Electrophysiological evidence for an attentional bias in processing body stimuli in bulimia nervosa

Temporal dynamics of spatial attentional biases toward weight-related words among females with weight dissatisfaction

Attentional bias toward weight-related stimuli plays a crucial role in the development and maintenance of body image disturbances. However, the temporal dynamics of attentional biases responsible for the previously reported behavioral effects caused by the task-irrelevant but spatial-relevant weight-related stimuli presented in the peripheral visual field among females with high weight dissatisfaction (HWD) remain unclear. The present study combined the modified dot-probe task and event-related potentials to explore the temporal dynamics of spatial attentional biases toward weight-related words among females with HWD. The results showed significantly larger N2pc amplitudes were elicited by fat-related and thin-related words than neutral words only in the HWD group. Moreover, only fat-related words elicited a significant PD for the HWD group, and the PD amplitudes were larger in the HWD group than in the control group. These findings revealed that weight-related words initially captured spatial allocation among females with HWD, and then fat-related words were actively suppressed after the initial capturing.

Processing of food stimuli in anorexia nervosa: An ERP-study comparing adolescents and adults

BACKGROUND

Anorexia nervosa (AN) is associated with altered processing of disorder-relevant stimuli. Event-related potentials (ERP) - such as the Late Positive Potential (LPP) - give information about the underlying mechanisms of central nervous stimulus processing.

METHODS

Patients with AN (22 adolescents, 23 adults) and healthy controls (HCs; 17 adolescents, 24 adults) were included. Neutral, low, and high calorie food-images were rated for valence and arousal; EEG activity was recorded and LPPs (early: 350-700 ms; late: 800-1200 ms) were extracted. Effects of patient status, age group, and stimulus category were analyzed via mixed 2 × 2 × 3-AN(C)OVAs.

RESULTS

Patients with AN rated high calorie stimuli lower in valence and higher in arousal than HCs. Controlling for hunger, food stimuli elicited higher early LPPs than neutral ones in patients and HCs. For the late LPP, patients with AN showed larger amplitudes.

CONCLUSION

Results suggest a highly automatic attentional bias towards low-calorie foods. Patients with AN seem to have more intense cognitive processing independent of stimulus material. More research is needed to validate and clarify differences between early and late LPP measures as well as the operationalization and relevance of hunger status.

Attentional biases toward auditory weight-related information among females with weight dissatisfaction

Although there is substantial evidence of visual attentional biases in processing weight-related information among individuals with weight dissatisfaction, few studies have examined auditory attentional biases in these individuals. The identification of attentional biases may provide an impetus for interventions to reduce distress, negative body image, and pathological eating patterns among weight-dissatisfied individuals. Therefore, the present study aimed to investigate the attentional biases, as well as the neural consequences, toward auditory weight-related information among weight-dissatisfied young females. In this experiment, young female participants were assigned to an experimental group with high weight dissatisfaction (HWD) and a control group with low weight dissatisfaction (LWD) according to the levels of weight dissatisfaction. Using a spatial cueing paradigm, auditory fatness-related, thinness-related, and neutral household words were presented laterally as cue stimuli, followed by visual stimuli presented at either the cued or uncued location. The results revealed that auditory fatness-related words elicited significantly larger N2ac amplitudes than auditory thinness-related and neutral words in the HWD group. However, for the LWD group, thinness-related words elicited a significantly larger N2ac than fatness-related and neutral words. These results suggest an orienting attentional bias toward auditory fatness-related body words among females with HWD and an orienting attentional bias toward auditory thinness-related words among females with LWD.

