Monday, May 1, 2017

Tracking Down Body Image Distortions

Courtesy of Eating Disorders Review

Two studies examine how individual perceptions can be altered.
Body perception problems are among the most striking manifestations of anorexia nervosa (AN). In two recent studies, researchers in Australia and the US used different approaches to determine the origins of distorted body image among AN patients.
Visual adaptations after exposure
Dr. Kevin R. Brooks and colleagues at Macquarie University, Sydney, Australia, designed a unique study to test the effect of manipulated images on a group of female undergraduates (Frontiers in Neuroscience 2016; doi:10.3389/fnins.2016.00334). This is one of the few studies designed to explore how neural mechanisms affect body perception.
Dr. Brooks’ group chose 24 Caucasian female undergraduate psychology students for the experiment. First, full-body digital photos were taken of each participant. The women were photographed while standing and wearing bicycle shorts and a form-fitting top, with feet shoulder-width apart and arms straight at their sides. Then, the original photographs were manipulated in Adobe Photoshop to produce 7 final images depicting the subjects at from -30% to +30% of their original size. Weight and height were recorded to establish body mass index (BMI, kg/m2) for each participant.
Next, each student was shown a photograph of the face of another individual whose BMI and age closed matched hers. Each participant was then tested to see whether she thought the individual in the image was larger or smaller than non-manipulated images viewed at an earlier stage of the experiment. Looking at the digitally manipulated images for as little as 1 minute was enough to change the perception of images seen afterward. For example, after a student looked at images that had been manipulated to make a person appear thinner, people in non-manipulated images seemed heavier than normal.
Neural differences in self-perception during and after weight recovery
In healthy populations, several brain areas, including the medial prefrontal cortex, the posterior cingulate cortex, and the temporal parietal junction, are connected to self-perception and evaluation. Neural activations during self-perception are thought to be altered in AN patients (J Science and Neuroscience 2014; 39:178). But, does this factor normalize with recovery or do the neural activations persist?    
To answer this question, Dr. Carrie J. McAdams and colleagues traced neural pathways that they theorized affected self-perception during illness and after weight recovery among women with AN (Social Cognitive and Affective Neuroscience 2016; 1825-1851.) Dr. McAdams and her colleagues used the Social Identity V2 task (McAdams and Krawak, 2014) and the Faces task to evaluate three groups: 19 healthy women, 22 women with AN, and 18 women in long-term weight recovery after AN. The Social Identity Task involves the subject in different interactions with images of themselves, friends, and reflected images personalized with the name of a female friend. The subjects then responded to 48 statements that related to social interactions, presented three times. In the Faces task, each subject viewed 15 images of her face and 15 images of a stranger. The stranger’s images closely matched those of the subject except that the head was tilted differently in each image. Both ill and weight- recovered AN participants had substantially different medial prefrontal cortex activation as compared to controls. Compared with controls, those with AN had different performance on the Faces task. The reactions were very similar among those with restored weight and controls.
Thus, successful weight recovery from AN seems to be associated with some aspects of self-perception, but not to others. Much more needs to be learned, but both studies add hope for possible ways to better understand the complexities of and treatment for patients with AN.                                                                                                                                                                             

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