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.