A, The right lateralized 8-channel in-phase high definition transcranial alternating-current stimulation (HD-tACS) montage and current-flow model shown on 3D reconstructions of the cortical surface. The yellow (positive) and blue (negative) circles in the montage reflect the polarity of electrical current applied over medial frontal cortex (MFC) and right lateral prefrontal cortex (lPFC) target regions. B, The sequence of events on feedback and nonfeedback trials in the time estimation task. C, Performance measures of absolute error magnitude, response variability, and adjustment efficiency across blocks of feedback (gray) and nonfeedback (white) trials after the 6-Hz eyes closed (red), 6-Hz eyes open (blue), and 10-Hz eyes open (green) active conditions, and the sham (black) condition in the same subjects. Error bars show ± 1 standard error of the mean.