Friday, December 07, 2007

The Trouble With Bodies

You think you're yourself, but there are other persons in you.

In the funhouse mirror-room you can't see yourself go on forever, because no matter how you stand, your head gets in the way.


-- John Barth, Lost in the Funhouse
Individuals with body dysmorphic disorder (BDD) have a distorted body image that reaches criteria for a DSM IV psychiatric disorder. They are extremely critical of their physical appearance, despite the fact that there may be no noticeable disfigurement or defect.

A recent neuroimaging study examined possible neural correlates of this distorted self-image (Feusner et al., 2007). The participants were 12 people with BDD (10 women, 2 men1) and a set of well-matched controls. For this particular experiment, the focus was on faces, not bodies. The authors note that supposed defects in the face and head are among the most common preoccupations in BDD (Phillips, 2005).2

Drawing on neuropsychological evidence that these individuals are abnormally focused on details when copying and recalling the Rey-Osterrieth Complex Figure,3 along with the obvious propensity to perceive distortions in pictures of their own face, the authors manipulated the spatial frequency information contained in the face stimuli (through filtering, shown below). Participants viewed triplets of normal, LSF, or HSF face stimuli and performed a matching task.

Figure 1 (Feusner et al., 2007). Face stimuli. HSF indicates high spatial frequency; LSF, low spatial frequency; and NSF, normal spatial frequency. (On reproduction, the HSF image in this figure lost some of the detail that was visible in the experiment.)

Previous studies have shown that global "configural" information is contained in LSF, whereas local "featural" information, such as details about the eyes, nose, and mouth, is contained in HSF (e.g., Goffaux et al., 2005). In general, the right hemisphere is thought to be better at the former, and the left hemisphere at the latter. Were there differences between the BDD and control groups in the present study?
The BDD group demonstrated more left-sided activations in lateral aspects of the prefrontal and temporal cortices for all tasks, as well as dorsal anterior cingulate activity for the LSF task. The control group demonstrated this pattern only for the HSF task, suggesting that subjects with BDD use a similar network for processing NSH and LSF faces that control subjects use only for HSF faces. These laterality patterns suggest a bias for local, or detail, processing over global processing of faces for subjects with BDD. In addition, the BDD group showed abnormal activation of the amygdalae for HSF and LSF face tasks. We did not find differences in early ventral or dorsal visual stream regions as hypothesized; rather, the differences found are in regions that may represent later stages of visual processing or top-down effects.
Basically, for HSF stimuli, the BDD group had greater activation in the left middle and inferior temporal gyri than controls. More interestingly, for LSF stimuli, they showed greater activation in left-sided temporal-parietal regions and left inferior frontal gyrus than controls. This suggests the problem is with preferential attention to local aspects of faces, rather than an issue in the visual processing stream itself. In the future, it would be interesting to examine activation to the BDD subjects' own face, as well as other body parts perceived to be defective.


When you're lost, the smartest thing to do is stay put till you're found, hollering if necessary. But to holler guarantees humiliation as well as rescue; keeping silent permits some saving of face--you can act surprised at the fuss when your rescuers find you and swear you weren't lost, if they do. What's more you might find your own way yet, however belatedly.

-- John Barth, Lost in the Funhouse

Credits: Funhouse graphics and Barth quotes are from the website of the Florida Research Ensemble (Professor Gregory L. Ulmer et al.).


Footnotes

1 However, there may not be much of a gender discrepancy in the general BDD population, according to the Body Image Program at Butler Hospital in Rhode Island).

2 Dr. Katharine Phillips et al. have compiled a list of the most commonly disliked areas in a group of over 500 BDD patients.

3 Rey-Osterrieth Complex Figure.



References

Feusner JD, Townsend J, Bystritsky A, Bookheimer S (2007). Visual Information Processing of Faces in Body Dysmorphic Disorder. Arch Gen Psychiatry 64:1417-1425.

CONTEXT: Body dysmorphic disorder (BDD) is a severe psychiatric condition in which individuals are preoccupied with perceived appearance defects. Clinical observation suggests that patients with BDD focus on details of their appearance at the expense of configural elements. This study examines abnormalities in visual information processing in BDD that may underlie clinical symptoms. OBJECTIVE: To determine whether patients with BDD have abnormal patterns of brain activation when visually processing others' faces with high, low, or normal spatial frequency information. DESIGN: Case-control study. SETTING: University hospital. PARTICIPANTS: Twelve right-handed, medication-free subjects with BDD and 13 control subjects matched by age, sex, and educational achievement. Intervention Functional magnetic resonance imaging while performing matching tasks of face stimuli. Stimuli were neutral-expression photographs of others' faces that were unaltered, altered to include only high spatial frequency visual information, or altered to include only low spatial frequency visual information. Main Outcome Measure Blood oxygen level-dependent functional magnetic resonance imaging signal changes in the BDD and control groups during tasks with each stimulus type. RESULTS: Subjects with BDD showed greater left hemisphere activity relative to controls, particularly in lateral prefrontal cortex and lateral temporal lobe regions for all face tasks (and dorsal anterior cingulate activity for the low spatial frequency task). Controls recruited left-sided prefrontal and dorsal anterior cingulate activity only for the high spatial frequency task. CONCLUSIONS: Subjects with BDD demonstrate fundamental differences from controls in visually processing others' faces. The predominance of left-sided activity for low spatial frequency and normal faces suggests detail encoding and analysis rather than holistic processing, a pattern evident in controls only for high spatial frequency faces. These abnormalities may be associated with apparent perceptual distortions in patients with BDD. The fact that these findings occurred while subjects viewed others' faces suggests differences in visual processing beyond distortions of their own appearance.


Goffaux V, Hault B, Michel C, Vuong QC, Rossion B (2005). The respective role of low and high spatial frequencies in supporting configural and featural processing of faces. Perception 34:77-86.

Phillips KA. (2005). The Broken Mirror. New York, NY: Oxford University Press.

Self-portrait in a Broken Mirror, is that bad luck?
by Steve Smart
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