FUNCTIONAL NEUROANATOMY OF VISUALLY ELICITED SIMPLE PHOBIC FEAR - ADDITIONAL DATA AND THEORETICAL-ANALYSIS

We investigated central nervous system correlates of simple phobic fea r. Regional cerebral blood flow (rCBF) was measured using positron emi ssion tomography (PET) in eight volunteers with symptomatic spider pho bia that were exposed to visual phobogenic and neutral stimuli. Diazep am (0.1 mg/kg body weight i.v.) or placebo was administered under doub le-blind conditions after initial PET scans. The PET scans were then r epeated. The presence of fear was confirmed by rating procedures and i ncreased number of nonspecific electrodermal fluctuations and by highe r heart rate during phobic than during neutral stimulation. Phobic as compared to neutral stimulation elevated the regional to whole brain ( relative) CBF in the secondary visual cortex but reduced relative rCBF in the hippocampus, prefrontal, orbitofrontal, temporopolar, and post erior cingulate cortex. Diazepam treatment did not affect the relative rCBF or the subjective or physiological fear indices. The observed rC BF pattern replicates our previous findings in snake phobics (M. Fredr ikson et al. [1993] Psychophysiology, 30, 127-131; G. Wik et al. [1993 ] Psychiatry Research (Neuroimaging), 50, 15-24) and indicates that fe ar and anxiety affect cortical areas outside the classic limbic system areas.