The monetary gambling task (MGT) used in this study is illustrated in Fig. 1. Each trial began with a choice stimulus (CS), with two numbers 10 (left box) and 50 (right box), with a monetary value in US cents, displayed for 800 ms. The participants select a bet of either 50¢ or 10¢, and receive feedback of either loss or gain for the selected amount (outcome stimulus, OS). The task details have been described in our previous publications (Kamarajan et al., 2008; Kamarajan et al., 2009; Kamarajan et al., 2010; Kamarajan et al., 2012). The inter-stimulus interval between a CS and OS, and between an OS and next CS is 1500 ms. The task involved a total of 172 trials, each with one of four possible outcomes: Loss 50, Loss 10, Gain 50, and Gain 10. P3 amplitudes were measured during the ERP epochs of outcome stimuli (1000 ms poststimulus) which contained the feedback of either loss or gain for each trial (i.e., the epochs following colored frames in Fig. 1).
