Background
The amygdala has been strongly implicated in the processing of threat-relevant information
in specific phobia. However, there is an ongoing debate as to whether the amygdala
may also be engaged outside of conscious stimulus awareness. Furthermore, considering
that sustained vigilance for threat constitutes a crucial characteristic of specific
phobias, we hypothesized a possible role of this symptom in modulating amygdala sensitivity
to disorder-relevant cues. Using event-related functional magnetic resonance imaging,
we examined responses of the amygdala to subliminal and supraliminal phobogenic stimuli
in spider-phobic subjects and whether these responses might be specifically associated
with disorder-related hypervigilance.
Methods
Eighteen female spider-phobic subjects and 18 healthy female control subjects were
exposed to pictures of spiders and phobia-irrelevant objects, presented briefly during
two backward-masking conditions used to manipulate stimulus awareness. Brain activation
data were analyzed as a function of subjects' perceptual performance on each single
trial and were tested for correlations with different components of the phobic symptomatology,
such as vigilance, as assessed by self-report scales.
Results
Compared with control subjects, phobic participants showed stronger responses of both
amygdalae to consciously perceived spiders versus nonspider targets, whereas during
unconscious stimulus processing, enhanced activation was only apparent in the right
amygdala. Moreover, the intensity of disorder-related vigilance was positively correlated
with right amygdala activation specifically during the subliminal condition.
Conclusions
These findings provide evidence for unconscious threat processing in specific phobia,
with the magnitude of amygdala responses specifically potentiated by sustained hypervigilance
for threat. Aberrations in this vigilance system may be critically involved in anxiety
disorders.
Key Words
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Article info
Publication history
Published online: May 25, 2011
Accepted:
April 6,
2011
Received in revised form:
March 22,
2011
Received:
October 5,
2010
Identification
Copyright
© 2011 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
