M28. Effect of Transcranial Direct Current Stimulation on Neurocognition, Social Cognition, and EEG in Schizophrenia

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Background: Individuals with schizophrenia experience very high levels of disability and poor community outcome, resulting in a major public health concern. Over the last decades, the treatment of schizophrenia has shifted fundamentally from a focus on symptom reduction to a focus on recovery and improving aspects of functioning. In this study, we examined the effect of transcranial direct current stimulation (tDCS) on neurocognitive and social cognitive functions, as well as on brainwave activity, in individuals with schizophrenia. This procedure is noninvasive and results in increase or decrease of spontaneous neuronal firing in the brain. Unlike other noninvasive brain stimulation techniques, such as transcranial electrical stimulation or transcranial magnetic stimulation, tDCS does not induce neuronal firing by suprathreshold neuronal membrane depolarization, but rather modulates spontaneous neuronal network activity. Methods: Thirty-seven individuals with schizophrenia were administered 1 of 3 randomly assigned tDCS conditions per visit over the course of 3 visits, with approximately 1 week between each visit: anodal tDCS over left DLPFC (cathodal over right supraorbital), cathodal tDCS over left DLPFC (anodal over right supraorbital), and sham stimulation. The current intensity was set at 2 mA and was maintained for two 20-minute sessions, with a 1-hour break between the sessions. Neurocognitive functions were assessed using the MATRICS Consensus Cognitive Battery (MCCB). Social cognition was assessed using the Managing Emotions component of Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT), the Emotion Identification Test from Ekman Program, the Profile of Nonverbal Sensitivity (PONS), and The Awareness of Social Inference Test (TASIT). Finally, EEG measures included standardized auditory oddball ERP and face perception protocols. Assessments were conducted immediately following each session, in a counterbalanced order of administration. Results: Despite the reasonably well-powered design, no systematic effects were found across the neurocognitive and social cognitive domains, and no significant effects were detected on EEG measures. Except for mild local discomfort (eg, itching and burning sensations at the site of the electrode), no significant side effects were reported, and no early termination of the procedure were requested. Conclusion: Findings demonstrate the safety and ease of administration of this procedure in schizophrenia, but raise dose and laterality related issues. It appears that repeated tDCS administration may be necessary to attain a therapeutic effect on cognition in schizophrenia.