You See What You Smell: Preferential Processing of Chemosensory Satiety Cues and Its Impact on Body Shape Perception

The current study examines neural responses to satiety- and fasting-related volatiles and their effect on the processing of body shapes. Axillary sweat was sampled with cotton pads from 10 individuals after 12 h of fasting, and after having consumed a standard breakfast. Pure cotton pads served as the control. The chemosensory stimuli were presented to 20 participants (via a constant-flow olfactometer) exclusively, and additionally as context to images of overweight and underweight avatars. EEG was recorded (61 electrodes), and chemosensory (CSERPs; P1, N1, P2, P3) and visual event-related potentials (VERPs; N1, P2, P3a, P3b) were analyzed. The amplitudes of all positive CSERP components differed more strongly from cotton in response to chemosensory satiety cues as compared to fasting cues (P1: p = 0.023, P2: p = 0.083, P3: p = 0.031), paralleled by activity within the middle frontal and temporal gyrus. Overweight compared to underweight body shapes tended to elicit larger VERP P2 amplitudes (p = 0.068), and chemosensory satiety cues amplified the VERP amplitudes in response to any body shape (P2, P3a, P3b; all p_s ≤ 0.017) as compared to the cotton control. The results indicate that chemosensory satiety cues transmit complex social information, overriding the processing of analogous visual input.

A Systematic Review of Electrophysiological Findings in Binge-Purge Eating Disorders: A Window Into Brain Dynamics

Binge-purge eating disorders (BP-ED), such as bulimia nervosa and binge eating disorder, may share some neurobiological features. Electroencephalography (EEG) is a non-invasive measurement modality that may aid in research and diagnosis of BP-ED. We conducted a systematic review of the literature on EEG findings in BP-ED, seeking to summarize and analyze the current evidence, as well as identify shortcomings and gaps to inform new perspectives for future studies. Following PRISMA Statement recommendations, the PubMed, Embase, and Web of Science databases were searched using terms related to “electroencephalography” and “binge-purge” eating disorders. Of 555 articles retrieved, 15 met predefined inclusion criteria and were included for full-text analysis. Eleven studies investigated EEG by means of event-related potentials (ERP) in BP-ED individuals: 7 using eating disorder-related stimuli (i.e., food, body image) and 4 using non-eating disorder-related stimuli (i.e., facial expressions or auditory clicks). These studies found significant differences in the N200, P200, P300, and LPP components in BP-ED participants compared to controls, indicating that this population exhibits impairments in selective attention, attentional allocation/processing, and allocation of motivational or emotion-based attention. Five studies investigated EEG using frequency analysis; reporting significant differences in beta activity in fronto-temporal and occipito-temporo-parietal areas in BP-ED individuals compared to controls, revealing a dysfunctional brain network. However, the small number of studies, the heterogeneity of samples, study paradigms, stimulus types, and the lack of an adequate assessment of neuropsychological parameters are some limitations of the current literature. Although some EEG data are promising and consistent with neuroimaging and neuropsychological findings in individuals with BP-ED, future studies need to overcome current methodological shortcomings.

Neural Processing of Food and Erotic Cues in Bulimia Nervosa

OBJECTIVE

Event-related brain potential (ERP) studies have shown that bulimia nervosa (BN) is associated with facilitated processing of disorder-specific stimuli, visible in altered early components during presentation of food cues and bodies varying in size. Less is known about BN and late ERPs, typically less influenced by perceptual features and regarded as more reliable indices of motivational relevance. The purpose of this study was to use the late positive potential (LPP) to investigate the motivational significance of BN-relevant stimuli.

METHODS

Highly salient stimuli, such as pictures of personal binge foods and images that are pleasant, neutral, and unpleasant (e.g., human attacks) were presented to 24 women with bulimia and 24 healthy women (19.7 ± 2.1 and 20.5 ± 2.6 years, respectively). Pictures of erotic couples, previously shown to prompt the greatest appetitive reactions in healthy women, were used as pleasant cues. Based on BN aversion to body cues, we hypothesized that the motivational significance of erotic cues could be increased in bulimic women.

RESULTS

Consistent with the literature, the LPP was modulated by the salience of the pictures (F(2.8,130.7) = 24.6, p < .001). An additional interaction with diagnostic group (F(2.8,130.7) = 2.8, p = .047) indicated that bulimic women showed a larger LPP than healthy controls during pictures displaying binge foods (p = .037) and erotic couples (p = .031).

CONCLUSIONS

The findings provide objective evidence that BN is characterized by dysregulated emotional processing that is not limited to food cues. The implications are discussed within a transdiagnostic perspective on food-related disorders.

