fMRI: All of the MR images will be acquired on a 3.0 T scanner using an 8-channel head coil. T1-weighted brain volume (BRAVO) acquisitions will evaluate gray matter (GM) volume and thickness, markers of brain atrophy. This sequence will measure the ratio of GM within the PFC to overall GM, which will then be used to quantify the level of activation within the PFC. T2* echo planner imaging acquisition will be used for all the DT paradigms including intrinsic functional connectivity. Intrinsic connectivity will be examined while subjects are not engaged in any particular task and are requested to lie still with their eyes open (i.e., resting state). To examine task related changes versus more generalized patterns of DT activations, the type of the cognitive task or the nature of the motor task will be different in each task. The researchers will specifically examine the contribution of a secondary task involving working memory (arithmetic processing vs. attention), conflict monitoring, and motor planning on DT related activations.