O9.2. EFFECTS OF ANODAL TDCS ON SPATIAL WORKING MEMORY IN PATIENTS WITH SCHIZOPHRENIA. (9th April 2019)

• Record Type: Journal Article
• Authors: Schwippel, Tobias; Plewnia, Christian
• Is Part Of: Schizophrenia bulletin. Volume 45(2019)Supplement 2
• Page Start: S187
• Page End: S187
• Publication Date: 2019-04-09
• Subjects: Schizophrenia -- Periodicals; Schizophrenia -- Research -- Periodicals; 616.898005
• DOI: 10.1093/schbul/sbz021.242
• Languages: English
• ISSNs: 0586-7614

Abstract

Abstract: Background: Neurocognitive impairment is a core, severely disabling feature of schizophrenia and predicts functional outcomes, including life satisfaction and the ability to return to work. Impaired working memory is frequently observed and is consistently associated with reduced activation of the dorsolateral prefrontal cortex (DLPFC). Pharmacological therapy is not effective and cognitive remediation therapy shows only a mild to moderate effect on cognitive functions. Non-invasive brain stimulation can enhance executive functions in healthy subjects and first studies suggest effects in patients as well. Together with other influencing factors the optimal stimulation parameters have to be explored to verify the clinical use of tDCS for patients with schizophrenia. In the future, individualized stimulation paradigms might contribute to rehabilitation efforts in order to enable patients to live a self-determined life. Methods: 32 patients with the DSM-5 diagnosis of schizophrenia were enrolled in this double-blind, sham controlled cross-over study. The first experiment was conducted with 1 mA and the second with 2 mA current strength. Both otherwise identical experiments consisted of three experimental sessions, in which a spatial n-back task was administered. The anode was placed over the right dorsolateral prefrontal cortex and the cathode over the contralateral deltoid muscle. Calculated baseline adjusted d-prime was defined as primary outcome, while reaction time served as secondary outcome. Results: In experiment 1 (1 mA), no difference between sham and anodal stimulation was found for working memory performance or reaction time. However, the use of 2 mA did result in a significant improvement of working memory performance by tDCS. This enhancement was specifically observed during a task with high cognitive load (3-back) and was accompanied by a slowing of reaction time during anodal stimulation. These results are in line with the notion, that higher current intensities are necessary to elicit behavioral effects in neuropsychiatric patients and highlight the task dependency of tDCS effectiveness Discussion: The key finding of this study is that 2 mA anodal tDCS to the right dlPFC can improve n-back performance in patients with schizophrenia. The significant improvement was detected in the task with the highest memory load (3-back). This beneficial effect was negatively correlated with measures of general cognitive ability. Remarkably, a significant slowing of response time was observed with 2 mA anodal tDCS pointing towards a shift in the speed-accuracy tradeoff in favor of accuracy. No effect of 1 mA tDCS on WM performance or response time was found, indicating the necessity of higher current intensities to elicit behavioral effects in patients with schizophrenia.