Considering the influence of stimulation parameters on the effect of conventional and high-definition transcranial direct current stimulation

Wing Ting To, John Hart, Dirk De Ridder, Sven Vanneste
2016 Expert Review of Medical Devices  
Recently, techniques to non-invasively modulate specific brain areas gained popularity in the form of transcranial direct current stimulation (tDCS) and high-definition transcranial direct current stimulation. These non-invasive techniques have already shown promising outcomes in various studies with healthy subjects as well as patient populations. Despite widespread dissemination of tDCS, there remain significant unknowns about the influence of a diverse number of tDCS parameters (e.g.
more » ... , size, position of electrodes & duration of stimulation) in inducing neurophysiological and behavioral effects. This article explores both techniques starting with the history of tDCS, to the differences between conventional tDCS and high-definition transcranial direct current stimulation, the underlying physiological mechanism, the (in)direct effects, the applications of tDCS with varying parameters, the efficacy, the safety issues and the opportunities for future research. ARTICLE HISTORY Key issues • Conventional tDCS and HD-tDCS are considered safe with minimum risks when used within safety guidelines and for short-term use. • HD-tDCS allows for more focal stimulation compared to conventional tDCS. • By varying controllable tDCS parameters, stimulation protocols can be customized to a certain extent to achieve the desired direction, strength, focality, and duration of effects on cortical activity and excitability. • The relationship between intensity and duration of stimulation and efficacy of tDCS is not linear under all conditions. • tDCS exerts direct regional effects as well as indirect network effects.
doi:10.1586/17434440.2016.1153968 pmid:26894636 fatcat:yxt64veo6jb7dhjjvyfceay3my