learning model of anorexia nervosa (AN) and the impulsivity model of binge eating in bulimia nervosa (BN).

RESULTS

Available neuroimaging studies in patients with acute AN primarily suggest a hyper-responsive emotional and fear network to food, but not necessarily to eating disorder-unrelated, salient stimuli. Furthermore, patients with AN show decreased activation in the ventral fronto-striatal circuits during the performance of a cognitive flexibility task. Results in patients with BN primarily suggest a hypo-responsive reward system to food stimuli, especially to taste reward. Additionally, patients with BN exhibit impaired brain activation in the inhibitory control network during the performance of general response-inhibition tasks.

DISCUSSION

Anxiety and pathological fear learning may lead to conditioned neural stimulus-response patterns to food stimuli and increased cognitive rigidity, which could account for the phobic avoidance of food intake in patients with acute AN. However, further neurobiological studies are required to investigate pathological fear learning in patients with AN. Patients with BN may binge eat to compensate for a hypo-responsive reward system. The impaired brain activation in the inhibitory control network may facilitate the loss of control over food intake in patients with BN.