Perception and pain thresholds of tDCS and tACS.

Abstract

Transcranial electric stimulation (tES) protocols strictly need to keep the safety of stimulations and to avoid the unpleasant feelings of stimulated subjects. Following that, the aim of the paper was to find out both the perception and the pain thresholds of different tES modalities. The perception thresholds and the pain thresholds at AF7 and AF8 electrodes with transcranial direct and alternating current stimulation (tDCS and tACS) were performed. Average perception and pain thresholds did not differ significantly inter-individually but intra-individually. With gradually increasing intensity the analysis of thresholds showed that 1) an average participant perceived as first 20 Hz and 40 Hz tACS, then 10 Hz tACS and cathodal tDCS and then anodal tDCS, and 2) the pain was felt first for anodal tDCS, then for 6, 10 and 20 Hz tACS, then for cathodal tDCS and finally for 40 Hz tACS. Besides that, intensity-dependent regularities in feelings of different tES modalities were found. Perception thresholds for 2 types of tDCS (anodal and cathodal) and 4 types of tACS (6-40 Hz) are arranged in sequence of gradually increased values (threshold current): anodal tDCS - cathodal tDCS - 6 - 10 - 20 - 40 Hz tACS. whereas pain thresholds are arranged with decreased threshold values.