An investigation into the effects of tDCS dose on cognitive performance over time in patients with schizophrenia

Cognitive deficits in schizophrenia underlie more functional disability than any other symptom of the illness and existing treatments are largely inadequate. Non-invasive brain stimulation has been shown to enhance aspects of cognition in both healthy controls and patient populations; however there has been very little research into the use of tDCS for enhancing cognitive performance in schizophrenia. We conducted an initial investigation into the post stimulation effects of tDCS on cognitive performance in a repeated measures design in 18 patients with schizophrenia; in particular looking at dose of stimulation. Specifically, we provided a single 20-minute session of anodal left dorsolateral prefrontal tDCS (1 mA, 2 mA, sham) and measured performance on a working memory task across three time points post-stimulation (0, 20 and 40 min). Our results revealed a significant improvement in performance over time following 2 mA stimulation only. These findings speak to the feasibility of tDCS for enhancing cognitive performance in schizophrenia, as well as the importance of dose of stimulation.