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  • Theories of specific phobias consider classical conditioning as a central mechanism in the pathogenesis and maintenance of the disorder. Although the neuronal network underlying human fear conditioning is understood in considerable detail, no study to date has examined the neuronal correlates of fear conditioning directly in patients with specific phobias. Using functional magnet resonance imaging (fMRI) we investigated conditioned responses using phobia-relevant and non-phobia-relevant unconditioned stimuli in patients with specific phobias (n=15) and healthy controls (n=14) by means of a differential picture-picture conditioning paradigm: three neutral geometric figures (conditioned stimuli) were followed by either pictures of spiders, highly aversive scenes or household items (unconditioned stimuli), respectively. Enhanced activations within the fear network (medial prefrontal cortex, anterior cingulate cortex, amygdala, insula and thalamus) were observed in response to the phobia-related conditioned stimulus. Further, spider phobic subjects displayed higher amygdala activation in response to the phobia-related conditioned stimulus than to the non-phobia-related conditioned stimulus. Moreover, no differences between patients and healthy controls emerged regarding the non-phobia-related conditioned stimulus. The results imply that learned phobic fear is based on exaggerated responses in structures belonging to the fear network and emphasize the importance of the amygdala in the processing of phobic fear. Further, altered responding of the fear network in patients was only observed in response to the phobia-related conditioned stimulus but not to the non-phobia-related conditioned stimulus indicating no differences in general conditionability between patients with specific phobias and healthy controls.

  • Although it is known that there are fundamental personality differences in the behavioral responses to emotional stimuli, traits have scarcely been investigated in this context by means of functional imaging studies. To maximize the variance with respect to personality, the authors tested 12 control subjects and 12 subjects who had sadomasochistic experiences with respect to the relationship between J. A. Gray's (1970) personality dimensions, the behavioral approach system (BAS) and the behavioral inhibition system (BIS), and brain activity in regions of interest. The BIS was associated with activity in numerous brain areas in response to fear, disgust, and erotic visual stimuli, whereas few associations could he detected between the BAS and brain activity in response to disgust and erotic stimuli.

  • fMRI studies have shown that the perception of facial disgust expressions specifically activates the insula. The present fMRI study investigated whether this structure is also involved in the processing of visual stimuli depicting non-mimic disgust elicitors compared to fear-inducing and neutral scenes. Twelve female subjects were scanned while viewing alternating blocks of 40 disgust-inducing, 40 fear-inducing and 40 affectively neutral pictures, shown for 1.5 s each. Afterwards, affective ratings were assessed. The disgust pictures, rated as highly repulsive, induced activation in the insula, the amygdala, the orbitofrontal and occipito-temporal cortex. Since during the fear condition the insula was also involved, our findings do not fit the idea of the insula as a specific disgust processor.

Last update from database: 04.06.25, 15:35 (UTC)