Investigating neurophysiological effects of a short course of tDCS for cognition in schizophrenia: a target engagement study.

BackgroundCognitive impairment is highly prevalent in schizophrenia and treatment options are severely limited. Development of effective treatments will rely on successful engagement of biological targets. There is growing evidence that the cognitive impairments in schizophrenia are related to impairments in prefrontal cortical inhibition and dysfunctional cortical oscillations. MethodsIn the current study we sought to investigate whether a short course of transcranial Direct Current Stimulation (tDCS) could modulate these pathophysiological targets. Thirty participants with schizophrenia were recruited and underwent neurobiological assessment (Transcranial Magnetic Stimulation combined with EEG [TMS-EEG] and task-related EEG) and assessment of cognitive functioning (n-back task and the MATRICS Consensus Cognitive Battery). Participants were then randomized to receive 5 sessions of either active or sham anodal tDCS to the left prefrontal cortex. Twenty-four hours after the last tDCS session participants repeated the neurobiological and cognitive assessments. Neurobiological outcome measures were TMS-evoked potentials (TEPs), TMS-related oscillations and oscillatory power during a 2-back task. Cognitive outcome measures were d prime and accurate reaction time on the 2-back and MATRICS scores. ResultsFollowing active tDCS there was a significant reduction in the N40 TEP amplitude in the left parietal occipital region. There were no other significant changes. ConclusionsFuture interrogation of evidence based therapeutic targets in large scale RCTs is required.