The Representation of Body Size: Variations With Viewpoint and Sex

Perceived body size is a fundamental construct that reflects our knowledge of self and is important for all aspects of perception, yet how we perceive our bodies and how the body is represented in the brain is not yet fully understood. In order to understand how the brain perceives and represents the body, we need an objective method that is not vulnerable to affective or cognitive influences. Here, we achieve this by assessing the accuracy of full-body size perception using a novel psychophysical method that taps into the implicit body representation for determining perceived size. Participants were tested with life-size images of their body as seen from different viewpoints with the expectation that greater distortions would occur for unfamiliar views. The Body Shape Questionnaire was also administered. Using a two-alternative forced choice design, participants were sequentially shown two life-size images of their whole body dressed in a standardized tight-fitting outfit seen from the front, side, or back. In one image, the aspect ratio (with the horizontal or vertical dimension fixed) was varied using an adaptive staircase, while the other was undistorted. Participants reported which image most closely matched their own body size. The staircase honed in on the distorted image that was equally likely as the undistorted photo to be judged as matching their perception of themselves. From this, the perceived size of their internal body representation could be calculated. Underestimation of body width was found when the body was viewed from the front or back in both sexes. However, females, but not males, overestimated their width when the body was viewed from the side. Height was perceived accurately in all views. These findings reveal distortions in perceived size for healthy populations and show that both viewpoint and sex matter for the implicit body representation. Though the back view of one’s body is rarely–if ever–seen, perceptual distortions were the same as for the front view. This provides insight into how the brain might construct its representation of three-dimensional body shape.

Distinct neural response to visual perspective and body size in the extrastriate body area

Neuroimaging research has independently implicated the extrastriate body area (EBA) in distinguishing between different visual perspectives and morphologies of bodies within visual processing. However, the combined processing of these physical attributes towards neural EBA response remains unclear, and may be crucial in influencing higher-order, aesthetic evaluation of bodies. Indeed, EBA alterations amongst eating disorder patients have been associated with disturbances in body image, and disruption to EBA activity amongst healthy individuals has been shown to influence aesthetic evaluations made towards bodies. Therefore, the present study used images of slim and large female bodies viewed from egocentric and allocentric perspectives, to investigate neural EBA response amongst healthy females (N = 30). In addition, participants provided behavioural aesthetic and weight evaluations of all model stimuli. Results revealed an interaction, bilaterally, between visual perspective and body size towards EBA activity, with multi-voxel pattern analysis revealing distinct neural patterns between the four conditions. However, EBA activity did not relate to non-clinical eating disorder psychopathology. No direct relationship was found between EBA activity and behavioural evaluations of model stimuli; however, a whole brain analysis revealed that higher-order, prefrontal regions were associated with cognitive evaluations of large bodies. Taken together, our results suggest that the EBA is an integral core region in discriminating between multiple physical attributes of the body, which is likely to provide important information to higher-order brain regions which make aesthetic evaluations towards bodies.

Investigating the Components of Body Image Disturbance Within Eating Disorders

Body image disturbance has been highlighted as a common characteristic within the development and maintenance of clinical eating disorders (EDs), represented by alterations in an individual's bodily experience. However, whilst the perceptual stability of the sense of body ownership has been investigated in ED patients, the stability of the sense of body agency in those with ED is yet to be examined. Therefore, body ownership and body agency were investigated using the moving rubber hand illusion, alongside measures of explicit and implicit body satisfaction. Furthermore, with evidence demonstrating a direct link between perceptual and cognitive-affective components of body image in the healthy population, the relationship between measures of body perception and body satisfaction was investigated. Results showed that both ED and healthy individuals displayed a similar subjective experience of illusory ownership and agency towards the fake hand, following voluntary movement. However, whilst both groups initially overestimated their own hand width prior to the illusion, the ED group displayed a significant reduction in hand size estimation following the illusion, which was not matched to the same degree in healthy individuals. In addition, ED individuals displayed a significantly lower body satisfaction compared with healthy females, on both an explicit and implicit level. Such implicit outcomes were shown to be driven specifically by a weaker association between the self and attractiveness. Finally, a significant relationship was observed between specific perceptual measures and implicit body satisfaction, which highlights the important link between perceptual and cognitive-affective components of one's body image. Together, such findings provide a useful foundation for further research to study the conditions in which these two components relate with regard to body image and its disturbance, particularly in relation to the prognosis and treatment of EDs.

