Learning of the same task subserved by substantially different mechanisms between patients with body dysmorphic disorder and healthy individuals

Abstract

It has remained unclear whether individuals with psychiatric disorders involving altered visual processing employ similar neuronal mechanisms during perceptual learning of a visual task. We investigated this question by training patients with body dysmorphic disorder, a psychiatric disorder characterized by distressing or impairing preoccupation with nonexistent or slight defects in one's physical appearance, and healthy controls on a visual detection task for human faces with low spatial frequency components. Brain activation during task performance was measured with functional magnetic resonance imaging before the beginning and after the end of behavioral training. Both groups of participants improved performance on the trained task to a similar extent. However, neuronal changes in the fusiform face area were substantially different between groups such that activation for low spatial frequency faces in the right fusiform face area increased after training in body dysmorphic disorder patients but decreased in controls. Moreover, functional connectivity between left and right fusiform face area decreased after training in patients but increased in controls. Our results indicate that neuronal mechanisms involved in perceptual learning of a face detection task differ fundamentally between body dysmorphic disorder patients and controls. Such different neuronal mechanisms in body dysmorphic disorder patients might reflect the brain's adaptations to altered functions imposed by the psychiatric disorder.

Keywords: body dysmorphic disorder; fusiform face area; plasticity; visual perceptual learning.

Fig. 1

Experiment design. A) Experiment timeline. The pretest and posttest stages were conducted during MRI scanning, whereas the remaining stages were conducted outside the scanner. B) Examples of 4 types of visual stimuli used during the sensitivity measurement in the pretest and posttest stages. The stimuli consisted of LSF faces, HSF faces, LSF houses and HSF houses, from left to right. C) Example of the procedure of a 2IFC task trial conducted during the pretest, posttest and training stages in the temporal order of first interval (200 ms), interstimulus interval (600 ms), second interval (200 ms), and response (1000 ms). D) Localization of the FFA in the left and right inflated hemispheres of a representative participant (view of the brain from below).

Fig. 2

Behavioral results. Mean ± standard-error-of-the-mean (SEM) performance change across patients with BDD and healthy controls. Zero on the y-axis corresponds to performance before training. Values above zero on the y-axis indicate that performance improved after training. The results showed that both groups improved on the detection of LSF faces through training. The improvement did not transfer to other untrained conditions. ^*P < 0.05.

Fig. 3

Functional MRI results.A) Mean ± SEM BOLD beta index of FFA right lateralization for comparison between LSF and HSF faces across BDD patients and healthy controls. Greater values on the y-axis correspond to greater FFA right lateralization. B) Same as A) but for the comparison between LSF and HSF houses. C) Correlation between performance improvement and BOLD beta index of FFA right lateralization across BDD patients. Each dot shows the result from a different participant. D) Same as C) but across healthy controls. ^*P < 0.05.

Fig. 4

Correlation results. A) Correlation between pretest performance and BOLD beta index of FFA right lateralization across BDD patients. Each dot shows the result from a different participant. B) Same as A), but across healthy controls. C) Correlation between posttest performance and BOLD beta index of FFA right lateralization across BDD patients. Otherwise, same as A). D) Same as C), but across healthy controls.

Fig. 5

Mean ± SEM change in fisher-transformed correlation coefficient between left and right FFA across BDD patients and healthy controls. Greater values on the y-axis correspond to greater connectivity. ^**P < 0.01; ^*P < 0.05.