Investigating visual effects of a disgust nocebo with fMRI.

There is growing evidence that placebos are able to influence visual perception. A previous functional magnetic resonance imaging (fMRI) study on the processing of disgust images demonstrated that a 'disgust placebo' (inert pill administered with the verbal suggestion of an anti-nausea medication) reduced visual cortex activity and connectivity. In the present fMRI investigation, we examined corresponding visual effects of a 'disgust nocebo' (an odorless substance introduced as an aversive smell that enhances disgust feelings). We reanalyzed data from 29 women, who viewed disgusting, fear-eliciting, and neutral images once with and once without the nocebo. In the nocebo condition with disgusting images, experienced disgust significantly increased together with fusiform gyrus activation, which showed enhanced coupling with the amygdala, and several (extra)striate cortex regions. The nocebo changed the affective value and motivational relevance of the stimuli as well the perception of basic visual features. These findings demonstrate that nocebo-related expectations can have a strong influence on the experience of sensory input.