Neuronal correlates of symptom formation in functional somatic syndromes: a fMRI study

Functional somatic syndromes are characterized by high morbidity due to various, fluctuating symptoms without objective somatic findings. There is increasing evidence for the contribution of emotional and cognitive functions to symptom formation, which has been well established in the perception of pain. In addition to their involvement in various other cognitive and emotional processes, the anterior cingulate and insular cortex are thought to contribute to the so-called "pain neuromatrix". Recent data suggest that these areas appear also to be involved in symptom manifestation in multiple chemical sensitivity. Here we used functional Magnetic Resonance Imaging (fMRI) to test whether this network is also involved in the induction of unpleasant perceptions by sham mobile phone radiation in subjectively electrosensitive patients. This design enabled us to completely dissociate the unpleasant subjective perception from any real physical stimulus. Fifteen subjectively electrosensitive patients and 15 age- and gender-matched healthy controls were exposed to sham mobile phone radiation and heat as a control condition. The perceived stimulus intensities were rated on a five-point scale. During anticipation of and exposure to sham mobile phone radiation increased activations in anterior cingulate and insular cortex as well as fusiform gyrus were seen in the electrosensitive group compared to controls, while heat stimulation led to similar activations in both groups. Symptom manifestation during sham exposure to mobile phone radiation was accompanied by specific alterations of cortical activity in anterior cingulate and insular cortex in subjectively electrosensitive patients further supporting the involvement of these areas in the perception of unpleasantness and generation of functional somatic syndromes.