Mechanistic Clinical Trial of Individualized tDCS for Hallucinations in Schizophrenia

The large majority of patients with schizophrenia (Sz) experience auditory verbal hallucinations (AVH) as a core feature of their disorder. Treatment-resistant auditory verbal hallucinations (AVH) affect a third of patients with schizophrenia and can cause increased aggression, distress, suicide, and social dysfunction. This project will investigate the efficacy of different types of transcranial direct current stimulation (tDCS), a neurostimulation technique that passes a weak electric current through the brain, in alleviating AVH in Sz patients, and will explore hypotheses regarding brain circuits involved in AVH. This project compares standard tDCS to individualized high-definition tDCS (HD-tDCS) for treatment of AVH. In standard tDCS, two large electrodes are positioned on the scalp above regions of the brain implicated in abnormal cortical activity associated with auditory verbal hallucinations in Sz. Due to the size of standard tDCS electrodes and the positions required to stimulate language areas, large unrelated areas of the brain are also stimulated. HD-tDCS is a novel technique that uses multiple smaller electrodes to produce a more focal electrical field (EF) than standard tDCS. The HD-tDCS used in this study modulates brain activity in a targeted area without stimulating as many unrelated areas. This targeted inhibition allows us to test hypotheses regarding different cortical regions and their roles in specific features of AVH (e.g. loudness and salience). Participants are randomized to receive either active standard tDCS or active HD-tDCS targeting one of two language-processing areas of the brain, or a sham version of one of these stimulation types. For each participant receiving HD-tDCS, structural MRI is used to computationally model the electrical field produced in their individual brain anatomy by tDCS. These models are then used to select individualized electrode configurations and current settings to target the same language areas across subjects. The effect of stimulation on relevant brain functions is verified by measuring pre/post treatment changes in resting state functional connectivity (rsFC) within and between targeted language regions, which has been previously linked to AVH symptoms. Differences in behavioral task performance and neurophysiological abnormalities associated with AVH are also tested pre/post treatment.