118 CHAPTER 6 of the stimulus with the current posture of the participant’s corresponding limb (Figure 2B) tests whether participants perform first-person motor imagery: i.e. whether stimuli that are incongruent with their own body posture elicit longer RTs and more activation in parietal areas compared to congruent postures. 24, 58 Trials started with a white fixation cross, followed by presentation of the stimulus in the centre of the screen, until a response was recorded (max 4000ms). The inter-trial interval varied randomly between 2000-3000ms. The task consisted of 256 trials in 32 blocks of 8, and took 20-30 minutes, depending on performance. The order of the trials was pseudorandomised, ensuring an even distribution of trial types across blocks. Prior to scanning, patients performed 4 blocks of 8 practice trials at a desktop computer. For the MRI-scan, patients lay on the scanner bed in a supine position, with their extended arms resting on the scanner bed, their thighs, or support pillows, and their head fixated in the MRI head coil with a piece of tape across their forehead to minimize movement. 128 Stimuli were presented on a screen visible through a mirror attached to the head coil. We monitored alertness with an eye-monitor. We acquired images on a 3T Siemens PrismaFit scanner (Siemens Healthcare, Erlangen, Germany), equipped with a 32-channel head coil. We acquired a T1-weighted anatomical scan with a Magnetization Prepared Rapid Gradient Echo (MPRAGE, TR = 2300 ms, TE = 3.03 ms, TI = 1100 ms, flip angle = 8˚, voxel size = 1.0 x 1.0 x 1.0 mm, slices = 192, FOV = 256 mm, scanning time = 5:21 min). During the task, we acquired functional images using a multiband 6 sequence (MB6, TR = 1000 ms, TE = 34 ms, acceleration factor = 6, flip angle = 60˚, voxel size = 2.019 x 2.019 x 2.000 mm, slices = 72, FOV = 210 mm, scanning time = 20-30 min varying with task performance). Figure 2 Experimental task design A. Overview of stimuli. Stimuli differed in laterality (left or right), view (back or palm of the hand), and were rotated at -135° to 135° with 30° increments. Stimuli with a medial orientation (rotated towards the body midline) are associated with biomechanically easy movement, whereas stimuli with a lateral orientation (rotated away from the body midline) are associated with biomechanically complex movement. B. POSTURAL CONGRUENCY at the start of each block, patients were instructed to assume a limb posture (with the hand palm either up or down). This posture could be either congruent (example on the left), or incongruent with the stimulus view (example on the right).