Abnormalities of object visual processing in body dysmorphic disorder

Abstract

Background: Individuals with body dysmorphic disorder (BDD) may have perceptual distortions for their appearance. Previous studies suggest imbalances in detailed relative to configural/holistic visual processing when viewing faces. No study has investigated the neural correlates of processing non-symptom-related stimuli. The objective of this study was to determine whether individuals with BDD have abnormal patterns of brain activation when viewing non-face/non-body object stimuli.

Method: Fourteen medication-free participants with DSM-IV BDD and 14 healthy controls participated. We performed functional magnetic resonance imaging (fMRI) while participants matched photographs of houses that were unaltered, contained only high spatial frequency (HSF, high detail) information or only low spatial frequency (LSF, low detail) information. The primary outcome was group differences in blood oxygen level-dependent (BOLD) signal changes.

Results: The BDD group showed lower activity in the parahippocampal gyrus, lingual gyrus and precuneus for LSF images. There were greater activations in medial prefrontal regions for HSF images, although no significant differences when compared to a low-level baseline. Greater symptom severity was associated with lower activity in the dorsal occipital cortex and ventrolateral prefrontal cortex for normal spatial frequency (NSF) and HSF images.

Conclusions: Individuals with BDD have abnormal brain activation patterns when viewing objects. Hypoactivity in visual association areas for configural and holistic (low detail) elements and abnormal allocation of prefrontal systems for details are consistent with a model of imbalances in global versus local processing. This may occur not only for appearance but also for general stimuli unrelated to their symptoms.

Fig. 1. Example houses stimuli

Fig. 2. Significant differences in regional brain activity between BDD and healthy control groups

a) Lesser activation for BDD relative to control participants (blue) for low spatial frequency (LSF) stimuli in the left lingual gyrus and right precuneus (top image), and left parahippocampal gyrus and left hippocampal gyrus (middle image). There was greater activation for BDD than control participants (orange) for high spatial frequency (HSF) stimuli in left frontal pole (middle image), left superior frontal gyrus (not shown), and right anterior cingulate gyrus and right paracingulate gyrus (bottom image). (See Table 2 for list of all unique local maxima). b) Percent signal changes for several regions found to be significant between groups in the voxelwise analysis for LSF (top) and HSF (bottom) stimuli.

Fig. 3. Percent signal change as a function of symptom severity

Percent signal change (y axis) in regions found to be significantly associated with symptom scores on the body dysmorphic disorder version of the Yale-Brown Obsessive Compulsive Scale (BDD YBOCS) (x axis) for a) NSF – normal spatial frequency; and b) HSF – high spatial frequency images. No regions were significantly associated with LSF – low spatial frequency – images. (Note that in Fig. 3b the left lateral occipital cortex, right cuneus, and left occipital pole are not depicted because the local max were on cortical surface regions such that spherical ROI extraction for percent signal change would not be valid).