The effects of transcranial electrical stimulation (tES) on interference control: A systematic review of stimulation effects

Interference control has received a lot of attention throughout the centuries and has been studied extensively in recent years with regards to how it can be modulated by transcranial electrical stimulation. Interference control, which refers to the ability to resist conflicting information, is most commonly assessed with the Stroop task, the Flanker task and the Simon task, which induce differences in response times and accuracy rates between congruent and incongruent trials. There has been an emerging body of literature suggesting that stimulating specific brain regions with electrical currents is able to alter conflict-reducing processes. However, results have been widely heterogeneous, with some studies finding enhancement of related cognitive functions and others finding no reliable effects. Therefore, this systematic review aims to investigate whether different methods of transcranial electrical stimulation (tES) reliably modulate interference control. The findings are mixed and proof that a reliable alteration of interference control is not possible. Most promising for a successful performance modulation seem to be the stimulation of the anterior cingulate cortex (especially with tACS in the theta frequency) and the implementation of a Stroop task. Thus, although there are indications for favorable neurostimulation and methodological designs, the majority of results is inconsistent and hence, the reliability of the results open to question.