The Value of Transcranial Direct Current Stimulation in Improving Working Memory in Neurotypical and Special Populations

Abstract

Transcranial direct current stimulation, or tDCS, uses electrodes applied to the scalp to deliver weak electrical currents to underlying cortical neurons to excite or inhibit them (Berryhill, 2017). This neurostimulation technique is both affordable and safe, which makes it an intriguing method to boost cognitive ability, specifically working memory. Working memory is a neural function that is critical to daily human existence but declines with age and can be degraded by neurological disorders (Brunoni et al., 2013; Shiozawa et al., 2014; Jones et al., 2015; Moreno et al., 2015; Kofler et al., 2018). It is for this reason tDCS headsets are now being manufactured by companies for at-home use by the general public to increase cognitive abilities such as intelligence, focus, and memory (NeuroStim, Fischer Wallace, BrainDriver). However, tDCS has been found to produce variable effects in different test groups: while some individuals have benefited from tDCS, others do not respond to stimulation or even experience impairments (Berryhill et al., 2014). The purpose of this literature review is to assess the value of tDCS in improving working memory in neurotypical and special populations, such as older adults or clinical patients, based on empirical findings from studies within the past three years. A systematic evaluation of these findings should indicate what is known about tDCS, and what remains to be found before it should be used outside of a controlled laboratory environment.