Evidence for altered configural body processing in women at risk of disorders characterized by body image disturbance

Two studies were conducted to assess appearance-related visual processing mechanisms in populations at risk of disorders characterized by body image disturbance. Using inverted stimuli, Experiment 1 assessed visual processing mechanisms associated with body, face, and house viewing in adolescents. Experiment 2 applied the same protocol to assess appearance-related configural processing in high- and low-risk adolescent women, and women recovering from disorders characterized by body image disturbance. Experiment 1 found evidence for typical configural face and body processing, although adolescent women reported higher levels of body image concern (BIC) and self-objectified to a greater extent than adolescent men. In Experiment 2, typical body inversion effects were seen in the low-risk group, whilst there was some evidence to suggest a disruption to the configural processing of body stimuli in high-risk adolescents and in women recovering from body image disorders. Women in recovery were also quicker to respond to all stimuli, whilst high-risk adolescents took longer to respond to bodies than to other stimuli. Configural face processing was intact in all groups, and effects did not directly relate to BIC or self-objectification. These findings have implications for future research looking to inform early interventions and treatment, suggesting that there could be a tendency to visually process individual body parts at the expense of the whole-body form in women at risk of developing body image disorders, as well as those in recovery.

Selective attentional biases towards a self-related facial feature among orthognathic patients

The present study aimed to determine what kind of face and which area of the face (eyes or mouth) rapidly capture attention among patients with dentomaxillofacial deformities (DDs). In the present experiments, faces were categorized as highly or lowly attractive (HA and LA, respectively) and as a face with dentomaxillofacial deformities (DD face). A dot-probe task and a change-detection task were utilized to examine the attentional bias to the faces and facial features, respectively. In Study 1, we found that DD patients showed an attentional bias to DD male faces compared with HA male faces, while controls showed an opposite attentional pattern. In Study 2, we found that patients responded faster to the changes in the mouths of DD male faces than those of HA and LA faces. Moreover, patients paid less attention to the mouths of HA faces than to the region of the eyes, and they paid less attention than did the controls. These results indicated that DD patients selectively directed their attention to DD male faces and the mouths of these faces. These findings were not evident in female faces. Furthermore, patients showed avoidance of the mouths of HA faces regardless of the gender of the faces.

Sustained hypervigilance for one's own body in women with weight and shape concerns: Competition effects in early visual processing investigated by steady-state visual evoked potentials (SSVEP)

This study aimed to analyze the covert attentional time course in early body processing areas in women with high body concerns. Therefore, we assessed the effect of pictures of one's own body and other bodies as distractions from a demanding dot detection task in 24 women with low and 20 women with high body concerns. Participants were instructed to attend to flickering dots eliciting steady-state visual evoked potentials (SSVEP) measured by EEG. Both groups showed a sustained SSVEP amplitude reduction, which was more pronounced for average-weight or thin bodies than for overweight bodies. For women with high body concerns, SSVEP amplitudes decreased more in the case of pictures of their own body. The results indicate covert vigilance and maintenance patterns for body stimuli, especially for bodies representing the thin ideal. Moreover, women with high body concerns attend more to information about their own body, which might maintain body dissatisfaction.

Double standards in body evaluation? How identifying with a body stimulus influences ratings in women with anorexia nervosa and bulimia nervosa

OBJECTIVE

Women with eating disorders (ED) evaluate their own body more negatively than do women without ED. However, it is unclear whether this negative rating is due to objective bodily features or different standards for one's own body and others' bodies. Therefore, the purpose of this study was to examine whether women with ED apply double standards when rating bodies by disentangling the objective features of one's own body from the feelings of ownership.

METHOD

We presented n = 34 women with anorexia nervosa, n = 31 women with bulimia nervosa, and n = 114 healthy controls with pictures of thin, average-weight, overweight, athletic, and hypermuscular bodies. Identity was manipulated by showing each body once with the participant's own face and once with the face of another woman. Participants were instructed to report their emotional state according to valence and arousal and to rate body attractiveness, body fat, and muscle mass.

