Between illumination conditions, a 3-min dark break was provided to avoid a possible carry-over effect from one illumination condition to another. The optical parameters were measured on the display monitor by a chromameter (CL-200A, Konica-Minolta, Japan). Although over 100 different versions of CPT could be in use (Greenberg and Waldman, 1993), participants Cobimetinib concentration in the present study were instructed to respond by pressing a button with one hand whenever the digit “0” appeared, which was the target stimulus. Furthermore, they were instructed to press a button with the opposite hand if one of the

remaining single digits (1–9) was presented. A single-digit number randomly drawn from a series of single digits (0–9) was presented (one at a time) on the display monitor for 1500 ms with a 2000 ms ISI. The number “0” was a target stimulus, with an appearance frequency

of 30%. The remaining see more 70% of stimuli was filled up with one of numerals from 1 to 9. Using a presentation-software (E-prime 2.0 Professional, Psychology Software Tools, USA), the target stimulus “0” was presented 90 times, and the non-target stimuli (1 to 9) were shown 210 times in the entire experiment. The stimulus-digit in gray (luminance: 30.55 cd/m2) subtended at 4° (visual angle) and was presented in a black background monitor (luminance: 0.93 cd/m2), most of which was covered with a white paper except the area for the stimulus presentation to remove any reflections on the monitor. The luminance contrast of the stimulus against Dipeptidyl peptidase the dark background illumination (luminance: 38.26 cd/m2) was 1/1.25; whereas that of the light background illumination (luminance: 169.9 cd/m2) was 1/5.56. Participants were required to press

a button as quickly as possible. Response hands were counterbalanced across participants. In order to enhance participants’ motivation for efficient task-performance, feedback results for task-performance (i.e., correct or incorrect) was presented automatically after each stimulus (Fig. 3B). During the CPT performance, EEG was measured, using a NuAmp amplifier (Neuroscan, USA) with 40 Ag/AgCl electrodes, the location of which was in accordance with the international 10–10 system. An electrode on each mastoid was placed for the linked reference, and a ground electrode at AFz. Eye movement activity was monitored with two pairs of electrodes placed, both vertically and horizontally, with respect to both eyes. Electrode impedances were maintained below 5 kΩ prior to data acquisition. EEG was sampled at 250 Hz (analog band-pass filter 0.1–100 Hz). Data were epoched from 1000 ms prestimulus to 1000 ms poststimulus. Epochs containing eye-movements or other artifacts (maximum amplitude ±100 μV or electrode drifts) were rejected. As a result, the average rejection rate was 10.27%. Only trials with correct responses were further analyzed.