Aberrant early visual neural activity and brain-behavior relationships in anorexia nervosa and body dysmorphic disorder

Abstract

Background: Body dysmorphic disorder (BDD) and anorexia nervosa (AN) share the clinical symptom of disturbed body image, which may be a function of perceptual distortions. Previous studies suggest visual or visuospatial processing abnormalities may be contributory, but have been unable to discern whether these occur early or late in the visual processing stream. We used electroencephalography (EEG) and visual event related potentials (ERP) to investigate early perceptual neural activity associated with processing visual stimuli.

Methods: We performed EEG on 20 AN, 20 BDD, 20 healthy controls, all unmedicated. In order to probe configural/holistic and detailed processing, participants viewed photographs of faces and houses that were unaltered or filtered to low or high spatial frequencies, respectively. We calculated the early ERP components P100 and N170, and compared amplitudes and latencies among groups.

Results: P100 amplitudes were smaller in AN than BDD and healthy controls, regardless of spatial frequency or stimulus type (faces or houses). Similarly, N170 latencies were longer in AN than healthy controls, regardless of spatial frequency or stimulus type, with a similar pattern in BDD at trend level significance. N170 amplitudes were smaller in AN than controls for high and normal spatial frequency images, and smaller in BDD than controls for normal spatial frequency images, regardless of stimulus type. Poor insight correlated with lower N170 amplitudes for normal and low spatial frequency faces in the BDD group.

Conclusions: Individuals with AN exhibit abnormal early visual system activity, consistent with reduced configural processing and enhanced detailed processing. This is evident regardless of whether the stimuli are appearance-or non-appearance-related, and thus may be a reflection of general, early perceptual abnormalities. As N170 amplitude could be a marker of structural encoding of faces, lower values may be associated with perceptual distortions and could contribute to poor insight in BDD. Future studies may explore visual ERP measures as potential biomarkers of illness phenotype.

Keywords: anorexia nervosa; body dysmorphic disorder; dorsal ventral streams; electroencephalography; visual processing.

Figure 1

Left: Example of stimuli used in the experiment, filtered to normal, high, and low spatial frequencies. Right: Task paradigm, consisting of a face or house matching task.

Figure 2

Group· averaged ERP components for Face and House Tasks. The first 50ms are the baseline period, stimulus presentation at time = 0.

Figure 3

P100 amplitudes across stimulus type (Faces/Houses), Group (AN, BDD, and Controls), and spatial frequency (LSF, Iow spatial frequency; NSF, normal spatial frequency; HSF, high spatial frequency). Asterisks denote significant group effects, p < 0.05, showing AN have smaller P100 amplitudes than BDD or controls for all image types.

Figure 4

N170 amplitudes across stimulus type (Faces/Houses), Group (AN, BDD, and Controls), and spatial frequency (LSF, Iow spatial frequency; NSF, normal spatial frequency; HSF, high spatial frequency). Asterisks denote significant group by spatial frequency effects, p < 0.05, showing AN have smaller N170 amplitudes than controls for HSF and NSF images, while BDD have smaller N170 amplitudes than controls for NSF images.

Figure 5

N170 latencies across stimulus type (Faces/Houses), Group (AN, BDD, and Controls) and spatial frequency (LSF, Iow spatial frequency; NSF, normal spatial frequency; HSF, high spatial frequency). Asterisks denote significant group effects, p < 0.05, showing AN have significantly longer N170 latencies than controls for all image types.

Figure 6

Correlations of BABS scores and N170 amplitudes for NSF and LSF faces in individuals with BDD. Lower (less negative) amplitude is associated with worse insight (higher BABS scores). ^*Survives Bonferroni corrections for multiple comparisons.