Multifocal TDCS With Anodal Configuration Over Motor Cortex Induce Higher Excitability Than Cathodal Configuration

Based on recent research findings, endurance performance during incremental cycling depends on the level of cortical activation of the FC1-FC2-C1-C2 motor network. Indeed, a novel multifocal transcranial direct current stimulation (tDCS) protocol with different individual stimulation intensities and polarities to simultaneously target multi-different cortical areas has been used to modulate this specific area in order to enhance endurance capacity. PURPOSE: This study was designed to examine how multifocal tDCS affects cortical excitability and blood flow of specific areas. METHODS: Fifteen healthy participants (21.6 ± 2.91 yrs, 163.9 ± 6.62 cm, 53.5 ± 8.49 kg) received two types of 20 minutes multifocal tDCS with a seven-electrode montage targeting the motor cortex (FC1, FC2, C1, C2) and associated areas (AF7, P9 and PO7) based on electric-field modelling. They received either anodal or cathodal currents over the motor cortex electrodes. Anodal motor stimulation was consisted of FC1(1.221 mA), FC2(0.954 mA), C1(1.053 mA), C2(0.77 mA), AF7(-1.016 mA), P9(-1.430 mA), and PO7(-1.552 mA), and cathodal was consisted of FC1(-1.221 mA), FC2(-0.954 mA), C1(-1.053 mA), C2(-0.77 mA), AF7(1.016 mA), P9(1.430 mA), and PO7(1.552 mA). The functional near-infrared spectroscopy was used to assess the cortical excitability and blood flow during tDCS by measuring the concentrations of oxygenated (HbO) and total hemoglobin (THb) respectively. RESULTS: Anodal motor cortex stimulation resulted in significantly higher HbO in FC1 (t = 2.92, p = 0.015), FC2 (t = 3.37, p = 0.007), and C2 (t = 2.44, p = 0.035), and significantly higher THb in C2 (t = 2.24, p = 0.049) than cathodal motor cortex stimulation, but no differences were observed in other areas. CONCLUSIONS: Multifocal tDCS with anodal configuration induces cortical excitability increases in majority of specific cortical areas, while having less effect on blood flow. Therefore, using multifocal tDCS with anodal configuration might induce more promising modulation effects in enhancing endurance capacity. This study is supported by China Scholarship Council and the key program of the Natural Science Foundation of China (11932013).