Effect of Transcranial Direct Current Stimulation on Working Memory

Working memory as a cognitive performance is responsible for keeping transient information and manipulating and using them in thinking process. Working memory, like other cognitive abilities, can be impaired due to various factors such as diseases, psychological disorders, and aging. Therefore, it is very important to find ways to compensate these weaknesses. Transcranial direct current stimulation, among the most recent proposed methods, seems to be a promising method. The aim of the present study was to investigate the effects of anodal transcranial direct current stimulation on working memory in healthy individuals.
Literature was searched for the studies investigating the effects of transcranial direct current stimulation on working memory in PubMed, Scopus, Science Direct, and Web of Knowledge databases from among the papers published between 2000-2018 using the following keywords: "Working memory", "Healthy people", "Dorsolateral prefrontal cortex", and "Transcranial direct current stimulation". Out of the 70 papers obtained, 36 articles were selected based on inclusion and exclusion criteria. Among those articles, 14 were specifically related to the subject of the present research and thus were further examined.
The results reported in most of the studies indicated that anodal transcranial direct current stimulation can significantly improve the performance of working memory. Also, the electrical stimulation, together with cognitive tasks, is more effective as compared with single electrical stimulation.
Transcranial direct current stimulation can improve cognitive performances, especially working memory in healthy people, by modulating the electrical activities in the dorsolateral prefrontal cortex. However, further studies are required, especially on the elderly population whose cognitive abilities are diminished with age.