Neural correlates of emotional processing in idiopathic environmental intolerance : an fmri study

Abstract: Idiopathic environmental intolerance (IEI) is still medically unexplained. Conditioning and sensitization have been proposed to contribute to the symptoms. No study to date has used functional magnetic resonance imaging (fMRI) to study brain activation in IEI. The objective of the present study was to investigate whether individuals with IEI during chemosensory exposure activate brain circuitries associated with negative emotional processing and to examine if they sensitize to chemosensory stimuli. Brain activation was studied with fMRI in 26 female subjects with IEI and 30 age- and gender-matched healthy controls during exposure to olfactory and chemosomatosensory stimuli. Stimuli were presented in a blocked design with intensity ratings during each block. Subjects with IEI showed increased activation in amygdala, insula, dorsal anterior cingulate cortex and dorsal prefrontal cortex during exposure to carbon dioxide. In addition, they showed decreased activation in medial refrontal cortex. These results imply negative emotional processing in IEI that is similar to what is seen in anxiety disorders. Further, specific phobia is proposed as a model for the understanding of how IEI develops and is maintained. The findings might have implications for the treatment of IEI.