P 42. Modulation of healthy and disturbed cognitive control with transcranial direct current stimulation

Abstract

Introduction Cognitive control (CC) is of decisive relevance for adaptive human behavior. Deficient CC is a central characteristic of major depressive disorder (MDD). Insufficient activation of the dorsolateral prefrontal cortex (dlPFC) has been linked with this deficit. The activity of distinctive brain areas can be transiently modulated by transcranial direct current stimulation (tDCS). Objectives First, to explore the role of the dlPFC in CC and its disturbance in MDD by means of tDCS. Second, to evaluate the feasibility of polarity-specific, selective modulation of CC with tDCS. Third, to investigate the potential of anodal tDCS to ameliorate disturbed CC in MDD. Materials and methods CC was assessed by emotional distractibility in a delayed working memory task (DWM) and an attentional bias task (ABT). In a randomized cross-over design, activity enhancing anodal tDCS or sham stimulaiton was applied to the left dlPFC (1 mA, 20 min, cathode at right upper arm) during DWM performance enhanced working memory in healthy subjects ( n = 22) and MDD patients ( n = 22). In turn, inhibiting, cathodal tDCS was to the left dlPFC (1 mA, 20 min, anode at right upper arm) was compared to sham stimulation in healthy subjects ( n = 28). Results We found that activity enhancing anodal tDCS to the left dlPFC during DWM performance enhanced working memory in healthy subjects and MDD patients. Most importantly, it ameliorated emotional distraction prevalent in patients with MDD. Reciprocally, inhibiting, cathodal tDCS impairs CC on the influence of negative stimuli in healthy subjects reflected by a decrease of correct responses in the DWM and an increase in reaction time in the following ABT. Conclusion These findings demonstrate a tDCS-polarity specific plasticity of CC and thus verify the important role of left dlPFC activity for this key feature of human cognition and its disturbance in MDD. Therefore our data point towards new opportunities for the treatment of MDD by a specific combination of brain stimulation techniques and cognitive-behavioral treatment strategies.