P111. Exploring the effects of transcranial direct current stimulation on cognitive control training

Abstract

Introduction The dorsolateral prefrontal cortex (dlPFC) is a brain structure responsible for working memory performance and cognitive control (CC). CC, critically underlying goal-directed behaviour, has been shown to be impaired in depression and to be associated with reduced activity of the dlPFC ( Fitzgerald and Laird, 2008 ). Transcranial direct current stimulation (tDCS) of this brain area can modify the neuronal response and therefore CC, and has already shown potential for CC malleability: both amelioration as well as impairment ( [Wolkenstein and Plewnia, 2013] , [Plewnia et al., 2015a] , [Plewnia et al., 2015b] ). Within this study series we systematically investigate the effects of tDCS on a CC training in healthy participants by varying stimulation parameters regarding intensity, polarity and laterality. Methods Over the course of 8 sessions within 4 weeks and a follow-up session 3 months later participants perform a modified adaptive paced auditory serial addition task (PASAT) during which they hear a series of single digit numbers and are instructed to add the most recent digit to the third to last digit (n + n − 2). Digit presentation speed is adapted to performance with the goal to challenge CC by inducing stress and frustration during the experiment. TDCS is applied for 19 min during each training session. The first two test groups receive stimulation of the left dlPFC with 1 and 2 mA respectively, the third and fourth group are treated likewise except for stimulation being shifted to the right dlPFC. Each group is furthermore divided into subjects receiving either anodal, cathodal or sham tDCS. Preliminary results and conclusion Within the first study group, subjects who received anodal stimulation (1 mA) to the left dlPFC showed significant performance gains during PASAT training compared to cathodal (1 mA) and sham stimulation, suggesting that improvement was aided by plasticity enhancement of CC induced by tDCS. Outlook Data for the remaining three groups (2 mA, left dlPFC; 1 and 2 mA, right dlPFC) is currently being gathered. Collection will be finished by the end of the year, ensuing final analysis of the comprehensive data set by the beginning of 2018.