Amelioration of cognitive control in depression by transcranial direct current stimulation

Deficient cognitive control over emotional distraction is a central characteristic of major depressive disorder (MDD). Hypoactivation of the dorsolateral prefrontal cortex (dlPFC) has been linked with this deficit. In this study, we aimed to enhance the activity of the dlPFC in MDD patients by anodal transcranial direct current stimulation (tDCS) and thus ameliorate cognitive control.

In a double-blinded, balanced, randomized, sham-controlled crossover trial, we determined the effect of a single-session tDCS to the left dlPFC on the cognitive control in 22 MDD patients and 22 healthy control subjects. To assess the cognitive control, we used a delayed response working memory task with pictures of varying content (emotional vs. neutral) presented during the delay period.

Emotional pictures presented during the delay period impaired accuracy and response time of patients with MDD, indicating an attentional bias for emotional stimuli. Anodal tDCS to the dlPFC was associated with an enhanced working memory performance both in patients and control subjects. Specifically in subjects with MDD, the attentional bias was completely abolished by anodal tDCS.

The present study demonstrates that anodal tDCS applied to the left dlPFC improves deficient cognitive control in MDD. Based on these data, tDCS might be suitable to support the effects of behavioral training to enhance cognitive control in MDD.