The neuromodulatory effect of tDCS in patients affected by functional motor symptoms: an exploratory study

Background: Recent studies have shown how emotional and cognitive factors might combine together to determine the onset and maintenance of functional motor symptoms (FMS). Nevertheless, no studies have assessed whether brain circuits involved in regulation and processing of emotions and attention might be influenced by neuromodulation. The purpose of this study was to evaluate the effect of a single anodic tDCS session over the right posterior parietal cortex in subjects with FMS and in healthy individuals. Materials and methods: Nine patients and seven healthy subjects underwent two sessions of tDCS (real and sham), in a randomized order. At the end of each session, all participants underwent the heart beat detection task (interoceptive sensitivity) and the Posner paradigm (spatial attention). Results: After sham stimulation, patients with FMS showed significantly lower interoceptive sensitivity and greater cueing effect for reaction times at the Posner paradigm than healthy controls. There was a significant improvement between the levels of interoceptive sensitivity after real and sham stimulation in the whole group of participants and in the group of patients with FMS. Conclusions: Our study provides first indications for a neuromodulatory effect of a single anodic tDCS session over the right posterior parietal cortex on interoceptive sensitivity in subjects with FMS.