Enhancing cognitive control training with transcranial direct current stimulation: a systematic parameter study

Abstract

Background: Cognitive control (CC) is an important prerequisite for goal-directed behaviour and efficient information processing. Impaired CC is associated with reduced prefrontal cortex activity and various mental disorders, but may be effectively tackled by transcranial direct current stimulation (tDCS)-enhanced training. However, study data are inconsistent as efficacy depends on stimulation parameters whose implementations vary widely between studies.

Objective: We systematically tested various tDCS parameter effects (anodal/cathodal polarity, 1/2 mA stimulation intensity, left/right prefrontal cortex hemisphere) on a six-session CC training combined with tDCS.

Methods: Nine groups of healthy humans (male/female) received either anodal/cathodal tDCS of 1/2 mA over the left/right PFC or sham stimulation, simultaneously with a CC training (modified adaptive Paced Auditory Serial Addition Task [PASAT]). Subjects trained thrice per week (19 min each) for two weeks. We assessed performance progress in the PASAT before, during, and after training. Using a hierarchical approach, we incrementally narrowed down on optimal stimulation parameters supporting CC. Long-term CC effects as well as transfer effects in a flanker task were assessed after the training period as well as three months later.

Results: Compared to sham stimulation, anodal but not cathodal tDCS improved performance gains. This was only valid for 1 mA stimulation intensity and particularly detected when applied to the left PFC.

Conclusions: Our results confirm beneficial, non-linear effects of anodal tDCS on cognitive training in a large sample of healthy subjects. The data consolidate the basis for further development of functionally targeted tDCS, supporting cognitive control training in mental disorders and guiding further development of clinical interventions.

Trial registration: ClinicalTrials.gov NCT04108663.

Keywords: Brain stimulation; Cognitive control; Cognitive enhancement; Neuropsychiatry; Prefrontal cortex; Transcranial direct current stimulation.

Conflict of interest statement

Declaration of competing interest SW and CP declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. MAN is scientific advisor for Neuroelectrics, and NeuroDevice.

Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.