Functional neuroanatomy of visually elicited simple phobic fear: Additional data and theoretical analysis

Abstract

We investigated central nervous system correlates of simple phobic fear. Regional cerebral blood flow (rCBF) was measured using positron emission tomography (PET) in eight volunteers with symptomatic spider phobia that were exposed to visual phobogenic and neutral stimuli. Diazepam (0.1 mg/kg body weight i.v.) or placebo was administered under double-blind conditions after initial PET scans. The PET scans were then repeated. The presence of fear was confirmed by rating procedures and increased number of nonspecific electrodermal fluctuations and by higher 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 posterior cingulate cortex. Diazepam treatment did not affect the relative rCBF or the subjective or physiological fear indices. The observed rCBF pattern replicates our previous findings in snake phobics (M. Fredrikson et al. [1993] Psychophysiology, 30, 127-131; G. Wik et al. [1993] Psychiatry Research (Neuroimaging), 50, 15-24) and indicates that fear and anxiety affect cortical areas outside the classic limbic system areas.

Role of the Basolateral Nucleus of the Amygdala in the Formation of a Phobia

“…To establish possible therapies, it will be necessary to identify the brain regions crucial for the retrieval of the emotional information underlying a phobia and the neurotransmitter pathways and receptors involved. Recent positron emission tomography (PET) studies of snake (Fredrikson et al 1993) and spider phobics (Fredrikson et al 1995) confirm that the amygdala is not activated during the elicitation of a phobic response, but show increased activation of the secondary visual cortex and reduced activation of the hippocampus, prefrontal, and cingulate cortex. The PET studies also confirm that the phobic response and pattern of brain activation is not changed by diazepam (Fredrikson et al 1995).…”

“…Recent positron emission tomography (PET) studies of snake (Fredrikson et al 1993) and spider phobics (Fredrikson et al 1995) confirm that the amygdala is not activated during the elicitation of a phobic response, but show increased activation of the secondary visual cortex and reduced activation of the hippocampus, prefrontal, and cingulate cortex. The PET studies also confirm that the phobic response and pattern of brain activation is not changed by diazepam (Fredrikson et al 1995). These PET studies should provide a useful guide for future neuroanatomical and neuropharmacological studies using our animal model.…”

Effects of Cannabidiol (CBD) on Regional Cerebral Blood Flow

“…Increased activity in the posterior cingulate gyrus has been associated with watching anxiety-provoking videos (Fischer et al, 1996, Fredrikson et al, 1995a, and with experimentally provoked obsessions and anxiety in patients with obsessive-compulsive disorder (OCD) (McGuire et al, 1994). Untreated patients with OCD show increased metabolism in the posterior cingulate (Perani et al, 1995) that decreases with treatment, with the change in posterior cingulate rCBF correlated with symptomatic improvement (Rauch et al, , 2002.…”

Transtornos ansiosos na infância e adolescência: aspectos clínicos e neurobiológicos

“…However, results of neuroimaging studies still have not provided clear anatomical information on the pathophysiology of specific phobias. 43,47 Neuroimaging studies reinforce the neurobiological model of PTSD, which emphasizes the functional relationship between amygdala, prefrontal cortex and hippocampus. When exposed to memories of traumatic events, individuals with PTSD seem to activate anterior paralimbic regions.…”