Analgesic Effect of Non Invasive Stimulation : Transcranial Direct Current Stimulation of Opercular-insular Cortex

The aim of this study is to evaluate, versus placebo, the analgesic efficacy of the opercular-insular cortex stimulation with Transcranial Direct Current Stimulation (tDCS), in both healthy subjects and chronic neuropathic pain patients. In healthy subjects analgesia by tDCS will be assessed using both laser stimuli and cold pressor test. In patients the assessment regards their chronic pain (ratings for ongoing, evoked and paroxysmal pain, sleep and fatigue). Opercular-insular stimulation is obtained via a combined 6-electrode montage and by bi-vestibular stimulation (since vestibular pathways reach the posterior insular cortex). In patients, three separate conditions (two active and one sham) will be tested in randomised order. In healthy subjects, two other conditions are added to control for attention and distraction confounders.