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The present fMRI study investigated whether placebo treatment can change disgust feelings. Disgust-prone women underwent a retest design where they were presented with disgusting, fear-eliciting and neutral pictures once with and once without a placebo (inert pill presented with the suggestion that it can reduce disgust symptoms). The placebo provoked a strong decrease of experienced disgust, which was accompanied by reduced insula activation. Exploratory psychophysiological interaction analyses revealed decreased connectivity in a network consisting of the insula, the amygdala, the anterior cingulate cortex and the orbitofrontal cortex. Moreover, the placebo increased amygdala-DMPFC coactivation. Our findings suggest that placebo use can modulate a specific affective state and might be an option as a first therapy step for clinical samples characterized by excessive and difficult-to-control disgust feelings.

This symptom provocation study on spider phobia investigated sources of late event-related potentials (ERPs) using sLORETA (standardized low resolution brain electromagnetic tomography). Twenty-five phobic female patients and 20 non-phobic controls were confronted with phobia-relevant, generally fear-inducing, disgust-inducing and affectively neutral pictures while an electroencephalogram was recorded. Mean amplitudes of ERPs were extracted in the time windows 340–500 ms (P300) and 550–770 ms (late positive potential, LPP). Phobics showed enhanced P300 and LPP amplitudes in response to spider pictures relative to controls. Sources were mainly located in areas engaged in visuo-attentional processing (occipital and parietal regions, ventral visual pathway). Moreover, there were sources in areas which are crucial for emotional processing and the representations of aversive bodily states (cingulate cortex, insula). Further sources were located in premotor areas reflecting the priming of flight behaviour. Our findings are in good accordance with existing brain imaging studies and underline that source localization is a useful alternative for identifying phobia-relevant cortical regions.

Although dental phobia is a common mental disorder, which afflicts both men and women, little is known about sex differences at the neural level. Patients suffering from dental phobia (20 men, 25 women) and healthy controls (18 men, 23 women) participated in a functional magnetic resonance imaging (fMRI) experiment. They were shown pictures depicting dental treatment, generally fear-eliciting, disgust-eliciting and neutral contents. After the fMRI experiment, the participants rated the affective value of the pictures. Additionally, grey matter volume (GMV) was compared between patients and controls, as well as between the sexes. Male and female patients responded differently to the phobogenic pictures. Women showed greater activation of the caudate nucleus, whereas men exhibited enhanced dorsolateral prefrontal cortex (DLPFC) involvement. Their DLPFC activation was negatively correlated with experienced arousal. Dentophobic females were characterized by a greater caudate volume relative to phobic males. The GMV of this structure was positively correlated with experienced arousal during exposure and symptom severity, only in female patients. This study provides first evidence of sex-specific brain activation and structure in patients suffering from dental phobia. The neural pattern during symptom provocation as well as the brain structural specificity might mirror different attention and self-control strategies of both sexes. The consideration of such differences could contribute to greater effectiveness in treating dental phobia.

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