RESULTS

Women with anorexia nervosa and bulimia nervosa displayed greater self-deprecating double standards in body fat rating than did women without ED, as quantified by the difference between the ratings of the same body with one's own versus another woman's face. Double standards reflected in valence, arousal and attractiveness ratings were significantly more pronounced in women with anorexia nervosa than in women without ED.

DISCUSSION

The double standards found may be due to an activation of dysfunctional self-related body schemata, which distort body evaluation depending on identity. Double standards related to body fat were characteristic for women with ED, but not for women without ED.

Early visual ERPs show stable body-sensitive patterns over a 4-week test period

Event-related potential (ERP) studies feature among the most cited papers in the field of body representation, with recent research highlighting the potential of ERPs as neuropsychiatric biomarkers. Despite this, investigation into how reliable early visual ERPs and body-sensitive effects are over time has been overlooked. This study therefore aimed to assess the stability of early body-sensitive effects and visual P1, N1 and VPP responses. Participants were asked to identify pictures of their own bodies, other bodies and houses during an EEG test session that was completed at the same time, once a week, for four consecutive weeks. Results showed that amplitude and latency of early visual components and their associated body-sensitive effects were stable over the 4-week period. Furthermore, correlational analyses revealed that VPP component amplitude might be more reliable than VPP latency and specific electrode sites might be more robust indicators of body-sensitive cortical activity than others. These findings suggest that visual P1, N1 and VPP responses, alongside body-sensitive N1/VPP effects, are robust indications of neuronal activity. We conclude that these components are eligible to be considered as electrophysiological biomarkers relevant to body representation.

Cue reactivity towards bodies in anorexia nervosa - common and differential effects in adolescents and adults

BACKGROUND

Aberrant reward mechanisms with regard to slim body shapes are discussed in patients with anorexia nervosa (AN). The aim of the present study was to examine of cue reactivity toward body shapes in AN via the late positive potential (LPP), an event-related electroencephalography (EEG) component. By including adolescents and adults, aspects of development and chronification could be studied (2 × 2 design).

METHODS

Thirty-two female AN patients (19 adolescents and 13 adults) and 37 control participants (16 adolescents and 21 adults) were included. Standardized photographic stimuli showing women's bodies in underwear from five body mass index (BMI) categories (extremely underweight to extremely overweight) were presented. During picture evaluation, EEG activity was recorded (10-20 system). The LPP was measured in two time windows characterized by different topographies (450-700 ms: posterior; 1000-1300 ms: central).

RESULTS

Regarding the posterior component, LPP amplitudes were clearly reduced in adult but not in adolescent patients; for both time windows the LPP showed differential patterns over BMI categories for patients and controls. Regarding the central component, a highly significant linear decrease from extremely underweight to extremely overweight body shapes was revealed in patients and no significant modulation in control participants.

CONCLUSIONS

Adolescent and adult patients show increased sustained attention toward extremely underweight bodies. In chronically ill patients, this bias appears to be accompanied by generally reduced automatic attention. The LPP findings provide a differentiated picture of aberrant cue reactivity which could be interpreted as motivated attention toward body shapes in AN.

A systematic review of attentional biases in disorders involving binge eating

OBJECTIVE

Attentional bias (AB) may be one mechanism contributing to the development and/or maintenance of disordered eating. AB has traditionally been measured using reaction time in response to a stimulus. Novel methods for AB measurement include eye tracking to measure visual fixation on a stimulus, and electroencephalography to measure brain activation in response to a stimulus. This systematic review summarizes, critiques, and integrates data on AB gathered using the above-mentioned methods in those with binge eating behaviors, including binge eating, loss of control eating, and bulimia nervosa.

METHOD

Literature searches on PubMed and PsycInfo were conducted using combinations of terms related to binge eating and biobehavioral AB paradigms. Studies using AB paradigms with three categories of stimuli were included: food, weight/shape, and threat. For studies reporting means and standard deviations of group bias scores, Hedges' g effect sizes for group differences in AB were calculated.

