ABSTRACT
Transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation, is a promising treatment for depression. Recent research suggests that tDCS efficacy can be augmented using concurrent cognitive emotional training (CET). However, the neurophysiological changes associated with this combined intervention remain to be elucidated. We therefore examined the effects of tDCS combined with CET using electroencephalography (EEG). A total of 20 participants with treatment resistant depression took part in this open-label study and received 18 sessions over 6 weeks of tDCS and concurrent CET. Resting-state and task-related EEG during a 3-back working memory task were aquired at baseline and immediately following the treatment course. Results showed an improvement in mood and working memory accuracy, but not response time, following the intervention. We did not find significant effects of the intervention on resting-state power spectral density (frontal theta and alpha asymmetry), time-frequency power (alpha event-related desynchronization and theta event-related synchronisation), or event-related potentials (P2 and P3 components). We therefore identified little evidence of neurophysiological changes associated with treatment using tDCS and concurrent CET, despite significant improvements in mood and near transfer effects of cognitive training to working memory accuracy. Further research incorporating a sham controlled group may be necessary to identify the neurophysiological effects of the intervention.
Footnotes
The manuscript has been amended clarify that this work is intended to focus on neurophysiological changes associated with tDCS combined with cognitive emotional therapy. Clinical efficacy of this intervention was discussed in a previous paper from our group (Martin et al., 2018), which was based on a partly overlapping sample to the one used in the current study. Additionally, we incorporated non-parametric analysis for some EEG outcomes, as they were not normally distributed, as well as for supplementary correlation analyses.
We added reporting on adverse event outcomes to allow for comparison with other studies delivering multiple sessions of tDCS.
