Delay discounting.
For first-level, subject-wise analysis of the fMRI data we constructed 2 regressors of interest. The less-now regressor reflected γ-function-convolved δ functions during decision epochs when subjects decided to take less money made available that day. The more-later regressor reflected times at which subjects decided to take more money made available at the delay interval for that trial. The decision epoch for each trial was defined as the time from when choice stimuli were presented to when a response was made. The 2 regressors of interest spanned just this period of time. Response and feedback epochs for each trial were also modeled as regressors of no interest as were trials for decisions directly proximate to the indifference point. Pilot testing showed that clearer neural-functional effects were obtained by exclusion of these borderline decision trials.Group-level analyses were run using a similar 3dMVM approach as the MID task, using a factorial ANOVA with intervention (placebo/ghrelin) and choice (less-now/more-later) as 2 within subject factors. Furthermore, we examined relations between 