RESULTS

Fifty articles met inclusion criteria and were reviewed. Individuals who binge eat in the absence of compensatory behaviors show an increased AB to food cues, but few studies have examined such individuals' AB toward weight/shape and threatening stimuli. Individuals with bulimia nervosa consistently show an increased AB to shape/weight cues and socially threatening stimuli, but findings for AB to food cues are mixed.

DISCUSSION

While there are important research gaps, preliminary evidence suggests that the combination of AB to disorder-specific cues (i.e., food and weight/shape) and AB toward threat may be a potent contributor to binge eating. This conclusion underscores previous findings on the interaction between negative affect and AB to disorder-specific cues. Recommendations for future research are provided.

Where Do You Look? Visual Attention to Human Bodies across the Weight Spectrum in Individuals with Normal Weight or with Obesity

OBJECTIVE

We investigated how individuals with normal weight (NW) versus individuals with obesity (OB) visually explore human bodies varying in BMI.

METHODS

16 OB (BMI 37.5 ± 7.7 kg/m²) and 35 NW (BMI 21.5 ± 1.6 kg/m²) visually explored 35 natural photographs and 25 avatars depicting male and female bodies ranging from normal weight to obesity. Gaze behaviour was assessed using eye tracking technology. Additionally, participants rated the attractiveness of all body stimuli.

RESULTS

A comparison of the displayed gaze behaviour shown by both participant weight classes indicates that regarding visual stimuli of obese natural bodies, all participants (OB + NW) looked at the waist longer, whereas regarding visual stimuli of normal-weight bodies, all participants viewed the head longer. Overall, OB spent less time looking at the bodies than NW. All participants rated normal-weight bodies as more attractive than obese bodies. However, the NW sample rated the depicted obese bodies as even less attractive than the OB sample did.

CONCLUSIONS

The BMI of the explored body, but not the observer's BMI, produces differences in the visual exploration of human bodies. The displayed exploration pattern of obese bodies can cautiously be interpreted as a 'de-individualised' and 'obesity-focused' perception. This tendency may prove in close relationship with the negative cultural views on obesity.

Perceived face size in healthy adults

Perceptual body size distortions have traditionally been studied using subjective, qualitative measures that assess only one type of body representation-the conscious body image. Previous research on perceived body size has typically focused on measuring distortions of the entire body and has tended to overlook the face. Here, we present a novel psychophysical method for determining perceived body size that taps into implicit body representation. Using a two-alternative forced choice (2AFC), participants were sequentially shown two life-size images of their own face, viewed upright, upside down, or tilted 90°. In one interval, the width or length dimension was varied, while the other interval contained an undistorted image. Participants reported which image most closely matched their own face. An adaptive staircase adjusted the distorted image to hone in on the image that was equally likely to be judged as matching their perceived face as the accurate image. When viewed upright or upside down, face width was overestimated and length underestimated, whereas perception was accurate for the on-side views. These results provide the first psychophysically robust measurements of how accurately healthy participants perceive the size of their face, revealing distortions of the implicit body representation independent of the conscious body image.

Normal interoceptive accuracy in women with bulimia nervosa

Previous studies suggest that patients suffering from bulimia nervosa (BN) have difficulties in perceiving internal bodily signals, mostly assessed by self-report questionnaires. Whether interoception is, in this case, attenuated or not remains an open question. Therefore, interoceptive processes were examined in twenty-three patients with current BN and were compared to healthy participants. We investigated Interoceptive Accuracy (IAc) assessed by the heartbeat detection task and Interoceptive Awareness (IA) assessed by the Eating Disorder Inventory-2. Patients with BN and healthy participants did not differ in terms of IAc when controlling for BMI, depression and anxiety, whereas IA among BN patients was found to have decreased. Although IAc and IA were not related among controls, we observed an inverse correlation in BN, suggesting that an abnormal overlap between these two levels of interoceptive signal processing is present in BN. The current study introduces a new perspective concerning the role of interoceptive processes in BN and generates further questions regarding the therapeutic utility of methods targeting the interaction between different levels of interoception in the treatment of BN.