The Effects of tDCS on Auditory Hallucination, Insight, Neurocognitive Function and HRV in Patients With Schizophrenia

Transcranial direct current stimulation (tDCS), a novel, non-invasive and safe neuro-modulating technique, has been developed as a new therapeutic option for neuropsychiatric disorders. It encompasses the induction of a relatively weak constant current flow through the cerebral cortex via scalp electrodes. Dependent on stimulation polarity, this results in a modulation of cortical excitability and spontaneous neural activity. The technique was established in the 1950s and 1960s primarily in animals. In these early studies it was shown that subthreshold DC stimulation increases spontaneous neuronal activity if the anode is placed above or within the cortex, while exposure to cathodal polarity results in reduced activity. This is caused by a subthreshold membrane depolarization by anodal and a hyperpolarization by cathodal stimulation. It was demonstrated in humans that the after-effects of tDCS depend on modifications of NMDA receptor-efficacy. The after-effects of tDCS are blocked by the NMDA receptor antagonist dextromethorphan, and prolonged by the partial NMDA receptor-agonist D-cycloserine. This tDCS polarity-dependent alteration of NMDA receptor function seems to be initiated by the respective membrane potential shift and probably by the accompanying cortical activity modification,because it is prevented by the sodium channel blocker carbamazepine. Intraneuronal calcium concentration also contributes, because calcium channel antagonists eliminate the excitability-enhancing aftereffects of anodal tDCS. Recently, tDCS has been found to improve psychopathological symptoms (auditory hallucination in particular), cognitive deficits and insight of schizophrenia and also strengthen cardiac autonomic function in healthy subjects. Further replication studies are needed. The study aimed to investigate whether transcranial direct current stimulation could modify auditory hallucination, insight, neurocognitive function, heart rate variability, psychosocial functioning and quality of life in patients with schizophrenia. Study design: randomized double-blind, sham-controlled study design. Participants: 60 patients having a diagnosis of schizophrenia or schizoaffective with refractory auditory verbal hallucinations (defined as the persistence of daily auditory verbal hallucinations without remission in spite of antipsychotic medications at an adequate dosage for at least 3 months), aged 20-65 years. Others: see Arms and Interventions, Eligibility Criteria or Outcome Measures.