Investigating visual effects of a disgust nocebo with fMRI

Abstract

There is growing evidence that placebos are able to influence visual perception. A previous functional magnetic resonance imaging 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 functional magnetic resonance imaging investigation, visual effects corresponding to a “disgust nocebo” (an odorless substance introduced as an aversive smell that enhances disgust feelings) were examined. Data from 29 females were reanalyzed. They viewed disgusting, fear-eliciting, and neutral images once with and once without the nocebo. In the nocebo condition with disgusting images disgust experienced that significantly increased fusiform gyrus activation, which also 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.

Keywords

• |placebo|nocebo|disgust|visual cortex|functional magnetic resonance imaging|psychophysiological interaction analysis