To minimize learning effects, a practice run for each task was presented outside of the scanner. After the first scanning learn more session, subjects received 35 mg MPH (approximately 0.5 mg per kg body weight) to be taken orally with water. Subjects were then free to relax for 1.5 h until peek plasma levels were expected

(Swanson and Volkow, 2003) and then re-entered the MRI scanner for the second session that was identical to the first. MPH was obtained from Sandoz B.V. (Weesp, the Netherlands). All MR imaging was performed using a 3.0 T Philips MR scanner equipped with an SENSE 8-channel head coil and body coil transmission (Philips Medical Systems, Best, The Netherlands). The session protocol consisted of a high resolution

3D T1-weighted anatomical scan for registration and segmentation purposes and a fast single shot echo planar image (EPI) sequence for BOLD analysis. For the BOLD acquisition imaging parameters were: TR/TE 2300/30 ms; FOV 220 mm × 220 mm; 40 slices; voxel size 3 mm × 3 mm × 3 mm; no gap; 80° flip angle, SENSE Navitoclax order 2.0. The reward anticipation task was presented by a video projection system onto a white screen using E-prime software (Psychological Software Tools, USA). Subjects saw the screen via a mirror attached to the head coil. Responses were logged via a response box attached to the computer presenting the stimuli. Subjects were asked to imagine actually receiving the amounts displayed in the task, but did not receive click here any additional reward apart from their financial compensation for participation. We chose this option because playing for points or real money has led to similar results in reward response (Cole et al., 2012 and Peters et al., 2011). All subjects performed

a modified version of the monetary incentive delay task as described in Knutson et al. (2001). In the task the response to anticipation of gaining or losing money and a neutral condition was determined. Three graded positive cue stimuli signaled that, if the subjects responded on the subsequent target presentation, he would gain a monetary reward (36 trials), three graded negative stimuli signaled that, if the subject would not respond to the target presentation, he would loose money (36 trials). One neutral cue, finally, signaled no incentive outcome (18 trials). An indication on the stimulus signaled the size of the reward or loss (€0.00, €0.20, €1.00 or €5.00). Stimuli (presented for 250 ms) were presented in a pseudorandom order. Each cue was replaced by a cross-hair with variable delay during the anticipation period (2000–2500 ms). Thereafter, the target was presented for a variable length of time (160–260 ms) and subjects were instructed to respond as fast as possible to the target by pressing a button with their right index finger. Responding in time to the target would result in monetary gain or avoidance of loss.