of four possible colors (yellow, blue, red, green) and the word color order was pseudo randomized. Subjects were instructed to press one of four buttons (yellow, blue, red, green) of the MRI-compatible Lumina LP-400 response pad (Cedrus Corp., San Pedro, CA) during the response window matching the color of the word. A fixation cross against a black background was presented during the three 20-seconds long resting baseline epochs and subjects were instructed to not press any button and rest motionless as possible during these epochs. Thus, each sequence (“drug” or “neutral”) was 206 seconds long. The task was developed in E-prime (Psychology Software Tools, Inc., Pittsburgh, PA) and used a trigger pulse from the MRI console for precise synchronization with fMRI acquisition.
