Application of Triangular Waveform for Transcranial Alternating Current Stimulation in Working Memory

Transcranial alternating current stimulation (tACS) provides a technical means to non-invasively modulate cortical oscillations. Compared to the sinusoidal current used in most studies, the triangular current has lower energy consumption. Here we report a 40 Hz tACS protocol with a triangular current to investigate its effects on N-back working memory (WM) in healthy adults. Significant differences of WM performance were observed between pre- and post-stimulation across all conditions and tasks, however, the rate of WM performance improvements were only observed in 3-back task between tACS and sham condition. The event-related potentials (ERPs) analysis showed that triangular-tACS could change the electroencephalogram (EEG) components of different tasks. The P300 component in the right prefrontal cortex increases after stimulation in the 2-back task, while the P200 component in the left parietal cortex decreases in the 3-back task. Moreover, triangular-tACS also increases theta power in the left frontal and posterior parietal cortex. Our findings demonstrate that triangular-tACS have an active impact on the WM performance.