Neural and behavioral effects of modification of visual attention in body dysmorphic disorder

Abstract

In individuals with body dysmorphic disorder (BDD), perceptual appearance distortions may be related to selective attention biases and aberrant visual scanning, contributing to imbalances in global vs. detailed visual processing. Treatments for the core symptom of perceptual distortions are underexplored in BDD; yet understanding their mechanistic effects on brain function is critical for rational treatment development. This study tested a behavioral strategy of visual-attention modification on visual system brain connectivity and eye behaviors. We acquired fMRI data in 37 unmedicated adults with BDD and 30 healthy controls. Participants viewed their faces naturalistically (naturalistic viewing), and holding their gaze on the image center (modulated viewing), monitored with an eye-tracking camera. We analyzed dynamic effective connectivity and visual fixation duration. Modulated viewing resulted in longer mean visual fixation duration compared to during naturalistic viewing, across groups. Further, modulated viewing resulted in stronger connectivity from occipital to parietal dorsal visual stream regions, also evident during the subsequent naturalistic viewing, compared with the initial naturalistic viewing, in BDD. Longer fixation duration was associated with a trend for stronger connectivity during modulated viewing. Those with more severe BDD symptoms had weaker dorsal visual stream connectivity during naturalistic viewing, and those with more negative appearance evaluations had weaker connectivity during modulated viewing. In sum, holding a constant gaze on a non-concerning area of one's face may confer increased communication in the occipital/parietal dorsal visual stream, facilitating global/holistic visual processing. This effect shows persistence during subsequent naturalistic viewing. Results have implications for perceptual retraining treatment designs.

Fig. 1. fMRI task paradigm.

Four color photos of participants’ own faces at different, standardized angles were captured before the MRI session. A blocked design was used for the presentation of participant’s own face and scrambled face control stimuli for both (a) natural viewing and (b) visual modulation runs. The first 4 images were participant’s faces at different angles, and the next four images were scrambled faces. Each image was presented for 3.6 s, with a brief gap of 0.7~0.8 s for changing the image. A fixation with duration of 12.2 s was shown after the stimuli. The presentation of participant’s face and scrambled face stimuli was repeated six times in a single run. The stimuli for the visual modulation run (b) had a semi-transparent crosshair between the eyes of the participants’ faces and in the center of the scrambled faces. For the visual modulation run, participants were required to maintain their gaze on the crosshair. The rationale was that fixating visual gaze on the crosshair would reduce scanning associated with piecemeal/detailed processing, and enhance holistic/global visual processing. To ensure task compliance for viewing the photos and crosshairs, gaze location was continuously monitored with the camera by the experimenters during the scan. Informed consent was obtained for publication of the image for the volunteer in the figure.

Fig. 2. Brain Connectivity Analysis Workflow.

a Locations of the 14 spherical ROIs used for dynamic effective connectivity analysis, overlaid on a brain surface with lateral and ventral views. These included 2 ROIs in V1 [bilateral calcarine], 6 ROIs in VVS [bilateral inferior occipital gyrus (IOG), fusiform gyrus (FG), and inferior temporal gyrus (ITG)], and 6 ROIs in DVS [bilateral superior occipital gyrus (SOG), inferior parietal lobule (IPL), and superior parietal lobule (SPL)]. The nomenclature is based on Eickhoff-Zilles macro labels from N27, implemented in AFNI. All spheres had a radius of 5 mm and the center-of-mass coordinates obtained from the clusters are x, y and z in the MNI space. This panel was prepared using BrainNet Viewer [70]. b Diagram demonstrating the dynamic effective connectivity analysis workflow used to estimate the directional connectivity value from task fMRI data. Effective connectivity (EC) matrices, estimated for each time point, were pooled across task blocks of viewing one’s own face to derive the final EC estimate for each selected connection. *Note: Informed consent was obtained for publication of the volunteer’s photo in the figure.

Fig. 3. Brain Connectivity in the Dorsal Visual Stream (DVS) in Body Dysmorphic Disorder (BDD) Participants.

Means of dynamic effective connectivity for the (a) DVS_Lower and (b) DVS_Higher in the BDD group with the NMN and NNM orders. Brain graphs are presented above violin plots in which the thickness of the arrows indicates the relative changes of the mean dynamic effective connectivity values across runs. The participants randomized to the NMN order received natural viewing (N), modulated viewing (M), and then natural viewing (N) as the 1st, 2nd, and 3rd runs; those randomized to the NNM order received natural viewing (N), a second natural viewing (N), and then modulated viewing (M), as the 1st, 2nd, and 3rd runs. The p-values were Bonferroni corrected.

Fig. 4. Brain Connectivity and Clinical Symptom Associations.

Correlations between mean dynamic effective connectivity (DEC) from occipital to parietal regions in the dorsal visual stream and clinical measures across BDD participants during the first naturalistic viewing, the second naturalistic viewing, and the modulated viewing.