Fear Is Fast in Phobic Individuals: Amygdala Activation in Response to Fear-Relevant Stimuli

doi:10.1016/j.biopsych.2006.03.079

Biological Psychiatry

Volume 60, Issue 4, 15 August 2006, Pages 410-417

https://doi.org/10.1016/j.biopsych.2006.03.079 Get rights and content

Background

Two core characteristics of pathologic fear are its rapid onset and resistance to cognitive regulation. We hypothesized that activation of the amygdala early in the presentation of fear-relevant visual stimuli would distinguish phobics from nonphobics.

Methods

Chronometry of amygdala activation to phobia-relevant pictures was assessed in 13 spider phobics and 14 nonphobics using functional magnetic resonance imaging (fMRI).

Results

Blood oxygen level-dependent (BOLD) responses in the amygdala early in picture processing consistently differentiated between phobic and nonphobic subjects, as well as between phobogenic and nonphobogenic stimuli among phobics. Furthermore, amygdalar BOLD responses associated with timing but not magnitude of activation predicted affective responses to phobogenic stimuli. Computational modeling procedures were used to identify patterns of neural activation in the amygdala that could yield the observed BOLD data. These data suggest that phobic responses were characterized by strong but brief amygdala responses, whereas nonphobic responses were weaker and more sustained.

Conclusions

Results are discussed in the context of the amygdala’s role in rapid threat detection and the vigilance-avoidance hypothesis of anxiety. These data highlight the importance of examining the neural substrates of the immediate impact of phobogenic stimuli for understanding pathological fear.

Section snippets

Participants

Participants were female undergraduates who participated in a mass screening for course credit. Women scoring greater than 20 (94th percentile in the current sample) on the Spider Phobia Questionnaire (Klorman et al 1974) were classified as phobics, and women scoring 0 or 1 were classified as nonphobic. From this pool, thirty right-handed women (15 phobic and 15 control subjects) screened with the Structured Clinical Interview for DSM-IV Axis I Disorders (First et al 1995) met criteria for

Group × Condition Comparisons: Gamma Variate Data

To demonstrate the raw time series and gamma variate fit for the main condition of interest, the spider pictures, these waveforms for the left amygdala are presented in Figure 1. Intraclass correlations demonstrated a good fit between the raw and fitted time series for both control (intraclass correlation [ICC] = .98, p < .001; confidence interval [CI] = .97–.99) and phobic subjects (ICC = .99, p < .001; CI = .98–.99).

Discussion

These data suggest that amygdala activation in the very early stages of stimulus processing distinguish phobic from nonphobic responses. Faster time to onset and time to peak of amygdala BOLD responses to spiders consistently discriminated between groups and conditions. Model-fitting procedures demonstrated that these data could reflect a strong but brief activation among the phobic subjects and weaker but more sustained activation among the nonphobic subjects. Although the observed data could,

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Original articleFear Is Fast in Phobic Individuals: Amygdala Activation in Response to Fear-Relevant Stimuli

Background

Methods

Results

Conclusions

Section snippets

Participants

Group × Condition Comparisons: Gamma Variate Data

Discussion

Vision Res

Neuron

Neuron

Neuroimage

Psychiatry Res

Comput Biomed Res

Biol Psychol

Neurosci Letters

Neuron

Biol Psychiatry

Behavior Therapy

Neuron

Neuropsychologia

J Neurosci Meth

Behav Res Ther

Neurosci Biobehav Rev

Neuroimage

Behav Res Ther

Neuroimage

J Anxiety Disord

Neuron

Neuron

Biol Psychiatry

Biol Psychiatry

Neuron

Anatomical organization of the primate amygdaloid complex

Automatic activation and strategic avoidance of threat-relevant information in social phobia

J Abnorm Psychol

Cognitive biases in social phobia

The pupillary system

State anxiety modulation of the amygdala response to unattended threat-related stimuli

J Neurosci

Pictures as prepulseAttention and emotion in startle modification

Psychophysiology

Fear and the amygdalamanipulation of awareness generates different cerebral responses to phobic and fear-relevant (but nonfeared) stimuli

Emotion

The amygdalaVigilance and emotion

Mol Psychiatry

Organization of projections to the lateral amygdala from auditory and visual areas of the thalamus in the rat

J Comp Neurol

Original article
Fear Is Fast in Phobic Individuals: Amygdala Activation in Response to Fear-Relevant Stimuli