Targeting the anterior cingulate with bipolar and high-definition transcranial direct current stimulation.

Research on the feasibility of using transcranial direct current stimulation to modulate the function of the anterior cingulate cortex is limited in part due to its anatomical depth. However, high-definition transcranial direct current stimulation may be better able to reach the anterior cingulate cortex and modulate its function and behavioral outputs. The purpose of this study was to assess the feasibility of using high-definition transcranial direct current stimulation, as compared to traditional bipolar transcranial direct current stimulation, to modulate behavioral measures of anterior cingulate cortex function. In a mixed design, 36 participants received either high-definition transcranial direct current stimulation or bipolar transcranial direct current stimulation, and experienced anodal, cathodal, and sham stimulation over the course of three visits. Two behavioral tasks were used to assess anterior cingulate cortex function before and after stimulation: the multi-source interference task and an emotional facial expression interference task. High-definition transcranial direct current stimulation and bipolar transcranial direct current stimulation groups did not differ in their performance (as measured via response times and error rates) on either task. High-definition transcranial direct current stimulation and bipolar transcranial direct current stimulation were similarly ineffective in modulating behavior related to the anterior cingulate cortex. Future research should explore other transcranial direct current stimulation montages including extracephalic montages (e.g. shoulder, neck) for targeted stimulation of the anterior cingulate cortex.