2.3 Experimental apparatus
During the experiment, participants were seated in a dim room with a 0.25 cd/m² luminance level with a chin rest at 60 cm from the 24-inch LCD monitor. The task was programmed using Matlab 2021b and Psychtoolbox-3 (Brainard, 1997; Kleiner et al., 2007; Pelli, 1997), allowing precise control over stimulus presentation. otDCS and tACS were delivered with the Geodesic Transcranial Electrical Neuromodulation (GTEN) Planning Module (Magstim Electrical Geodesics, Inc., USA) through a 128-channel elastic cap. A total of 20 electrodes on the posterior sites were selected to serve the current delivery. The electrode numbers in the EGI system (corresponding 10-10 system electrode name) are 60, 66, 67(PO3), 71, 62(Pz), 72(POz), 76, 77(PO4), 84, 85(P2), and 69, 73, 70(O1), 74, 75(Oz), 81, 82, 83(O2), 88, 89). Conductive gel was applied for electrode-delivered stimulations to reduce electrode impedance, and anesthetic spray was applied to these electrodes to decrease tactile perception induced by stimulation.