2-P-D-17. Effect of unilateral transcranial direct current stimulation on contralateral cerebral blood flow changes during ipsilateral motor tasks

This study evaluated the cerebral blood flow changes during motor tasks performed before and after transcranial direct current stimulation (tDCS). Seven healthy volunteers (22.8 ± 2.0 years) received tDCS (anodal, cathodal, and sham) applied over the right primary motor cortex at 1 mA for 20 min. The second electrode was placed on the left supraorbital region. Subjects completed a tapping task using the right index finger with maximum effort before and after tDCS. The oxyhemoglobin concentration (O2Hb) was collected during the tapping task using 34-channel near-infrared spectroscopy positioned over the left (contralateral side to the tDCS and motor task) sensorimotor area. We calculated the O2Hb differences (ΔO2Hb) between before and after the tDCS. The finger tapping task induced an increase in O2Hb (about 0.01-0.015 mM cm) in the entire left sensorimotor area. However, the ΔO2Hb was not significant between the three conditions, as determined using a one-way analysis of variance (p = 0.556-0.870). These findings suggest that the cerebral blood flow changes induced in the left sensorimotor area by the finger tapping task were not affected by the tDCS applied to the right (ipsilateral to the motor task) primary motor cortex.