Lasting amelioration of deficient cognitive control by transcranial direct current stimulation (tDCS)-enhanced training

Principal Investigators: Christian Plewnia (Tübingen); Andreas Fallgatter (Tübingen)

 

Background and aims


Deficient cognitive control (CC) is one of the central characteristics of major depression (MD).1 Hypoactivation of the dorsolateral prefrontal cortex (dlPFC) has been linked with this deficit.2 Antidepressants and cognitive-behavioral therapies modify CC most-likely as a common mechanism of treatment.3 We have shown, that activity of 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.4 This effect is modulated by task proficiency4 and genetic variations.5 Particularly, we demonstrated that enhancement of left dlPFC activity by anodal tDCS can transiently ameliorate CC in MD.6 In turn, cathodal, deactivating tDCS to the same area induces a negativity bias in healthy subjects.7 Therefore, tDCS can modulate healthy and disturbed CC in a polarity dependent manner and the combination of tDCS and cognitive training might be effective in augmenting benefits of cognitive therapies. However, the optimal stimulation conditions for a tDCS-enhanced cognitive training are still unknown. Therefore, we first compare the effects of anodal and cathodal tDCS to the left and right dlPFC at 1 and 2 mA with sham stimulation in healthy subjects during training of CC with the ‘Paced Auditory Serial Addition Task’ (PASAT).8 This tDCS-enhanced training will be practiced at 6 sessions in 2 weeks. Sustainability and generalization of the training effects will be measured at follow-up visits (1 weeks, 3 months). The most effective parameters will be used to assess the effects of tDCS-enhanced training on CC and clinical improvement in patients with major depression. Concurrently, we will analyze the neurophysiological mechanisms, genetic factors and the effect of gender on the tDCS-enhanced training effects. These experiments will provide essential data for an evidence-based combination of brain stimulation with cognitive training as a potentially valuable new constituent of cognitive-behavioural therapy.

 

Working hypothesis


Healthy and impaired cognitive control capacity can be enhanced by combining transcranial direct current stimulation (tDCS) with cognitive training.

 

Research questions


  1. This series of experiments will collect evidence for the malleability of cognitive control on emotional information processing by tDCS-enhanced cognitive training and its optimal parameters and conditions,
  2. the efficacy of this intervention on impaired cognitive control in patients with depression
  3. and the neurophysiological, genetic and gender-specific modulators of this effect.