Background: Agoraphobia was described in 1871 as a condition of fear-related alterations in spatial orientation and locomotor control triggered by places or situations that might cause a patient to panic and make feel trapped. In contemporary nosology, however, this original concept of agoraphobia was split into two diagnostic entities, the modern anxiety disorder of agoraphobia consisting solely of phobic/avoidant symptoms in public spaces and the recently defined vestibular disorder of persistent postural perceptual dizziness (PPPD) characterized by dizziness and unsteadiness exacerbated by visual motion stimuli. Previous neuroimaging studies found altered brain activity and connectivity in visual-vestibular networks of patients with PPPD versus healthy controls. Neuroticism and introversion, which predispose to both agoraphobia and PPPD, influenced brain responses to vestibular and visual motion stimuli in patients with PPPD. Similar neuroimaging studies have not been undertaken in patients with currently defined agoraphobia. Given their shared history and predisposing factors, we sought to test the hypotheses that individuals with agoraphobic symptoms have alterations in visual-vestibular networks similar to those of patients with PPPD and that these alterations are influenced by neuroticism and introversion.
Methods: In the Human Connectome Project database, we matched 52 participants with sub-clinical agoraphobia and 52 control subjects without agoraphobic symptoms on 19 demographic and psychological/psychiatric variables. We then employed a graph-theoretical framework to compare resting-state functional magnetic resonance images between groups. We evaluated the interactive effects of neuroticism and introversion on the brain signatures of agoraphobia.
Results: Individuals with subclinical agoraphobia had lower global clustering, efficiency and transitivity relative to controls. They also had reduced connectivity metrics in two brain networks, one positioned to process incoming visual space-motion information, assess threat, and initiate/inhibit behavioral responses (visuospatial-emotional network) and one positioned to control and monitor locomotion (vestibular-navigational network). Introversion interacted with agoraphobic symptoms to reduce connectivity of the visuospatial-emotional network. This contrasted with previous findings of neuroticism-associated increased connectivity in a narrower visual-spatial-frontal network in patients with PPPD.
Conclusion: Functional connectivity was decreased in two brain networks in subclinical agoraphobia. These networks integrate visual vestibular and emotional response to guide movement in space.