The alternating-current stimulation was administered noninvasively using an M x N 9-channel high-definition transcranial electrical current stimulator (Soterix Medical, New York, NY). The HD-tACS procedures included multiple sintered 12-mm diameter Ag/AgCl electrodes, attached to custom high-definition plastic holders, filled with conductive gel, and embedded in the BrainCap. Electrode placement was guided by current-flow modeling using HD-Explore and HD-Targets (Soterix Medical, New York, NY), with the goal of targeting the left prefrontal cortex and the left temporal cortex. The selection of these regions was based on a pilot study of ten subjects, in which data-driven coupling analyses (described below) identified the involvement of these regions during the memory versus non-mnemonic blocks of the change-detection task. Figure 1a shows the stimulation parameters (i.e., electrode number, electrode location, and current intensity values) of the multifocal frontotemporal inphase montages. Figure 5a shows the stimulation parameters of the unifocal frontal montage targeting left prefrontal cortex. Figure 5b shows the stimulation parameters of the unifocal temporal montage targeting the left temporal cortex. A bipolar sinusoidal alternating current was applied at either an individual subject defined theta-band
