105 Neural effects of deep brain stimulation on reward and loss anticipation and food viewing in anorexia nervosa: a pilot study Measurements We conducted fMRI scans at three time-points: 1) pre-operatively at T-1 as a baseline measurement, 2) at the end of the optimization period (T2, to investigate short-term effects of stimulation), and 3) at 12 months after ending the optimization period (T4, at the end of the maintenance phase) (See figure 1). For controls, fMRI was conducted at three time-points as well, matching the time intervals of the AN group, however they did not receive DBS treatment. In addition to neurophysiological measures, we closely monitored patients clinically and psychologically during follow-up by means of BMI and psychiatric symptom questionnaires (1) . Figure 1. The temporal phases of the DBS treatment with the fMRI time-points at T-1, T2 and T4 Tasks The monetary reward task used motivational rewarding stimuli (31) in the form of cues predicting a rewarding, neutral or loss outcome. Each condition consisted of three different levels regarding the magnitude of the outcome to motivate participants and enhance reward uncertainty. The presentation of the cues, which constituted the reward anticipation phase, was followed by a target to which participants had to respond as fast as possible. After responding, participants received feedback on their final monetary rewarding, neutral or loss outcome. In case of a positive monetary rewarding outcome, the actual amount of money was provided. Time to respond was limited by individual reaction times collected before the experiment to create equal performance across participants. Trial conditions were counterbalanced at random order (36 trials per condition) and trial durations were randomly varied (6-10s per trial). The total duration of the task was 14 minutes. During the food viewing task, subjects were presented with images of non-food, high-calorie food and low-calorie food using a paradigm similar to previous studies conducted on both healthy subjects and anorexia patients (21, 33). We used standardized food and neutral pictures from the database developed by Charbonnier e.a. (34). The images were presented over six blocks with a duration of 30s per block. The blocks were pseudorandomized and alternately consisted of Figure 1. The temporal phases of the DBS treatment with the fMRI time-points at T-1, T2 and T4 T-1 Preopterative phase T0 Postoperative phase T1 Optimization phase (3-9 months) T2 Maintenance phase (6 months) T3 Maintenance phase (6 months) T4 End of trial fMRI T-1 fMRI T1 fMRI T4
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