Functional neuroimaging in specific phobia

Abstract

Specific phobias (SPs) are common, with lifetime prevalence estimates of 10%. Our current understanding of their pathophysiology owes much to neuroimaging studies, which enabled us to construct increasingly efficient models of the underlying neurocircuitry. We provide an updated, comprehensive review and analyze the relevant literature of functional neuroimaging studies in specific phobias. Findings are presented according to the functional neuroanatomy of patients with SPs. We performed a careful search of the major medical and psychological databases by crossing SP with each neuroimaging technique. Functional neuroimaging, mostly using symptom provocation paradigms, showed abnormal activations in brain areas involved in emotional perception and early amplification, mainly the amygdala, anterior cingulate cortex, thalamus, and insula. The insula, thalamus and other limbic/paralimbic structures are particularly involved in SPs with prominent autonomic arousal. Emotional modulation is also impaired after exposure to phobic stimuli, with abnormal activations reported for the prefrontal, orbitofrontal and visual cortices. Other cortices and the cerebellum also appear to be involved in the pathophysiology of this disorder. Functional neuroimaging identified neural substrates that differentiate SPs from other anxiety disorders and separate SP subtypes from one another; the results support current Diagnostic and Statistical Manual of Mental Disorders, 4th edition-Text Revision (DSM-IV-TR) diagnostic subtyping of SPs. Functional neuroimaging shows promise as a means of identifying treatment-response predictors. Improvement in these techniques may help in clarifying the neurocircuitry underlying SP, for both research and clinical-therapeutic purposes.