Functional Differences in Effortful Control

The purpose of this study was to learn more about the brain circuits involved with effortful control in healthy adult participants. It was planned that the study would enroll 80 participants to a dual task paradigm pilot while undergoing a fMRI scan to assess brain mechanisms that cause the "depletion effect". This effect refers to the observation that people perform more poorly on effortful control tasks after they have already performed task requiring effortful control. Then subsequent study participants would be given either methylphenidate (also known as 'Ritalin') which is FDA approved and the most widely-used medication for Attention Deficit Hyperactivity Disorder (ADHD) or a placebo, which is a sugar pill. Each participant would also perform some computer tasks that have been shown in previous studies to require effortful control while undergoing an fMRI (functional Magnetic Resonance Imaging) which takes a special kind of picture of the brain. The study's goal was to learn more about the brain mechanisms by which methylphenidate improves effortful control. After enrolling the first 50 participants, the study assessed whether a depletion effect was observed in the dual task paradigm. It was found that there was not: there was no statistically significant difference in effortful control performance comparing subjects who did and did not perform a prior effortful control task. Because the behavioral manipulation failed, it was determined that the drug manipulation portion of the study was no longer justified. Thus, after enrolling 50 participants to the pilot part of the study, the decision was made to terminate the study without beginning the trial of methylphenidate.