The influence of theta transcranial alternating current stimulation (tACS) on working memory storage and processing functions.

The study aimed to explore the role of the fronto-parietal brain network in working memory function--in temporary storage and manipulation of information. In a single blind sham controlled experiment 36 respondents solved different working memory tasks after theta transcranial alternating current stimulation (tACS) was applied to left frontal, left parietal and right parietal areas. Both verum tACS protocols stimulating parietal brain areas (target electrodes positioned at location P3, or P4) had a positive effect on WM storage capacity as compared with sham tACS, whereas no such influence was observed for the stimulation of the left frontal area (target electrode positioned at location F3). A second finding was that left parietal theta tACS had a more pronounced influence on backward recall than on forward recall, which was not related to task content (spatial or verbal). The influence of theta tACS on WM executive processes was most pronounced for right parietal stimulation. The results are discussed in the broad theoretical framework of the multicomponent model of working memory.