Deficient cognitive control (CC) is one of the central characteristics of major depression
(MD). Hypoactivation of the dorsolateral prefrontal cortex (dlPFC) has been linked with this
deficit. Antidepressants and cognitive-behavioral therapies modify CC most-likely as a common
mechanism of treatment. Transcranial direct current stimulation (tDCS) is a safe, simple and
effective non-invasive method to modulate the cortical excitability. It has been shown, that
the activity of the dlPFC can be modulated by transcranial direct current stimulation (tDCS)
with polarity-dependent learning-phase specific effects on performance that, when combined
with training, can outlast the stimulation.
The goal of this randomized, sham-controlled, rater blind clinical trial is to investigate
the effect of a tDCS-enhanced CC Training (CCT) on depressive symptom severity and compare
the stimulation intensities 1mA, 2mA and sham tDCS. Overall, the study will include 57
participants (n = 19 per group). Each participant will complete 12 training sessions with
online sham/ anodal tDCS.
As a training task we will use an adaptive version of the paced auditory serial addition task
(PASAT). In the PASAT, digits are presented auditive and participants have to add the current
digit to the digit they heard before. In the adaptive version the interstimulus-intervals
decrease (increase) when four consecutive trials are correct (incorrect). The PASAT is known
to elicit frustration. Participants have to exert cognitive control over these emotions to
complete the task successfully.
Before, during and after the training symptom severity will be assessed. Baseline and
post-training performance in the PASAT and in a transfer task (delayed working memory task,
DWM) will be measured.
To further explore variables that influence the effect of tDCS on depressive symptom severity
we will measure brain activity (EEG, NIRS), heart rate, global functioning (GAF), emotion
regulation strategies, self-esteem, mood ratings and subjective performance ratings before
and after the training and collect genetic factors.
Sustainability of the training effects will be measured at a follow-up visit (3 months
later).